Anand Jain [Tue, 10 Aug 2021 15:23:44 +0000 (23:23 +0800)]
btrfs: fix upper limit for max_inline for page size 64K
The mount option max_inline ranges from 0 to the sectorsize (which is
now equal to page size). But we parse the mount options too early and
before the actual sectorsize is read from the superblock. So the upper
limit of max_inline is unaware of the actual sectorsize and is limited
by the temporary sectorsize 4096, even on a system where the default
sectorsize is 64K.
Fix this by reading the superblock sectorsize before the mount option
parse.
Reported-by: Alexander Tsvetkov <alexander.tsvetkov@oracle.com> CC: stable@vger.kernel.org # 5.4+ Signed-off-by: Anand Jain <anand.jain@oracle.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
This happens when close_ctree is called while a dev_replace hasn't
completed. In close_ctree, we suspend the dev_replace, but keep the
replace target around so that we can resume the dev_replace procedure
when we mount the root again. This is the call trace:
However, since the replace target sticks around, there is a device
with BTRFS_DEV_STATE_REPLACE_TGT set on close, and we fail the
assertion in btrfs_close_one_device.
To fix this, if we come across the replace target device when
closing, we should properly reset it back to allocation state. This
fix also ensures that if a non-target device has a corrupted state and
has the BTRFS_DEV_STATE_REPLACE_TGT bit set, the assertion will still
catch the error.
Reported-by: David Sterba <dsterba@suse.com> Fixes: 63c9acd5c56c ("btrfs: fix rw device counting in __btrfs_free_extra_devids") CC: stable@vger.kernel.org # 4.19+ Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_lookup_ordered_extent() is supposed to query the offset in a file
instead of the logical address. Pass the file offset from
submit_extent_page() to calc_bio_boundaries().
Also, calc_bio_boundaries() relies on the bio's operation flag, so move
the call site after setting it.
Fixes: 83885a095e74 ("btrfs: refactor submit_extent_page() to make bio and its flag tracing easier") Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 11 Aug 2021 18:37:16 +0000 (14:37 -0400)]
btrfs: do not do preemptive flushing if the majority is global rsv
A common characteristic of the bug report where preemptive flushing was
going full tilt was the fact that the vast majority of the free metadata
space was used up by the global reserve. The hard 90% threshold would
cover the majority of these cases, but to be even smarter we should take
into account how much of the outstanding reservations are covered by the
global block reserve. If the global block reserve accounts for the vast
majority of outstanding reservations, skip preemptive flushing, as it
will likely just cause churn and pain.
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212185 Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 11 Aug 2021 18:37:15 +0000 (14:37 -0400)]
btrfs: reduce the preemptive flushing threshold to 90%
The preemptive flushing code was added in order to avoid needing to
synchronously wait for ENOSPC flushing to recover space. Once we're
almost full however we can essentially flush constantly. We were using
98% as a threshold to determine if we were simply full, however in
practice this is a really high bar to hit. For example reports of
systems running into this problem had around 94% usage and thus
continued to flush. Fix this by lowering the threshold to 90%, which is
a more sane value, especially for smaller file systems.
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212185 CC: stable@vger.kernel.org # 5.12+ Fixes: e17432c33757 ("btrfs: improve preemptive background space flushing") Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: tree-log: check btrfs_lookup_data_extent return value
Function btrfs_lookup_data_extent calls btrfs_search_slot to verify if
the EXTENT_ITEM exists in the extent tree. btrfs_search_slot can return
values bellow zero if an error happened.
Function replay_one_extent currently checks if the search found
something (0 returned) and increments the reference, and if not, it
seems to evaluate as 'not found'.
Fix the condition by checking if the value was bellow zero and return
early.
Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Thu, 29 Jul 2021 17:52:46 +0000 (18:52 +0100)]
btrfs: avoid unnecessarily logging directories that had no changes
There are several cases where when logging an inode we need to log its
parent directories or logging subdirectories when logging a directory.
There are cases however where we end up logging a directory even if it was
not changed in the current transaction, no dentries added or removed since
the last transaction. While this is harmless from a functional point of
view, it is a waste time as it brings no advantage.
One example where this is triggered is the following:
This last fsync ends up logging directories A, B and C, however we only
need to log directory A, as B and C were not changed since the last
transaction commit.
So fix this by changing need_log_inode(), to return false in case the
given inode is a directory and has a ->last_trans value smaller than the
current transaction's ID.
Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Now that we converted btrfs internally to account for idmapped mounts
allow the creation of idmapped mounts on by setting the FS_ALLOW_IDMAP
flag. We only need to raise this flag on the btrfs_root_fs_type
filesystem since btrfs_mount_root() is ultimately responsible for
allocating the superblock and is called into from btrfs_mount()
associated with btrfs_fs_type.
The conversion of the btrfs inode operations was straightforward.
Regarding btrfs specific ioctls that perform checks based on inode
permissions only those have been allowed that are not filesystem wide
operations and hence can be reasonably charged against a specific mount.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Make the ACL code idmapped mount aware. The POSIX default and POSIX
access ACLs are the only ACLs other than some specific xattrs that take
DAC permissions into account. On an idmapped mount they need to be
translated according to the mount's userns. The main change is done to
__btrfs_set_acl() which is responsible for translating POSIX ACLs to
their final on-disk representation.
The btrfs_init_acl() helper does not need to take the idmapped mount
into account since it is called in the context of file creation
operations (mknod, create, mkdir, symlink, tmpfile) and is used for
btrfs_init_inode_security() to copy POSIX default and POSIX access
permissions from the parent directory. These ACLs need to be inherited
unmodified from the parent directory. This is identical to what we do
for ext4 and xfs.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
The INO_LOOKUP_USER is an unprivileged version of the INO_LOOKUP ioctl
and has the following restrictions. The main difference between the two
is that INO_LOOKUP is filesystem wide operation wheres INO_LOOKUP_USER
is scoped beneath the file descriptor passed with the ioctl.
Specifically, INO_LOOKUP_USER must adhere to the following restrictions:
- The caller must be privileged over each inode of each path component
for the path they are trying to lookup.
- The path for the subvolume the caller is trying to lookup must be reachable
from the inode associated with the file descriptor passed with the ioctl.
The second condition makes it possible to scope the lookup of the path
to the mount identified by the file descriptor passed with the ioctl.
This allows us to enable this ioctl on idmapped mounts.
Specifically, this is possible because all child subvolumes of a parent
subvolume are reachable when the parent subvolume is mounted. So if the
user had access to open the parent subvolume or has been given the fd
then they can lookup the path if they had access to it provided they
were privileged over each path component.
Note, the INO_LOOKUP_USER ioctl allows a user to learn the path and name
of a subvolume even though they would otherwise be restricted from doing
so via regular VFS-based lookup.
So think about a parent subvolume with multiple child subvolumes.
Someone could mount he parent subvolume and restrict access to the child
subvolumes by overmounting them with empty directories. At this point
the user can't traverse the child subvolumes and they can't open files
in the child subvolumes. However, they can still learn the path of
child subvolumes as long as they have access to the parent subvolume by
using the INO_LOOKUP_USER ioctl.
The underlying assumption here is that it's ok that the lookup ioctls
can't really take mounts into account other than the original mount the
fd belongs to during lookup. Since this assumption is baked into the
original INO_LOOKUP_USER ioctl we can extend it to idmapped mounts.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Setting flags on subvolumes or snapshots are core features of btrfs. The
SUBVOL_SETFLAGS ioctl is especially important as it allows to make
subvolumes and snapshots read-only or read-write. Allow setting flags on
btrfs subvolumes and snapshots on idmapped mounts. This is a fairly
straightforward operation since all the permission checking helpers are
already capable of handling idmapped mounts. So we just need to pass
down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
The SET_RECEIVED_SUBVOL ioctls are used to set information about
a received subvolume. Make it possible to set information about a
received subvolume on idmapped mounts. This is a fairly straightforward
operation since all the permission checking helpers are already capable
of handling idmapped mounts. So we just need to pass down the mount's
userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: relax restrictions for SNAP_DESTROY_V2 with subvolids
So far we prevented the deletion of subvolumes and snapshots using
subvolume ids possible with the BTRFS_SUBVOL_SPEC_BY_ID flag.
This restriction is necessary on idmapped mounts as this allows
filesystem wide subvolume and snapshot deletions and thus can escape the
scope of what's exposed under the mount identified by the fd passed with
the ioctl.
Deletion by subvolume id works by looking for an alias of the parent of
the subvolume or snapshot to be deleted. The parent alias can be
anywhere in the filesystem. However, as long as the alias of the parent
that is found is the same as the one identified by the file descriptor
passed through the ioctl we can allow the deletion.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Destroying subvolumes and snapshots are important features of btrfs.
Both operations are available to unprivileged users if the filesystem
has been mounted with the "user_subvol_rm_allowed" mount option. Allow
subvolume and snapshot deletion on idmapped mounts. This is a fairly
straightforward operation since all the permission checking helpers are
already capable of handling idmapped mounts. So we just need to pass
down the mount's userns.
Subvolumes and snapshots can either be deleted by specifying their name
or - if BTRFS_IOC_SNAP_DESTROY_V2 is used - by their subvolume or
snapshot id if the BTRFS_SUBVOL_SPEC_BY_ID is set.
This feature is blocked on idmapped mounts as this allows filesystem
wide subvolume deletions and thus can escape the scope of what's exposed
under the mount identified by the fd passed with the ioctl.
This means that even the root or CAP_SYS_ADMIN capable user can't delete
a subvolume via BTRFS_SUBVOL_SPEC_BY_ID. This is intentional.
The root user is currently already subject to permission checks in
btrfs_may_delete() including whether the inode's i_uid/i_gid of the
directory the subvolume is located in have a mapping in the caller's
idmapping. For this to fail isn't currently possible since a btrfs
filesystem can't be mounted with a non-initial idmapping but it shows
that even the root user would fail to delete a subvolume if the relevant
inode isn't mapped in their idmapping. The idmapped mount case is the
same in principle.
This isn't a huge problem a root user wanting to delete arbitrary
subvolumes can just always create another (even detached) mount without
an idmapping attached.
In addition, we will allow BTRFS_SUBVOL_SPEC_BY_ID for cases where the
subvolume to delete is directly located under inode referenced by the fd
passed for the ioctl() in a follow-up commit.
Here is an example where a btrfs subvolume is deleted through a
subvolume mount that does not expose the subvolume to be delete but it
can still be deleted by using the subvolume id:
/* Compile the following program as "delete_by_spec". */
truncate -s 10G btrfs.img
mkfs.btrfs btrfs.img
export LOOPDEV=$(sudo losetup -f --show btrfs.img)
mount ${LOOPDEV} /mnt
sudo chown $(id -u):$(id -g) /mnt
btrfs subvolume create /mnt/A
btrfs subvolume create /mnt/B/C
# Get subvolume id via:
sudo btrfs subvolume show /mnt/A
# Save subvolid
SUBVOLID=<nr>
sudo umount /mnt
sudo mount ${LOOPDEV} -o subvol=B/C,user_subvol_rm_allowed /mnt
./delete_by_spec /mnt ${SUBVOLID}
With idmapped mounts this can potentially be used by users to delete
subvolumes/snapshots they would otherwise not have access to as the
idmapping would be applied to an inode that is not exposed in the mount
of the subvolume.
The fact that this is a filesystem wide operation suggests it might be a
good idea to expose this under a separate ioctl that clearly indicates
this. In essence, the file descriptor passed with the ioctl is merely
used to identify the filesystem on which to operate when
BTRFS_SUBVOL_SPEC_BY_ID is used.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Creating subvolumes and snapshots is one of the core features of btrfs
and is even available to unprivileged users. Make it possible to use
subvolume and snapshot creation on idmapped mounts. This is a fairly
straightforward operation since all the permission checking helpers are
already capable of handling idmapped mounts. So we just need to pass
down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: check whether fsgid/fsuid are mapped during subvolume creation
When a new subvolume is created btrfs currently doesn't check whether
the fsgid/fsuid of the caller actually have a mapping in the user
namespace attached to the filesystem. The VFS always checks this to make
sure that the caller's fsgid/fsuid can be represented on-disk. This is
most relevant for filesystems that can be mounted inside user namespaces
but it is in general a good hardening measure to prevent unrepresentable
gid/uid from being written to disk.
Since we want to support idmapped mounts for btrfs ioctls to create
subvolumes in follow-up patches this becomes important since we want to
make sure the fsgid/fsuid of the caller as mapped according to the
idmapped mount can be represented on-disk. Simply add the missing
fsuidgid_has_mapping() line from the VFS may_create() version to
btrfs_may_create().
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Enable btrfs_permission() to handle idmapped mounts. This is just a
matter of passing down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Enable btrfs_setattr() to handle idmapped mounts. This is just a matter
of passing down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Enable btrfs_tmpfile() to handle idmapped mounts. This is just a matter
of passing down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Enable btrfs_symlink() to handle idmapped mounts. This is just a matter
of passing down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Enable btrfs_mkdir() to handle idmapped mounts. This is just a matter of
passing down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Enable btrfs_create() to handle idmapped mounts. This is just a matter
of passing down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Enable btrfs_mknod() to handle idmapped mounts. This is just a matter of
passing down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Enable btrfs_getattr() to handle idmapped mounts. This is just a matter
of passing down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Enable btrfs_rename() to handle idmapped mounts. This is just a matter
of passing down the mount's userns.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Extend btrfs_new_inode() to take the idmapped mount into account when
initializing a new inode. This is just a matter of passing down the
mount's userns. The rest is taken care of in inode_init_owner(). This is
a preliminary patch to make the individual btrfs inode operations
idmapped mount aware.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Various filesystems rely on the lookup_one_len() helper to lookup a
single path component relative to a well-known starting point. Allow
such filesystems to support idmapped mounts by adding a version of this
helper to take the idmap into account when calling inode_permission().
This change is a required to let btrfs (and other filesystems) support
idmapped mounts.
Cc: Christoph Hellwig <hch@infradead.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: David Sterba <dsterba@suse.com>
Anand Jain [Tue, 10 Aug 2021 13:55:59 +0000 (21:55 +0800)]
btrfs: sysfs: document structures and their associated files
Sysfs file has grown big. It takes some time to locate the correct
struct attribute to add new files. Create a table and map the struct
attribute to its sysfs path.
Also, fix the comment about the debug sysfs path. And add the comments
to the attributes instead of attribute group, where sysfs file names are
defined.
Signed-off-by: Anand Jain <anand.jain@oracle.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
[CAUSE]
Commit dd4235fb0aa1 ("btrfs: Make btrfs_find_device_by_devspec return
btrfs_device directly") moves the "missing" device path check into
btrfs_rm_device().
But btrfs_rm_device() itself can have case where it only receives
@devid, with NULL as @device_path.
In that case, calling strcmp() on NULL will trigger the NULL pointer
dereference.
Before that commit, we handle the "missing" case inside
btrfs_find_device_by_devspec(), which will not check @device_path at all
if @devid is provided, thus no way to trigger the bug.
[FIX]
Before calling strcmp(), also make sure @device_path is not NULL.
Naohiro Aota [Mon, 9 Aug 2021 00:29:18 +0000 (09:29 +0900)]
btrfs: zoned: add asserts on splitting extent_map
We call split_zoned_em() on an extent_map on submitting a bio for it. Thus,
we can assume the extent_map is PINNED, not LOGGING, and in the modified
list. Add ASSERT()s to ensure the extent_maps after the split also has the
proper flags set and are in the modified list.
Suggested-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
Naohiro Aota [Mon, 9 Aug 2021 04:13:44 +0000 (13:13 +0900)]
btrfs: zoned: fix block group alloc_offset calculation
alloc_offset is offset from the start of a block group and @offset is
actually an address in logical space. Thus, we need to consider
block_group->start when calculating them.
Fixes: e46eb1682614 ("btrfs: zoned: advance allocation pointer after tree log node") CC: stable@vger.kernel.org # 5.12+ Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
Naohiro Aota [Mon, 9 Aug 2021 04:32:30 +0000 (13:32 +0900)]
btrfs: zoned: suppress reclaim error message on EAGAIN
btrfs_relocate_chunk() can fail with -EAGAIN when e.g. send operations are
running. The message can fail btrfs/187 and it's unnecessary because we
anyway add it back to the reclaim list.
btrfs: zoned: allow disabling of zone auto reclaim
Automatically reclaiming dirty zones might not always be desired for all
workloads, especially as there are currently still some rough edges with
the relocation code on zoned filesystems.
Allow disabling zone auto reclaim on a per filesystem basis by writing 0
as the threshold value.
Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Thu, 29 Jul 2021 14:30:21 +0000 (15:30 +0100)]
btrfs: update comment at log_conflicting_inodes()
A comment at log_conflicting_inodes() mentions that we check the inode's
logged_trans field instead of using btrfs_inode_in_log() because the field
last_log_commit is not updated when we log that an inode exists and the
inode has the full sync flag (BTRFS_INODE_NEEDS_FULL_SYNC) set. The part
about the full sync flag is not true anymore since commit abd50ab58fb998
("btrfs: fix unpersisted i_size on fsync after expanding truncate"), so
update the comment to not mention that part anymore.
Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Thu, 29 Jul 2021 14:29:01 +0000 (15:29 +0100)]
btrfs: remove no longer needed full sync flag check at inode_logged()
Now that we are checking if the inode's logged_trans is 0 to detect the
possibility of the inode having been evicted and reloaded, the test for
the full sync flag (BTRFS_INODE_NEEDS_FULL_SYNC) is no longer needed at
tree-log.c:inode_logged(). Its purpose was to detect the possibility
of a previous eviction as well, since when an inode is loaded the full
sync flag is always set on it (and only cleared after the inode is
logged).
So just remove the check and update the comment. The check for the inode's
logged_trans being 0 was added recently by the patch with the subject
"btrfs: eliminate some false positives when checking if inode was logged".
Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Thu, 29 Jul 2021 14:28:34 +0000 (15:28 +0100)]
btrfs: remove unnecessary NULL check for the new inode during rename exchange
At the very end of btrfs_rename_exchange(), in case an error happened, we
are checking if 'new_inode' is NULL, but that is not needed since during a
rename exchange, unlike regular renames, 'new_inode' can never be NULL,
and if it were, we would have a crashed much earlier when we dereference it
multiple times.
So remove the check because it is not necessary and because it is causing
static checkers to emit a warning. I probably introduced the check by
copy-pasting similar code from btrfs_rename(), where 'new_inode' can be
NULL, in commit 024d26ba723434 ("Btrfs: unpin logs if rename exchange
operation fails").
Reported-by: kernel test robot <lkp@intel.com> Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: allocate btrfs_ioctl_defrag_range_args on stack
Instead of using kmalloc() to allocate btrfs_ioctl_defrag_range_args,
allocate btrfs_ioctl_defrag_range_args on stack, the size is reasonably
small and ioctls are called in process context.
sizeof(btrfs_ioctl_defrag_range_args) = 48
Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: allocate btrfs_ioctl_quota_rescan_args on stack
Instead of using kmalloc() to allocate btrfs_ioctl_quota_rescan_args,
allocate btrfs_ioctl_quota_rescan_args on stack, the size is reasonably
small and ioctls are called in process context.
sizeof(btrfs_ioctl_quota_rescan_args) = 64
Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
It's a common practice to start a search using offset (u64)-1, which is
the u64 maximum value, meaning that we want the search_slot function to
be set in the last item with the same objectid and type.
Once we are in this position, it's a matter to start a search backwards
by calling btrfs_previous_item, which will check if we'll need to go to
a previous leaf and other necessary checks, only to be sure that we are
in last offset of the same object and type.
The new btrfs_search_backwards function does the all these steps when
necessary, and can be used to avoid code duplication.
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Boris Burkov [Wed, 30 Jun 2021 20:01:50 +0000 (13:01 -0700)]
btrfs: verity metadata orphan items
Writing out the verity data is too large of an operation to do in a
single transaction. If we are interrupted before we finish creating
fsverity metadata for a file, or fail to clean up already created
metadata after a failure, we could leak the verity items that we already
committed.
To address this issue, we use the orphan mechanism. When we start
enabling verity on a file, we also add an orphan item for that inode.
When we are finished, we delete the orphan. However, if we are
interrupted midway, the orphan will be present at mount and we can
cleanup the half-formed verity state.
There is a possible race with a normal unlink operation: if unlink and
verity run on the same file in parallel, it is possible for verity to
succeed and delete the still legitimate orphan added by unlink. Then, if
we are interrupted and mount in that state, we will never clean up the
inode properly. This is also possible for a file created with O_TMPFILE.
Check nlink==0 before deleting to avoid this race.
A final thing to note is that this is a resurrection of using orphans to
signal an operation besides "delete this inode". The old case was to
signal the need to do a truncate. That case still technically applies
for mounting very old file systems, so we need to take some care to not
clobber it. To that end, we just have to be careful that verity orphan
cleanup is a no-op for non-verity files.
Signed-off-by: Boris Burkov <boris@bur.io> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Boris Burkov [Wed, 30 Jun 2021 20:01:49 +0000 (13:01 -0700)]
btrfs: initial fsverity support
Add support for fsverity in btrfs. To support the generic interface in
fs/verity, we add two new item types in the fs tree for inodes with
verity enabled. One stores the per-file verity descriptor and btrfs
verity item and the other stores the Merkle tree data itself.
Verity checking is done in end_page_read just before a page is marked
uptodate. This naturally handles a variety of edge cases like holes,
preallocated extents, and inline extents. Some care needs to be taken to
not try to verity pages past the end of the file, which are accessed by
the generic buffered file reading code under some circumstances like
reading to the end of the last page and trying to read again. Direct IO
on a verity file falls back to buffered reads.
Verity relies on PageChecked for the Merkle tree data itself to avoid
re-walking up shared paths in the tree. For this reason, we need to
cache the Merkle tree data. Since the file is immutable after verity is
turned on, we can cache it at an index past EOF.
Use the new inode ro_flags to store verity on the inode item, so that we
can enable verity on a file, then rollback to an older kernel and still
mount the file system and read the file. Since we can't safely write the
file anymore without ruining the invariants of the Merkle tree, we mark
a ro_compat flag on the file system when a file has verity enabled.
Acked-by: Eric Biggers <ebiggers@google.com> Co-developed-by: Chris Mason <clm@fb.com> Signed-off-by: Chris Mason <clm@fb.com> Signed-off-by: Boris Burkov <boris@bur.io> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Boris Burkov [Wed, 30 Jun 2021 20:01:48 +0000 (13:01 -0700)]
btrfs: add ro compat flags to inodes
Currently, inode flags are fully backwards incompatible in btrfs. If we
introduce a new inode flag, then tree-checker will detect it and fail.
This can even cause us to fail to mount entirely. To make it possible to
introduce new flags which can be read-only compatible, like VERITY, we
add new ro flags to btrfs without treating them quite so harshly in
tree-checker. A read-only file system can survive an unexpected flag,
and can be mounted.
As for the implementation, it unfortunately gets a little complicated.
The on-disk representation of the inode, btrfs_inode_item, has an __le64
for flags but the in-memory representation, btrfs_inode, uses a u32.
David Sterba had the nice idea that we could reclaim those wasted 32 bits
on disk and use them for the new ro_compat flags.
It turns out that the tree-checker code which checks for unknown flags
is broken, and ignores the upper 32 bits we are hoping to use. The issue
is that the flags use the literal 1 rather than 1ULL, so the flags are
signed ints, and one of them is specifically (1 << 31). As a result, the
mask which ORs the flags is a negative integer on machines where int is
32 bit twos complement. When tree-checker evaluates the expression:
The mask is something like 0x80000abc, which gets promoted to u64 with
sign extension to 0xffffffff80000abc. Negating that 64 bit mask leaves
all the upper bits zeroed, and we can't detect unexpected flags.
This suggests that we can't use those bits after all. Luckily, we have
good reason to believe that they are zero anyway. Inode flags are
metadata, which is always checksummed, so any bit flips that would
introduce 1s would cause a checksum failure anyway (excluding the
improbable case of the checksum getting corrupted exactly badly).
Further, unless the 1 << 31 flag is used, the cast to u64 of the 32 bit
inode flag should preserve its value and not add leading zeroes
(at least for twos complement). The only place that flag
(BTRFS_INODE_ROOT_ITEM_INIT) is used is in a special inode embedded in
the root item, and indeed for that inode we see 0xffffffff80000000 as
the flags on disk. However, that inode is never seen by tree checker,
nor is it used in a context where verity might be meaningful.
Theoretically, a future ro flag might cause trouble on that inode, so we
should proactively clean up that mess before it does.
With the introduction of the new ro flags, keep two separate unsigned
masks and check them against the appropriate u32. Since we no longer run
afoul of sign extension, this also stops writing out 0xffffffff80000000
in root_item inodes going forward.
Signed-off-by: Boris Burkov <boris@bur.io> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: simplify return values in btrfs_check_raid_min_devices
Function btrfs_check_raid_min_devices() returns error code from the enum
btrfs_err_code and it starts from 1. So there is no need to check if ret
is > 0. So drop this check and also drop the local variable ret.
Signed-off-by: Anand Jain <anand.jain@oracle.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: remove the dead comment in writepage_delalloc()
When btrfs_run_delalloc_range() failed, we will error out.
But there is a strange comment mentioning that
btrfs_run_delalloc_range() could have returned value >0 to indicate the
IO has already started.
Commit e8a5c2e49929 ("Btrfs: split up __extent_writepage to lower stack
usage") introduced the comment, but unfortunately at that time, we were
already using @page_started to indicate that case, and still return 0.
Furthermore, even if that comment was right (which is not), we would
return -EIO if the IO had already started.
By all means the comment is incorrect, just remove the comment along
with the dead check.
Just to be extra safe, add an ASSERT() in btrfs_run_delalloc_range() to
make sure we either return 0 or error, no positive return value.
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
David Sterba [Thu, 22 Jul 2021 18:54:37 +0000 (20:54 +0200)]
btrfs: allow degenerate raid0/raid10
The data on raid0 and raid10 are supposed to be spread over multiple
devices, so the minimum constraints are set to 2 and 4 respectively.
This is an artificial limit and there's some interest to remove it.
Change this to allow raid0 on one device and raid10 on two devices. This
works as expected eg. when converting or removing devices.
The only difference is when raid0 on two devices gets one device
removed. Unpatched would silently create a single profile, while newly
it would be raid0.
The motivation is to allow to preserve the profile type as long as it
possible for some intermediate state (device removal, conversion), or
when there are disks of different size, with raid0 the otherwise
unusable space of the last device will be used too. Similarly for
raid10, though the two largest devices would need to be the same.
Unpatched kernel will mount and use the degenerate profiles just fine
but won't allow any operation that would not satisfy the stricter device
number constraints, eg. not allowing to go from 3 to 2 devices for
raid10 or various profile conversions.
Example output:
# btrfs fi us -T .
Overall:
Device size: 10.00GiB
Device allocated: 1.01GiB
Device unallocated: 8.99GiB
Device missing: 0.00B
Used: 200.61MiB
Free (estimated): 9.79GiB (min: 9.79GiB)
Free (statfs, df): 9.79GiB
Data ratio: 1.00
Metadata ratio: 1.00
Global reserve: 3.25MiB (used: 0.00B)
Multiple profiles: no
Data Metadata System
Id Path RAID0 single single Unallocated
-- ---------- --------- --------- -------- -----------
1 /dev/sda10 1.00GiB 8.00MiB 1.00MiB 8.99GiB
-- ---------- --------- --------- -------- -----------
Total 1.00GiB 8.00MiB 1.00MiB 8.99GiB
Used 200.25MiB 352.00KiB 16.00KiB
Filipe Manana [Tue, 27 Jul 2021 10:24:45 +0000 (11:24 +0100)]
btrfs: do not pin logs too early during renames
During renames we pin the logs of the roots a bit too early, before the
calls to btrfs_insert_inode_ref(). We can pin the logs after those calls,
since those will not change anything in a log tree.
In a scenario where we have multiple and diverse filesystem operations
running in parallel, those calls can take a significant amount of time,
due to lock contention on extent buffers, and delay log commits from other
tasks for longer than necessary.
So just pin logs after calls to btrfs_insert_inode_ref() and right before
the first operation that can update a log tree.
The following script that uses dbench was used for testing:
$ cat dbench-test.sh
#!/bin/bash
DEV=/dev/nvme0n1
MNT=/mnt/nvme0n1
MOUNT_OPTIONS="-o ssd"
MKFS_OPTIONS="-m single -d single"
echo "performance" | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
Filipe Manana [Tue, 27 Jul 2021 10:24:44 +0000 (11:24 +0100)]
btrfs: eliminate some false positives when checking if inode was logged
When checking if an inode was previously logged in the current transaction
through the helper inode_logged(), we can return some false positives that
can be easily eliminated. These correspond to the cases where an inode has
a ->logged_trans value that is not zero and its value is smaller then the
ID of the current transaction. This means we know exactly that the inode
was never logged before in the current transaction, so we can return false
and avoid the callers to do extra work:
1) Having btrfs_del_dir_entries_in_log() and btrfs_del_inode_ref_in_log()
unnecessarily join a log transaction and do deletion searches in a log
tree that will not find anything. This just adds unnecessary contention
on extent buffer locks;
2) Having btrfs_log_new_name() unnecessarily log an inode when it is not
needed. If the inode was not logged before, we don't need to log it in
LOG_INODE_EXISTS mode.
So just make sure that any false positive only happens when ->logged_trans
has a value of 0.
Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: drop unnecessary ASSERT from btrfs_submit_direct()
When on SINGLE block group, btrfs_get_io_geometry() will return "the
size of the block group - the offset of the logical address within the
block group" as geom.len. Since we allow up to 8 GiB zone size on zoned
filesystem, we can have up to 8 GiB block group, so can have up to 8 GiB
geom.len as well. With this setup, we easily hit the "ASSERT(geom.len <=
INT_MAX);".
The ASSERT looks like to guard btrfs_bio_clone_partial() and bio_trim()
which both take "int" (now u64 due to the previous patch). So to be
precise the ASSERT should check if clone_len <= UINT_MAX. But actually,
clone_len is already capped by bio.bi_iter.bi_size which is unsigned
int. So the ASSERT is not necessary.
Drop the ASSERT and properly compare submit_len and geom.len in u64.
Then, let the implicit casting to convert it to u64.
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
The function bio_trim has offset and size arguments that are declared
as int.
The callers of this function use sector_t type when passing the offset
and size, e.g. drivers/md/raid1.c:narrow_write_error() and
drivers/md/raid1.c:narrow_write_error().
Change offset and size arguments to sector_t type for bio_trim(). Also,
add WARN_ON_ONCE() to catch their overflow.
Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 14 Jul 2021 18:47:25 +0000 (14:47 -0400)]
fs: kill sync_inode
Now that all users of sync_inode() have been deleted, remove
sync_inode().
Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 14 Jul 2021 18:47:24 +0000 (14:47 -0400)]
9p: migrate from sync_inode to filemap_fdatawrite_wbc
We're going to remove sync_inode, so migrate to filemap_fdatawrite_wbc
instead.
Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 14 Jul 2021 18:47:23 +0000 (14:47 -0400)]
btrfs: use the filemap_fdatawrite_wbc helper for delalloc shrinking
sync_inode() has some holes that can cause problems if we're under heavy
ENOSPC pressure. If there's writeback running on a separate thread
sync_inode() will skip writing the inode altogether. What we really
want is to make sure writeback has been started on all the pages to make
sure we can see the ordered extents and wait on them if appropriate.
Switch to this new helper which will allow us to accomplish this and
avoid ENOSPC'ing early.
Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 14 Jul 2021 18:47:22 +0000 (14:47 -0400)]
fs: add a filemap_fdatawrite_wbc helper
Btrfs sometimes needs to flush dirty pages on a bunch of dirty inodes in
order to reclaim metadata reservations. Unfortunately most helpers in
this area are too smart for us:
1) The normal filemap_fdata* helpers only take range and sync modes, and
don't give any indication of how much was written, so we can only
flush full inodes, which isn't what we want in most cases.
2) The normal writeback path requires us to have the s_umount sem held,
but we can't unconditionally take it in this path because we could
deadlock.
3) The normal writeback path also skips inodes with I_SYNC set if we
write with WB_SYNC_NONE. This isn't the behavior we want under heavy
ENOSPC pressure, we want to actually make sure the pages are under
writeback before returning, and if another thread is in the middle of
writing the file we may return before they're under writeback and
miss our ordered extents and not properly wait for completion.
4) sync_inode() uses the normal writeback path and has the same problem
as #3.
What we really want is to call do_writepages() with our wbc. This way
we can make sure that writeback is actually started on the pages, and we
can control how many pages are written as a whole as we write many
inodes using the same wbc. Accomplish this with a new helper that does
just that so we can use it for our ENOSPC flushing infrastructure.
Reviewed-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 14 Jul 2021 18:47:21 +0000 (14:47 -0400)]
btrfs: wait on async extents when flushing delalloc
I've been debugging an early ENOSPC problem in production and finally
root caused it to this problem. When we switched to the per-inode in cd75b8cc2e33 ("btrfs: use btrfs_start_delalloc_roots in
shrink_delalloc") I pulled out the async extent handling, because we
were doing the correct thing by calling filemap_flush() if we had async
extents set. This would properly wait on any async extents by locking
the page in the second flush, thus making sure our ordered extents were
properly set up.
However when I switched us back to page based flushing, I used
sync_inode(), which allows us to pass in our own wbc. The problem here
is that sync_inode() is smarter than the filemap_* helpers, it tries to
avoid calling writepages at all. This means that our second call could
skip calling do_writepages altogether, and thus not wait on the pagelock
for the async helpers. This means we could come back before any ordered
extents were created and then simply continue on in our flushing
mechanisms and ENOSPC out when we have plenty of space to use.
Fix this by putting back the async pages logic in shrink_delalloc. This
allows us to bulk write out everything that we need to, and then we can
wait in one place for the async helpers to catch up, and then wait on
any ordered extents that are created.
Fixes: de22c5b57c90 ("btrfs: shrink delalloc pages instead of full inodes") CC: stable@vger.kernel.org # 5.10+ Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 14 Jul 2021 18:47:20 +0000 (14:47 -0400)]
btrfs: use delalloc_bytes to determine flush amount for shrink_delalloc
We have been hitting some early ENOSPC issues in production with more
recent kernels, and I tracked it down to us simply not flushing delalloc
as aggressively as we should be. With tracing I was seeing us failing
all tickets with all of the block rsvs at or around 0, with very little
pinned space, but still around 120MiB of outstanding bytes_may_used.
Upon further investigation I saw that we were flushing around 14 pages
per shrink call for delalloc, despite having around 2GiB of delalloc
outstanding.
Consider the example of a 8 way machine, all CPUs trying to create a
file in parallel, which at the time of this commit requires 5 items to
do. Assuming a 16k leaf size, we have 10MiB of total metadata reclaim
size waiting on reservations. Now assume we have 128MiB of delalloc
outstanding. With our current math we would set items to 20, and then
set to_reclaim to 20 * 256k, or 5MiB.
Assuming that we went through this loop all 3 times, for both
FLUSH_DELALLOC and FLUSH_DELALLOC_WAIT, and then did the full loop
twice, we'd only flush 60MiB of the 128MiB delalloc space. This could
leave a fair bit of delalloc reservations still hanging around by the
time we go to ENOSPC out all the remaining tickets.
Fix this two ways. First, change the calculations to be a fraction of
the total delalloc bytes on the system. Prior to this change we were
calculating based on dirty inodes so our math made more sense, now it's
just completely unrelated to what we're actually doing.
Second add a FLUSH_DELALLOC_FULL state, that we hold off until we've
gone through the flush states at least once. This will empty the system
of all delalloc so we're sure to be truly out of space when we start
failing tickets.
I'm tagging stable 5.10 and forward, because this is where we started
using the page stuff heavily again. This affects earlier kernel
versions as well, but would be a pain to backport to them as the
flushing mechanisms aren't the same.
CC: stable@vger.kernel.org # 5.10+ Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 14 Jul 2021 18:47:19 +0000 (14:47 -0400)]
btrfs: enable a tracepoint when we fail tickets
When debugging early enospc problems it was useful to have a tracepoint
where we failed all tickets so I could check the state of the enospc
counters at failure time to validate my fixes. This adds the tracpoint
so you can easily get that information.
Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 14 Jul 2021 18:47:18 +0000 (14:47 -0400)]
btrfs: include delalloc related info in dump space info tracepoint
In order to debug delalloc flushing issues I added delalloc_bytes and
ordered_bytes to this tracepoint to see if they were non-zero when we
were going ENOSPC. This was valuable for me and showed me cases where we
weren't waiting on ordered extents properly. In order to add this to the
tracepoint we need to take away the const modifier for fs_info, as
percpu_sum_counter_positive() will change the counter when it adds up
the percpu buckets. This is needed to make sure we're getting accurate
information at these tracepoints, as the wrong information could send us
down the wrong path when debugging problems.
Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Josef Bacik [Wed, 14 Jul 2021 18:47:17 +0000 (14:47 -0400)]
btrfs: wake up async_delalloc_pages waiters after submit
We use the async_delalloc_pages mechanism to make sure that we've
completed our async work before trying to continue our delalloc
flushing. The reason for this is we need to see any ordered extents
that were created by our delalloc flushing. However we're waking up
before we do the submit work, which is before we create the ordered
extents. This is a pretty wide race window where we could potentially
think there are no ordered extents and thus exit shrink_delalloc
prematurely. Fix this by waking us up after we've done the work to
create ordered extents.
CC: stable@vger.kernel.org # 5.4+ Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com>
[CAUSE]
For subpage case, we can have multiple sectors inside a page, this makes
it possible for __extent_writepage() to have part of its page submitted
before returning.
In btrfs/160, we are using dm-dust to emulate write error, this means
for certain pages, we could have everything running fine, but at the end
of __extent_writepage(), one of the submitted bios fails due to dm-dust.
Then the page is marked Error, and we change @ret from 0 to -EIO.
This makes the caller extent_write_cache_pages() to error out, without
submitting the remaining pages.
Furthermore, since we're erroring out for free space cache, it doesn't
really care about the error and will update the inode and retry the
writeback.
Then we re-run the delalloc range, and will try to insert the same
delalloc range while previous delalloc range is still hanging there,
triggering the above error.
[FIX]
The proper fix is to handle errors from __extent_writepage() properly,
by ending the remaining ordered extent.
But that fix needs the following changes:
- Know at exactly which sector the error happened
Currently __extent_writepage_io() works for the full page, can't
return at which sector we hit the error.
- Grab the ordered extent covering the failed sector
As a hotfix for subpage case, here we unify the error paths in
__extent_writepage().
In fact, the "if (PageError(page))" branch never get executed if @ret is
still 0 for non-subpage cases.
As for non-subpage case, we never submit current page in
__extent_writepage(), but only add current page into bio.
The bio can only get submitted in next page.
Thus we never get PageError() set due to IO failure, thus when we hit
the branch, @ret is never 0.
By simply removing that @ret assignment, we let subpage case ignore the
IO failure, thus only error out for fatal errors just like regular
sectorsize.
So that IO error won't be treated as fatal error not trigger the hanging
OE problem.
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: allow read-write for 4K sectorsize on 64K page size systems
Since now we support data and metadata read-write for subpage, remove
the RO requirement for subpage mount.
There are some extra limitations though:
- For now, subpage RW mount is still considered experimental
Thus that mount warning will still be there.
- No compression support
There are still quite some PAGE_SIZE hard coded and quite some call
sites use extent_clear_unlock_delalloc() to unlock locked_page.
This will screw up subpage helpers.
Now for subpage RW mount, no matter what mount option or inode attr is
set, all writes will not be compressed. Although reading compressed
data has no problem.
- No defrag for subpage case
The defrag support for subpage case will come in later patches, which
will also rework the defrag workflow.
- No inline extent will be created
This is mostly due to the fact that filemap_fdatawrite_range() will
trigger more write than the range specified.
In fallocate calls, this behavior can make us to writeback which can
be inlined, before we enlarge the i_size.
This is a very special corner case, and even current btrfs check won't
report error on such inline extent + regular extent.
But considering how much effort has been put to prevent such inline +
regular, I'd prefer to cut off inline extent completely until we have
a good solution.
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Similar problem can be easily observed in btrfs/028 test case, there
will be tons of balance failure with -EIO.
[CAUSE]
Above fsstress will result the following data extents layout in extent
tree:
item 10 key (13631488 EXTENT_ITEM 98304) itemoff 15889 itemsize 82
refs 2 gen 7 flags DATA
extent data backref root FS_TREE objectid 259 offset 1339392 count 1
extent data backref root FS_TREE objectid 259 offset 647168 count 1
item 11 key (13631488 BLOCK_GROUP_ITEM 8388608) itemoff 15865 itemsize 24
block group used 102400 chunk_objectid 256 flags DATA
item 12 key (13733888 EXTENT_ITEM 4096) itemoff 15812 itemsize 53
refs 1 gen 7 flags DATA
extent data backref root FS_TREE objectid 259 offset 729088 count 1
Then when creating the data reloc inode, the data reloc inode will look
like this:
0 32K 64K 96K 100K 104K
|<------ Extent A ----->| |<- Ext B ->|
Then when we first try to relocate extent A, we setup the data reloc
inode with i_size 96K, then read both page [0, 64K) and page [64K, 128K).
For page 64K, since the i_size is just 96K, we fill range [96K, 128K)
with 0 and set it uptodate.
Then when we come to extent B, we update i_size to 104K, then try to read
page [64K, 128K).
Then we find the page is already uptodate, so we skip the read.
But range [96K, 128K) is filled with 0, not the real data.
Then we writeback the data reloc inode to disk, with 0 filling range
[96K, 128K), corrupting the content of extent B.
The behavior is caused by the fact that we still do full page read for
subpage case.
The bug won't really happen for regular sectorsize, as one page only
contains one sector.
[FIX]
This patch will fix the problem by invalidating range [i_size, PAGE_END]
in prealloc_file_extent_cluster().
So that if above example happens, when we preallocate the file extent
for extent B, we will clear the uptodate bits for range [96K, 128K),
allowing later relocate_one_page() to re-read the needed range.
There is a special note for the invalidating part.
Since we're not calling real btrfs_invalidatepage(), but just clearing
the subpage and page uptodate bits, we can leave a page half dirty and
half out of date.
Reading such page can cause a deadlock, as we normally expect a dirty
page to be fully uptodate.
Thus here we flush and wait the data reloc inode before doing the hacked
invalidating. This won't cause extra overhead, as we're going to
writeback the data later anyway.
btrfs: subpage: fix false alert when relocating partial preallocated data extents
[BUG]
When relocating partial preallocated data extents (part of the
preallocated extent is written) for subpage, it can cause the following
false alert and make the relocation to fail:
BTRFS info (device dm-3): balance: start -d
BTRFS info (device dm-3): relocating block group 13631488 flags data
BTRFS warning (device dm-3): csum failed root -9 ino 257 off 4096 csum 0x98757625 expected csum 0x00000000 mirror 1
BTRFS error (device dm-3): bdev /dev/mapper/arm_nvme-test errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
BTRFS warning (device dm-3): csum failed root -9 ino 257 off 4096 csum 0x98757625 expected csum 0x00000000 mirror 1
BTRFS error (device dm-3): bdev /dev/mapper/arm_nvme-test errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
BTRFS info (device dm-3): balance: ended with status: -5
[CAUSE]
Function btrfs_verify_data_csum() checks if the full range has
EXTENT_NODATASUM bit for data reloc inode, if *all* bytes of the range
have EXTENT_NODATASUM bit, then it skip the range.
This works pretty well for regular sectorsize, as in that case
btrfs_verify_data_csum() is called for each sector, thus no problem at
all.
But for subpage case, btrfs_verify_data_csum() is called on each bvec,
which can contain several sectors, and since it checks *all* bytes for
EXTENT_NODATASUM bit, if we have some range with csum, then we will
continue checking all the sectors.
For the preallocated sectors, it doesn't have any csum, thus obviously
the csum won't match and cause the false alert.
[FIX]
Move the EXTENT_NODATASUM check into the main loop, so that we can check
each sector for EXTENT_NODATASUM bit for subpage case.
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
The race can also happen between writeback and btrfs_invalidatepage(),
although that would be much harder as btrfs_invalidatepage() has much
more work to do before the clear_page_extent_mapped() call.
[FIX]
Here we "wait" for the subapge spinlock to be released before we detach
subpage structure.
So this patch will introduce a new function, wait_subpage_spinlock(), to
do the "wait" by acquiring the spinlock and release it.
Since the caller has ensured the page is not dirty nor writeback, and
page is already locked, the only way to hold the subpage spinlock is
from endio function.
Thus we only need to acquire the spinlock to wait for any existing
holder.
[CAUSE]
Although prepare_pages() calls find_or_create_page(), which returns the
page locked, but in later prepare_uptodate_page() calls, we may call
btrfs_readpage() which will unlock the page before it returns.
This leaves a window where btrfs_releasepage() can sneak in and release
the page, clearing page->private and causing above ASSERT().
[FIX]
In prepare_uptodate_page(), we should not only check page->mapping, but
also PagePrivate() to ensure we are still holding the correct page which
has proper fs context setup.
Reported-by: Ritesh Harjani <riteshh@linux.ibm.com> Tested-by: Ritesh Harjani <riteshh@linux.ibm.com> Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: subpage: allow submit_extent_page() to do bio split
Current submit_extent_page() just checks if the current page range can
be fitted into current bio, and if not, submit then re-add.
But this behavior can't handle subpage case at all.
For subpage case, the problem is in the page size, 64K, which is also
the same size as stripe size.
This means, if we can't fit a full 64K into a bio, due to stripe limit,
then it won't fit into next bio without crossing stripe either.
The proper way to handle it is:
- Check how many bytes we can be put into current bio
- Put as many bytes as possible into current bio first
- Submit current bio
- Create a new bio
- Add the remaining bytes into the new bio
Refactor submit_extent_page() so that it does the above iteration.
The main loop inside submit_extent_page() will look like this:
cur = pg_offset;
while (cur < pg_offset + size) {
u32 offset = cur - pg_offset;
int added;
if (!bio_ctrl->bio) {
/* Allocate new bio if needed */
}
/* Add as many bytes into the bio */
added = btrfs_bio_add_page();
if (added < size - offset) {
/* The current bio is full, submit it */
}
cur += added;
}
Also, since we're doing new bio allocation deep inside the main loop,
extract that code into a new helper, alloc_new_bio().
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
item 9 key (257 INODE_REF 256) itemoff 15703 itemsize 14
index 2 namelen 4 name: file
item 10 key (257 EXTENT_DATA 0) itemoff 14975 itemsize 728
generation 7 type 0 (inline)
inline extent data size 707 ram_bytes 707 compression 0 (none)
item 11 key (257 EXTENT_DATA 4096) itemoff 14922 itemsize 53
generation 7 type 2 (prealloc)
prealloc data disk byte 102346752 nr 4096
prealloc data offset 0 nr 4096
[CAUSE]
For subpage filesystem, the writeback is triggered in page units, which
means, even if we just want to writeback range [16K, 20K) for 64K page
system, we will still try to writeback any dirty sector of range [0, 64K).
This is never a problem if sectorsize == PAGE_SIZE, but for subpage,
this can cause unexpected problems.
For above test case, the last several operations from fsx are:
9055 trunc from 0x40000 to 0x2c3
9057 falloc from 0x164c to 0x19d2 (0x386 bytes)
In operation 9055, we dirtied sector [0, 4096), then in falloc, we call
btrfs_wait_ordered_range(inode, start=4096, len=4096), only expecting to
writeback any dirty data in [4096, 8192), but nothing else.
Unfortunately, in subpage case, above btrfs_wait_ordered_range() will
trigger writeback of the range [0, 64K), which includes the data at
[0, 4096).
And since at the call site, we haven't yet increased i_size, which is
still 707, this means cow_file_range() can insert an inline extent.
Resulting above inline + regular extent.
[WORKAROUND]
I don't really have any good short-term solution yet, as this means all
operations that would trigger writeback need to be reviewed for any
i_size change.
So here I choose to disable inline extent creation for subpage case as a
workaround. We have done tons of work just to avoid such extent, so I
don't to create an exception just for subpage.
This only affects inline extent creation, subpage has no problem reading
existing inline extents at all.
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
[CAUSE]
Above BUG_ON() means there is some bio range which doesn't have ordered
extent, which indeed is worth a BUG_ON().
Unlike regular sectorsize == PAGE_SIZE case, in subpage we have extra
subpage dirty bitmap to record which range is dirty and should be
written back.
This means, if we submit bio for a subpage range, we do not only need to
clear page dirty, but also need to clear subpage dirty bits.
In __extent_writepage_io(), we will call btrfs_page_clear_dirty() for
any range we submit a bio.
But there is loophole, if we hit a range which is beyond i_size, we just
call btrfs_writepage_endio_finish_ordered() to finish the ordered io,
then break out, without clearing the subpage dirty.
This means, if we hit above branch, the subpage dirty bits are still
there, if other range of the page get dirtied and we need to writeback
that page again, we will submit bio for the old range, leaving a wild
bio range which doesn't have ordered extent.
[FIX]
Fix it by always calling btrfs_page_clear_dirty() in
__extent_writepage_io().
Also to avoid such problem from happening again, add a new assert,
btrfs_page_assert_not_dirty(), to make sure both page dirty and subpage
dirty bits are cleared before exiting __extent_writepage_io().
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: make relocate_one_page() handle subpage case
For subpage case, one page of data reloc inode can contain several file
extents, like this:
|<--- File extent A --->| FE B | FE C |<--- File extent D -->|
|<--------- Page --------->|
We can no longer use PAGE_SIZE directly for various operations.
This patch will relocate_one_page() to handle subpage case by:
- Iterating through all extents of a cluster when marking pages
When marking pages dirty and delalloc, we need to check the cluster
extent boundary.
Now we introduce a loop to go extent by extent of a page, until we
either finished the last extent, or reach the page end.
By this, regular sectorsize == PAGE_SIZE can still work as usual, since
we will do that loop only once.
- Iteration start from max(page_start, extent_start)
Since we can have the following case:
| FE B | FE C |<--- File extent D -->|
|<--------- Page --------->|
Thus we can't always start from page_start, but do a
max(page_start, extent_start)
- Iteration end when the cluster is exhausted
Similar to previous case, the last file extent can end before the page
end:
|<--- File extent A --->| FE B | FE C |
|<--------- Page --------->|
In this case, we need to manually exit the loop after we have finished
the last extent of the cluster.
- Reserve metadata space for each extent range
Since now we can hit multiple ranges in one page, we should reserve
metadata for each range, not simply PAGE_SIZE.
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: rework lzo_decompress_bio() to make it subpage compatible
For the initial subpage support, although we won't support compressed
write, we still need to support compressed read.
But for lzo_decompress_bio() it has several problems:
- The abuse of PAGE_SIZE for boundary detection
For subpage case, we should follow sectorsize to detect the padding
zeros.
Using PAGE_SIZE will cause subpage compress read to skip certain
bytes, and causing read error.
- Too many helper variables
There are half a dozen helper variables, which is only making things
harder to read
This patch will rework lzo_decompress_bio() to make it work for subpage:
- Use sectorsize to do boundary check, while still use PAGE_SIZE for
page switching
This allows us to have the same on-disk format for 4K sectorsize fs,
while take advantage of larger page size.
- Use two main cursors
Only @cur_in and @cur_out is utilized as the main cursor.
The helper variables will only be declared inside the loop, and only 2
helper variables needed.
- Introduce a helper function to copy compressed segment payload
Introduce a new helper, copy_compressed_segment(), to copy a
compressed segment to workspace buffer.
This function will handle the page switching.
Now the net result is, with all the excessive comments and new helper
function, the refactored code is still smaller, and easier to read.
For other decompression code, they have no special padding rule, thus no
need to bother for initial subpage support, but will be refactored to
the same style later.
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
There are several bugs inside the function btrfs_decompress_buf2page()
- @start_byte doesn't take bvec.bv_offset into consideration
Thus it can't handle case where the target range is not page aligned.
- Too many helper variables
There are tons of helper variables, @buf_offset, @current_buf_start,
@start_byte, @prev_start_byte, @working_bytes, @bytes.
This hurts anyone who wants to read the function.
- No obvious main cursor for the iteartion
A new problem caused by previous problem.
- Comments for parameter list makes no sense
Like @buf_start is the offset to @buf, or offset inside the full
decompressed extent? (Spoiler alert, the later case)
And @total_out acts more like @buf_start + @size_of_buf.
The worst is @disk_start.
The real meaning of it is the file offset of the full decompressed
extent.
This patch will rework the whole function by:
- Add a proper comment with ASCII art to explain the parameter list
- Rework parameter list
The old @buf_start is renamed to @decompressed, to show how many bytes
are already decompressed inside the full decompressed extent.
The old @total_out is replaced by @buf_len, which is the decompressed
data size.
For old @disk_start and @bio, just pass @compressed_bio in.
- Use single main cursor
The main cursor will be @cur_file_offset, to show what's the current
file offset.
Other helper variables will be declared inside the main loop, and only
minimal amount of helper variables:
* offset_inside_decompressed_buf: The only real helper
* copy_start_file_offset: File offset we start memcpy
* bvec_file_offset: File offset of current bvec
Even with all these extensive comments, the final function is still
smaller than the original function, which is definitely a win.
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
For compressed read, we don't need to populate its io_bio->csum, as we
rely on compressed_bio->csum to verify the compressed data, and then
copy the decompressed to inode pages.
Normally btrfs_verify_data_csum() skip such page by checking and
clearing its PageChecked flag
But since that flag is still for the full page, when endio for inode
page range [0, 32K) gets executed, it clears PageChecked flag for the
full page.
Then when endio for inode page range [32K, 64K) gets executed, since the
page no longer has PageChecked flag, it just continues checking, even
though io_bio->csum is NULL.
[FIX]
Thankfully there are only two users of PageChecked bit:
- Cow fixup
Since subpage has its own way to trace page dirty (dirty_bitmap) and
ordered bit (ordered_bitmap), it should never trigger cow fixup.
- Compressed read
We can distinguish such read by just checking io_bio->csum.
So just check io_bio->csum before doing the verification to avoid such
NULL pointer dereference.
Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: reset this_bio_flag to avoid inheriting old flags
In btrfs_do_readpage(), we never reset @this_bio_flag after we hit a
compressed extent.
This is fine, as for PAGE_SIZE == sectorsize case, we can only have one
sector for one page, thus @this_bio_flag will only be set at most once.
But for subpage case, after hitting a compressed extent, @this_bio_flag
will always have EXTENT_BIO_COMPRESSED bit, even we're reading a regular
extent.
This will lead to various read errors, and causing new ASSERT() in
incoming subpage patches, which adds more strict check in
btrfs_submit_compressed_read().
Fix it by declaring @this_bio_flag inside the main loop and reset its
value for each iteration.
David Sterba [Mon, 26 Jul 2021 12:15:26 +0000 (14:15 +0200)]
btrfs: constify and cleanup variables in comparators
Comparators just read the data and thus get const parameters. This
should be also preserved by the local variables, update all comparators
passed to sort or bsearch.
Cleanups:
- unnecessary casts are dropped
- btrfs_cmp_device_free_bytes is cleaned up to follow the common pattern
and 'inline' is dropped as the function address is taken
David Sterba [Mon, 26 Jul 2021 12:15:24 +0000 (14:15 +0200)]
btrfs: simplify data stripe calculation helpers
There are two helpers doing the same calculations based on nparity and
ncopies. calc_data_stripes can be simplified into one expression, so far
we don't have profile with both copies and parity, so there's no
effective change. calc_stripe_length should reuse the helper and not
repeat the same calculation.
Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
David Sterba [Mon, 26 Jul 2021 12:15:19 +0000 (14:15 +0200)]
btrfs: uninline btrfs_bg_flags_to_raid_index
The helper does a simple translation from block group flags to index to
the btrfs_raid_array table. There's no apparent reason to inline the
function, the translation happens usually once per function and is not
called in a loop.
Making it a proper function saves quite some binary code (x86_64,
release config):
text data bss dec hex filename 1164011 19253 14912 1198176 124860 pre/btrfs.ko 1161559 19253 14912 1195724 123ecc post/btrfs.ko
DELTA: -2451
Also add the const attribute as there are no side effects, this could
help compiler to optimize a few things without the function body.
David Sterba [Mon, 26 Jul 2021 12:15:10 +0000 (14:15 +0200)]
btrfs: remove uptodate parameter from btrfs_dec_test_first_ordered_pending
In commit 7b29bb91d830 ("btrfs: refactor how we finish ordered extent io
for endio functions") there was last caller not using 1 for the uptodate
parameter. Now there's only one, passing 1, so we can remove it and
simplify the code.
Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: remove unused start and end parameters from btrfs_run_delalloc_range()
Since commit 9abe82629f47 ("btrfs: Remove
extent_io_ops::writepage_start_hook") removes the writepage_start_hook()
and adds btrfs_writepage_cow_fixup() function, there is no need to
follow the old hook parameters.
Remove the @start and @end hook, since currently the fixup check is full
page check, it doesn't need @start and @end hook.
Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs_search_slot is called in multiple places in dir-item.c to search
for a dir entry, and then calling btrfs_match_dir_name to return a
btrfs_dir_item.
In order to reduce the number of callers of btrfs_search_slot, create a
common function that looks for the dir key, and if found call
btrfs_match_dir_item_name.
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
btrfs: use btrfs_next_leaf instead of btrfs_next_item when slots > nritems
After calling btrfs_search_slot is a common practice to check if the
slot found isn't bigger than number of slots in the current leaf, and if
so, search for the same key in the next leaf by calling btrfs_next_leaf,
which calls btrfs_next_old_leaf to do the job.
Calling btrfs_next_item in the same situation would end up in the same
code flow, since
* btrfs_next_item
* btrfs_next_old_item
* if slot >= nritems(curr_leaf)
btrfs_next_old_leaf
Change btrfs_verify_dev_extents and calculate_emulated_zone_size
functions to use btrfs_next_leaf in the same situation.
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Thu, 22 Jul 2021 14:58:10 +0000 (15:58 +0100)]
btrfs: remove ignore_offset argument from btrfs_find_all_roots()
Currently all the callers of btrfs_find_all_roots() pass a value of false
for its ignore_offset argument. This makes the argument pointless and we
can remove it and make btrfs_find_all_roots() always pass false as the
ignore_offset argument for btrfs_find_all_roots_safe(). So just do that.
Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Tue, 20 Jul 2021 15:03:43 +0000 (16:03 +0100)]
btrfs: avoid unnecessary lock and leaf splits when updating inode in the log
During a fast fsync, if we have already fsynced the file before and in the
current transaction, we can make the inode item update more efficient and
avoid acquiring a write lock on the leaf's parent.
To update the inode item we are always using btrfs_insert_empty_item() to
get a path pointing to the inode item, which calls btrfs_search_slot()
with an "ins_len" argument of 'sizeof(struct btrfs_inode_item) +
sizeof(struct btrfs_item)', and that always results in the search taking
a write lock on the level 1 node that is the parent of the leaf that
contains the inode item. This adds unnecessary lock contention on log
trees when we have multiple fsyncs in parallel against inodes in the same
subvolume, which has a very significant impact due to the fact that log
trees are short lived and their height very rarely goes beyond level 2.
Also, by using btrfs_insert_empty_item() when we need to update the inode
item, we also end up splitting the leaf of the existing inode item when
the leaf has an amount of free space smaller than the size of an inode
item.
Improve this by using btrfs_seach_slot(), with a 0 "ins_len" argument,
when we know the inode item already exists in the log. This avoids these
two inefficiencies.
The following script, using fio, was used to perform the tests:
$ cat fio-test.sh
#!/bin/bash
DEV=/dev/nvme0n1
MNT=/mnt/nvme0n1
MOUNT_OPTIONS="-o ssd"
MKFS_OPTIONS="-d single -m single"
if [ $# -ne 4 ]; then
echo "Use $0 NUM_JOBS FILE_SIZE FSYNC_FREQ BLOCK_SIZE"
exit 1
fi
The tests were done on a physical machine, with 12 cores, 64G of RAM,
using a NVMEe device and using a non-debug kernel config (the default one
from Debian). The summary line from fio is provided below for each test
run.
With 8 jobs, file size 256M, fsync frequency of 4 and a block size of 4K:
The changes are small but it's possible to be better on faster hardware as
in the test machine used disk utilization was pretty much 100% during the
whole time the tests were running (observed with 'iostat -xz 1').
The tests also included the previous patch with the subject of:
"btrfs: avoid unnecessary log mutex contention when syncing log".
So they compared a branch without that patch and without this patch versus
a branch with these two patches applied.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Tue, 20 Jul 2021 15:03:42 +0000 (16:03 +0100)]
btrfs: remove unnecessary list head initialization when syncing log
One of the last steps of syncing the log is to remove all log contexts
from the root's list of contexts, done at btrfs_remove_all_log_ctxs().
There we iterate over all the contexts in the list and delete each one
from the list, and after that we call INIT_LIST_HEAD() on the list. That
is unnecessary since at that point the list is empty.
So just remove the INIT_LIST_HEAD() call. It's not needed, increases code
size (bloat-o-meter reported a delta of -122 for btrfs_sync_log() after
this change) and increases two critical sections delimited by log mutexes.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Tue, 20 Jul 2021 15:03:41 +0000 (16:03 +0100)]
btrfs: avoid unnecessary log mutex contention when syncing log
When syncing the log we acquire the root's log mutex just to update the
root's last_log_commit. This is unnecessary because:
1) At this point there can only be one task updating this value, which is
the task committing the current log transaction. Any task that enters
btrfs_sync_log() has to wait for the previous log transaction to commit
and wait for the current log transaction to commit if someone else
already started it (in this case it never reaches to the point of
updating last_log_commit, as that is done by the committing task);
2) All readers of the root's last_log_commit don't acquire the root's
log mutex. This is to avoid blocking the readers, potentially for too
long and because getting a stale value of last_log_commit does not
cause any functional problem, in the worst case getting a stale value
results in logging an inode unnecessarily. Plus it's actually very
rare to get a stale value that results in unnecessarily logging the
inode.
So in order to avoid unnecessary contention on the root's log mutex,
which is used for several different purposes, like starting/joining a
log transaction and starting writeback of a log transaction, stop
acquiring the log mutex for updating the root's last_log_commit.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Tue, 20 Jul 2021 15:03:40 +0000 (16:03 +0100)]
btrfs: remove racy and unnecessary inode transaction update when using no-holes
When using the NO_HOLES feature and expanding the size of an inode, we
update the inode's last_trans, last_sub_trans and last_log_commit fields
at maybe_insert_hole() so that a fsync does know that the inode needs to
be logged (by making sure that btrfs_inode_in_log() returns false). This
happens for expanding truncate operations, buffered writes, direct IO
writes and when cloning extents to an offset greater than the inode's
i_size.
However the way we do it is racy, because in between setting the inode's
last_sub_trans and last_log_commit fields, the log transaction ID that was
assigned to last_sub_trans might be committed before we read the root's
last_log_commit and assign that value to last_log_commit. If that happens
it would make a future call to btrfs_inode_in_log() return true. This is
a race that should be extremely unlikely to be hit in practice, and it is
the same that was described by commit 12d346d0823e0c ("btrfs: fix race
between marking inode needs to be logged and log syncing").
The fix would simply be to set last_log_commit to the value we assigned
to last_sub_trans minus 1, like it was done in that commit. However
updating these two fields plus the last_trans field is pointless here
because all the callers of btrfs_cont_expand() (which is the only
caller of maybe_insert_hole()) always call btrfs_set_inode_last_trans()
or btrfs_update_inode() after calling btrfs_cont_expand(). Calling either
btrfs_set_inode_last_trans() or btrfs_update_inode() guarantees that the
next fsync will log the inode, as it makes btrfs_inode_in_log() return
false.
So just remove the code that explicitly sets the inode's last_trans,
last_sub_trans and last_log_commit fields.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Tue, 20 Jul 2021 15:05:23 +0000 (16:05 +0100)]
btrfs: stop doing GFP_KERNEL memory allocations in the ref verify tool
In commit 1004c62b2e28e4 ("btrfs: use nofs allocations for running delayed
items") we wrapped all btree updates when running delayed items with
memalloc_nofs_save() and memalloc_nofs_restore(), due to a lock inversion
detected by lockdep involving reclaim and the mutex of delayed nodes.
The problem is because the ref verify tool does some memory allocations
with GFP_KERNEL, which can trigger reclaim and reclaim can trigger inode
eviction, which requires locking the mutex of an inode's delayed node.
On the other hand the ref verify tool is called when allocating metadata
extents as part of operations that modify a btree, which is a problem when
running delayed nodes, where we do btree updates while holding the mutex
of a delayed node. This is what caused the lockdep warning.
Instead of wrapping every btree update when running delayed nodes, change
the ref verify tool to never do GFP_KERNEL allocations, because:
1) We get less repeated code, which at the moment does not even have a
comment mentioning why we need to setup the NOFS context, which is a
recommended good practice as mentioned at
Documentation/core-api/gfp_mask-from-fs-io.rst
2) The ref verify tool is something meant only for debugging and not
something that should be enabled on non-debug / non-development
kernels;
3) We may have yet more places outside delayed-inode.c where we have
similar problem: doing btree updates while holding some lock and
then having the GFP_KERNEL memory allocations, from the ref verify
tool, trigger reclaim and trying again to acquire the same lock
through the reclaim path.
Or we could get more such cases in the future, therefore this change
prevents getting into similar cases when using the ref verify tool.
Curiously most of the memory allocations done by the ref verify tool
were already using GFP_NOFS, except a few ones for no apparent reason.
Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Filipe Manana [Tue, 20 Jul 2021 15:05:22 +0000 (16:05 +0100)]
btrfs: improve the batch insertion of delayed items
When we insert the delayed items of an inode, which corresponds to the
directory index keys for a directory (key type BTRFS_DIR_INDEX_KEY), we
do the following:
1) Pick the first delayed item from the rbtree and insert it into the
fs/subvolume btree, using btrfs_insert_empty_item() for that;
2) Without releasing the path returned by btrfs_insert_empty_item(),
keep collecting as many consecutive delayed items from the rbtree
as possible, as long as each one's BTRFS_DIR_INDEX_KEY key is the
immediate successor of the previously picked item and as long as
they fit in the available space of the leaf the path points to;
3) Then insert all the collected items into the leaf;
4) Release the reserve metadata space for each collected item and
release each item (implies deleting from the rbtree);
5) Unlock the path.
While this is much better than inserting items one by one, it can be
improved in a few aspects:
1) Instead of adding items based on the remaining free space of the
leaf, collect as many items that can fit in a leaf and bulk insert
them. This results in less and larger batches, reducing the total
amount of time to insert the delayed items. For example when adding
100K files to a directory, we ended up creating 1658 batches with
very variable sizes ranging from 1 item to 118 items, on a filesystem
with a node/leaf size of 16K. After this change, we end up with 839
batches, with the vast majority of them having exactly 120 items;
2) We do the search for more items to batch, by iterating the rbtree,
while holding a write lock on the leaf;
3) While still holding the leaf locked, we are releasing the reserved
metadata for each item and then deleting each item, keeping a write
lock on the leaf for longer than necessary. Releasing the delayed items
one by one can take a significant amount of time, because deleting
them from the rbtree can often be a bit slow when the deletion results
in rebalancing the rbtree.
So change this so that we try to create larger batches, with a total
item size up to the maximum a leaf can support, and by unlocking the leaf
immediately after inserting the items, releasing the reserved metadata
space of each item and releasing each item without holding the write lock
on the leaf.
The following script that runs fs_mark was used to test this change:
projects / kernel.git / log