Mikulas Patocka [Wed, 10 Feb 2021 20:26:23 +0000 (15:26 -0500)]
dm: fix deadlock when swapping to encrypted device
The system would deadlock when swapping to a dm-crypt device. The reason
is that for each incoming write bio, dm-crypt allocates memory that holds
encrypted data. These excessive allocations exhaust all the memory and the
result is either deadlock or OOM trigger.
This patch limits the number of in-flight swap bios, so that the memory
consumed by dm-crypt is limited. The limit is enforced if the target set
the "limit_swap_bios" variable and if the bio has REQ_SWAP set.
Non-swap bios are not affected becuase taking the semaphore would cause
performance degradation.
This is similar to request-based drivers - they will also block when the
number of requests is over the limit.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Satya Tangirala [Mon, 1 Feb 2021 05:10:18 +0000 (05:10 +0000)]
dm: support key eviction from keyslot managers of underlying devices
Now that device mapper supports inline encryption, add the ability to
evict keys from all underlying devices. When an upper layer requests
a key eviction, we simply iterate through all underlying devices
and evict that key from each device.
Co-developed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Satya Tangirala <satyat@google.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Satya Tangirala [Mon, 1 Feb 2021 05:10:17 +0000 (05:10 +0000)]
dm: add support for passing through inline crypto support
Update the device-mapper core to support exposing the inline crypto
support of the underlying device(s) through the device-mapper device.
This works by creating a "passthrough keyslot manager" for the dm
device, which declares support for encryption settings which all
underlying devices support. When a supported setting is used, the bio
cloning code handles cloning the crypto context to the bios for all the
underlying devices. When an unsupported setting is used, the blk-crypto
fallback is used as usual.
Crypto support on each underlying device is ignored unless the
corresponding dm target opts into exposing it. This is needed because
for inline crypto to semantically operate on the original bio, the data
must not be transformed by the dm target. Thus, targets like dm-linear
can expose crypto support of the underlying device, but targets like
dm-crypt can't. (dm-crypt could use inline crypto itself, though.)
A DM device's table can only be changed if the "new" inline encryption
capabilities are a (*not* necessarily strict) superset of the "old" inline
encryption capabilities. Attempts to make changes to the table that result
in some inline encryption capability becoming no longer supported will be
rejected.
For the sake of clarity, key eviction from underlying devices will be
handled in a future patch.
Co-developed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Satya Tangirala <satyat@google.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Satya Tangirala [Mon, 1 Feb 2021 05:10:16 +0000 (05:10 +0000)]
block/keyslot-manager: Introduce functions for device mapper support
Introduce blk_ksm_update_capabilities() to update the capabilities of
a keyslot manager (ksm) in-place. The pointer to a ksm in a device's
request queue may not be easily replaced, because upper layers like
the filesystem might access it (e.g. for programming keys/checking
capabilities) at the same time the device wants to replace that
request queue's ksm (and free the old ksm's memory). This function
allows the device to update the capabilities of the ksm in its request
queue directly. Devices can safely update the ksm this way without any
synchronization with upper layers *only* if the updated (new) ksm
continues to support all the crypto capabilities that the old ksm did
(see description below for blk_ksm_is_superset() for why this is so).
Also introduce blk_ksm_is_superset() which checks whether one ksm's
capabilities are a (not necessarily strict) superset of another ksm's.
The blk-crypto framework requires that crypto capabilities that were
advertised when a bio was created continue to be supported by the
device until that bio is ended - in practice this probably means that
a device's advertised crypto capabilities can *never* "shrink" (since
there's no synchronization between bio creation and when a device may
want to change its advertised capabilities) - so a previously
advertised crypto capability must always continue to be supported.
This function can be used to check that a new ksm is a valid
replacement for an old ksm.
Signed-off-by: Satya Tangirala <satyat@google.com> Reviewed-by: Eric Biggers <ebiggers@google.com> Acked-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The device mapper may map over devices that have inline encryption
capabilities, and to make use of those capabilities, the DM device must
itself advertise those inline encryption capabilities. One way to do this
would be to have the DM device set up a keyslot manager with a
"sufficiently large" number of keyslots, but that would use a lot of
memory. Also, the DM device itself has no "keyslots", and it doesn't make
much sense to talk about "programming a key into a DM device's keyslot
manager", so all that extra memory used to represent those keyslots is just
wasted. All a DM device really needs to be able to do is advertise the
crypto capabilities of the underlying devices in a coherent manner and
expose a way to evict keys from the underlying devices.
There are also devices with inline encryption hardware that do not
have a limited number of keyslots. One can send a raw encryption key along
with a bio to these devices (as opposed to typical inline encryption
hardware that require users to first program a raw encryption key into a
keyslot, and send the index of that keyslot along with the bio). These
devices also only need the same things from the keyslot manager that DM
devices need - a way to advertise crypto capabilities and potentially a way
to expose a function to evict keys from hardware.
So we introduce a "passthrough" keyslot manager that provides a way to
represent a keyslot manager that doesn't have just a limited number of
keyslots, and for which do not require keys to be programmed into keyslots.
DM devices can set up a passthrough keyslot manager in their request
queues, and advertise appropriate crypto capabilities based on those of the
underlying devices. Blk-crypto does not attempt to program keys into any
keyslots in the passthrough keyslot manager. Instead, if/when the bio is
resubmitted to the underlying device, blk-crypto will try to program the
key into the underlying device's keyslot manager.
Signed-off-by: Satya Tangirala <satyat@google.com> Reviewed-by: Eric Biggers <ebiggers@google.com> Acked-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Nikos Tsironis [Thu, 11 Feb 2021 14:22:43 +0000 (16:22 +0200)]
dm era: only resize metadata in preresume
Metadata resize shouldn't happen in the ctr. The ctr loads a temporary
(inactive) table that will only become active upon resume. That is why
resize should always be done in terms of resume. Otherwise a load (ctr)
whose inactive table never becomes active will incorrectly resize the
metadata.
Also, perform the resize directly in preresume, instead of using the
worker to do it.
The worker might run other metadata operations, e.g., it could start
digestion, before resizing the metadata. These operations will end up
using the old size.
Nikos Tsironis [Fri, 22 Jan 2021 15:25:53 +0000 (17:25 +0200)]
dm era: Verify the data block size hasn't changed
dm-era doesn't support changing the data block size of existing devices,
so check explicitly that the requested block size for a new target
matches the one stored in the metadata.
Nikos Tsironis [Fri, 22 Jan 2021 15:22:04 +0000 (17:22 +0200)]
dm era: Reinitialize bitset cache before digesting a new writeset
In case of devices with at most 64 blocks, the digestion of consecutive
eras uses the writeset of the first era as the writeset of all eras to
digest, leading to lost writes. That is, we lose the information about
what blocks were written during the affected eras.
The digestion code uses a dm_disk_bitset object to access the archived
writesets. This structure includes a one word (64-bit) cache to reduce
the number of array lookups.
This structure is initialized only once, in metadata_digest_start(),
when we kick off digestion.
But, when we insert a new writeset into the writeset tree, before the
digestion of the previous writeset is done, or equivalently when there
are multiple writesets in the writeset tree to digest, then all these
writesets are digested using the same cache and the cache is not
re-initialized when moving from one writeset to the next.
For devices with more than 64 blocks, i.e., the size of the cache, the
cache is indirectly invalidated when we move to a next set of blocks, so
we avoid the bug.
But for devices with at most 64 blocks we end up using the same cached
data for digesting all archived writesets, i.e., the cache is loaded
when digesting the first writeset and it never gets reloaded, until the
digestion is done.
As a result, the writeset of the first era to digest is used as the
writeset of all the following archived eras, leading to lost writes.
Fix this by reinitializing the dm_disk_bitset structure, and thus
invalidating the cache, every time the digestion code starts digesting a
new writeset.
Fixes: b83b01ee643a86 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Nikos Tsironis [Fri, 22 Jan 2021 15:19:31 +0000 (17:19 +0200)]
dm era: Update in-core bitset after committing the metadata
In case of a system crash, dm-era might fail to mark blocks as written
in its metadata, although the corresponding writes to these blocks were
passed down to the origin device and completed successfully.
Consider the following sequence of events:
1. We write to a block that has not been yet written in the current era
2. era_map() checks the in-core bitmap for the current era and sees
that the block is not marked as written.
3. The write is deferred for submission after the metadata have been
updated and committed.
4. The worker thread processes the deferred write
(process_deferred_bios()) and marks the block as written in the
in-core bitmap, **before** committing the metadata.
5. The worker thread starts committing the metadata.
6. We do more writes that map to the same block as the write of step (1)
7. era_map() checks the in-core bitmap and sees that the block is marked
as written, **although the metadata have not been committed yet**.
8. These writes are passed down to the origin device immediately and the
device reports them as completed.
9. The system crashes, e.g., power failure, before the commit from step
(5) finishes.
When the system recovers and we query the dm-era target for the list of
written blocks it doesn't report the aforementioned block as written,
although the writes of step (6) completed successfully.
The issue is that era_map() decides whether to defer or not a write
based on non committed information. The root cause of the bug is that we
update the in-core bitmap, **before** committing the metadata.
Fix this by updating the in-core bitmap **after** successfully
committing the metadata.
Fixes: b83b01ee643a86 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Nikos Tsironis [Fri, 22 Jan 2021 15:19:30 +0000 (17:19 +0200)]
dm era: Recover committed writeset after crash
Following a system crash, dm-era fails to recover the committed writeset
for the current era, leading to lost writes. That is, we lose the
information about what blocks were written during the affected era.
dm-era assumes that the writeset of the current era is archived when the
device is suspended. So, when resuming the device, it just moves on to
the next era, ignoring the committed writeset.
This assumption holds when the device is properly shut down. But, when
the system crashes, the code that suspends the target never runs, so the
writeset for the current era is not archived.
There are three issues that cause the committed writeset to get lost:
1. dm-era doesn't load the committed writeset when opening the metadata
2. The code that resizes the metadata wipes the information about the
committed writeset (assuming it was loaded at step 1)
3. era_preresume() starts a new era, without taking into account that
the current era might not have been archived, due to a system crash.
To fix this:
1. Load the committed writeset when opening the metadata
2. Fix the code that resizes the metadata to make sure it doesn't wipe
the loaded writeset
3. Fix era_preresume() to check for a loaded writeset and archive it,
before starting a new era.
Fixes: b83b01ee643a86 ("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Since commit ab83f88fbf95 ("block, bdi: an active gendisk always has a
request_queue associated with it") the request_queue pointer returned
from bdev_get_queue() shall never be NULL.
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Jeffle Xu [Tue, 9 Feb 2021 03:46:38 +0000 (22:46 -0500)]
dm table: fix zoned iterate_devices based device capability checks
Fix dm_table_supports_zoned_model() and invert logic of both
iterate_devices_callout_fn so that all devices' zoned capabilities are
properly checked.
Add one more parameter to dm_table_any_dev_attr(), which is actually
used as the @data parameter of iterate_devices_callout_fn, so that
dm_table_matches_zone_sectors() can be replaced by
dm_table_any_dev_attr().
Jeffle Xu [Tue, 2 Feb 2021 03:35:28 +0000 (11:35 +0800)]
dm table: fix iterate_devices based device capability checks
According to the definition of dm_iterate_devices_fn:
* This function must iterate through each section of device used by the
* target until it encounters a non-zero return code, which it then returns.
* Returns zero if no callout returned non-zero.
For some target type (e.g. dm-stripe), one call of iterate_devices() may
iterate multiple underlying devices internally, in which case a non-zero
return code returned by iterate_devices_callout_fn will stop the iteration
in advance. No iterate_devices_callout_fn should return non-zero unless
device iteration should stop.
Rename dm_table_requires_stable_pages() to dm_table_any_dev_attr() and
elevate it for reuse to stop iterating (and return non-zero) on the
first device that causes iterate_devices_callout_fn to return non-zero.
Use dm_table_any_dev_attr() to properly iterate through devices.
Rename device_is_nonrot() to device_is_rotational() and invert logic
accordingly to fix improper disposition.
Fixes: 0af311677e21 ("dm table: clear add_random unless all devices have it set") Fixes: 9c9257971b9a ("dm table: propagate non rotational flag") Cc: stable@vger.kernel.org Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Mikulas Patocka [Thu, 4 Feb 2021 10:20:52 +0000 (05:20 -0500)]
dm writecache: return the exact table values that were set
LVM doesn't like it when the target returns different values from what
was set in the constructor. Fix dm-writecache so that the returned
table values are exactly the same as requested values.
Ahmad Fatoum [Fri, 22 Jan 2021 08:43:20 +0000 (09:43 +0100)]
dm crypt: replaced #if defined with IS_ENABLED
IS_ENABLED(CONFIG_ENCRYPTED_KEYS) is true whether the option is built-in
or a module, so use it instead of #if defined checking for each
separately.
The other #if was to avoid a static function defined, but unused
warning. As we now always build the callsite when the function
is defined, we can remove that first #if guard.
Suggested-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de> Acked-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Remove NULL checks before vfree() to fix these warnings:
./drivers/md/dm-writecache.c:2008:2-7: WARNING: NULL check before some
freeing functions is not needed.
./drivers/md/dm-writecache.c:2024:2-7: WARNING: NULL check before some
freeing functions is not needed.
Signed-off-by: Tian Tao <tiantao6@hisilicon.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Mikulas Patocka [Thu, 21 Jan 2021 15:09:32 +0000 (10:09 -0500)]
dm integrity: introduce the "fix_hmac" argument
The "fix_hmac" argument improves security of internal_hash and
journal_mac:
- the section number is mixed to the mac, so that an attacker can't
copy sectors from one journal section to another journal section
- the superblock is protected by journal_mac
- a 16-byte salt stored in the superblock is mixed to the mac, so
that the attacker can't detect that two disks have the same hmac
key and also to disallow the attacker to move sectors from one
disk to another
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Reported-by: Daniel Glockner <dg@emlix.com> Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com> # ReST fix Tested-by: Milan Broz <gmazyland@gmail.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Jinoh Kang [Sun, 17 Jan 2021 11:49:33 +0000 (11:49 +0000)]
dm persistent data: fix return type of shadow_root()
shadow_root() truncates 64-bit dm_block_t into 32-bit int. This is
not an issue in practice, since dm metadata as of v5.11 can only hold at
most 4161600 blocks (255 index entries * ~16k metadata blocks).
Nevertheless, this can confuse users debugging some specific data
corruption scenarios. Also, DM_SM_METADATA_MAX_BLOCKS may be bumped in
the future, or persistent-data may find its use in other places.
Therefore, switch the return type of shadow_root from int to dm_block_t.
Signed-off-by: Jinoh Kang <jinoh.kang.kr@gmail.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Ming Lei [Tue, 2 Feb 2021 15:54:10 +0000 (23:54 +0800)]
block: fix memory leak of bvec
bio_init() clears bio instance, so the bvec index has to be set after
bio_init(), otherwise bio->bi_io_vec may be leaked.
Fixes: c41485517608 ("block: split bio_kmalloc from bio_alloc_bioset") Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com> Cc: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Cc: Damien Le Moal <damien.lemoal@wdc.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Lukas Bulwahn [Fri, 29 Jan 2021 05:01:51 +0000 (06:01 +0100)]
block: drop removed argument from kernel-doc of blk_execute_rq()
Commit 23a0599cbecb ("block: remove unnecessary argument from
blk_execute_rq") changes the signature of blk_execute_rq(), but misses
to adjust its kernel-doc.
Hence, make htmldocs warns on ./block/blk-exec.c:78:
warning: Excess function parameter 'q' description in 'blk_execute_rq'
Drop removed argument from kernel-doc of blk_execute_rq() as well.
Lukas Bulwahn [Fri, 29 Jan 2021 04:55:05 +0000 (05:55 +0100)]
block: remove typo in kernel-doc of set_disk_ro()
Commit e8a029c25bb9 ("block: add a hard-readonly flag to struct gendisk")
provides some kernel-doc for set_disk_ro(), but introduces a small typo.
Hence, make htmldocs warns on ./block/genhd.c:1441:
warning: Function parameter or member 'read_only' not described in 'set_disk_ro'
warning: Excess function parameter 'ready_only' description in 'set_disk_ro'
Remove that typo in the kernel-doc for set_disk_ro().
The commit 85774780ef96 ("block: store a block_device pointer in struct bio")
now uses bdev unconditionally in the macro bio_set_dev() and assumes
that bdev value is not NULL which results in the following crash in
since thats where bdev is actually accessed :-
void bio_associate_blkg_from_css(struct bio *bio,
struct cgroup_subsys_state *css)
{
if (bio->bi_blkg)
blkg_put(bio->bi_blkg);
Jens Axboe [Wed, 27 Jan 2021 17:04:49 +0000 (10:04 -0700)]
mm: only make map_swap_entry available for CONFIG_HIBERNATION
Current tree spews this on compile:
mm/swapfile.c:2290:17: warning: ‘map_swap_entry’ defined but not used [-Wunused-function]
2290 | static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
| ^~~~~~~~~~~~~~
if !CONFIG_HIBERNATION, as we don't use the function unless we have that
config option set.
Just reuse the block_device and sector from the swap_info structure,
just as used by the SWP_SYNCHRONOUS path. Also remove the checks for
NULL returns from bio_alloc as that can't happen for sleeping
allocations.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Acked-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Refactor raid5_read_one_chunk so that all simple checks are done
before allocating the bio.
Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Song Liu <song@kernel.org> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Acked-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
md_bio_alloc_sync is never called with a NULL mddev, and ->sync_set is
initialized in md_run, so it always must be initialized as well. Just
open code the remaining call to bio_alloc_bioset.
Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Song Liu <song@kernel.org> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Acked-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use an on-stack bio and biovec for the single page synchronous I/O.
Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Song Liu <song@kernel.org> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Acked-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
bio_alloc_mddev is never called with a NULL mddev, and ->bio_set is
initialized in md_run, so it always must be initialized as well. Just
open code the remaining call to bio_alloc_bioset.
Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Song Liu <song@kernel.org> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Acked-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Open code drbd_req_make_private_bio in the two callers to prepare
for further changes. Also don't bother to initialize bi_next as the
bio code already does that that.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Acked-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Given that drbd_md_io_bio_set is initialized during module initialization
and the module fails to load if the initialization fails there is no need
to fall back to plain bio_alloc.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Acked-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk-crypto: use bio_kmalloc in blk_crypto_clone_bio
Use bio_kmalloc instead of open coding it.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Acked-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Acked-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Jan Kara [Fri, 5 Jun 2020 14:16:18 +0000 (16:16 +0200)]
bfq: Use only idle IO periods for think time calculations
Currently whenever bfq queue has a request queued we add now -
last_completion_time to the think time statistics. This is however
misleading in case the process is able to submit several requests in
parallel because e.g. if the queue has request completed at time T0 and
then queues new requests at times T1, T2, then we will add T1-T0 and
T2-T0 to think time statistics which just doesn't make any sence (the
queue's think time is penalized by the queue being able to submit more
IO). So add to think time statistics only time intervals when the queue
had no IO pending.
Signed-off-by: Jan Kara <jack@suse.cz> Acked-by: Paolo Valente <paolo.valente@linaro.org>
[axboe: fix whitespace on empty line] Signed-off-by: Jens Axboe <axboe@kernel.dk>
Jan Kara [Fri, 5 Jun 2020 14:16:16 +0000 (16:16 +0200)]
bfq: Avoid false bfq queue merging
bfq_setup_cooperator() uses bfqd->in_serv_last_pos so detect whether it
makes sense to merge current bfq queue with the in-service queue.
However if the in-service queue is freshly scheduled and didn't dispatch
any requests yet, bfqd->in_serv_last_pos is stale and contains value
from the previously scheduled bfq queue which can thus result in a bogus
decision that the two queues should be merged. This bug can be observed
for example with the following fio jobfile:
where the 4 processes will end up in the one shared bfq queue although
they do IO to physically very distant files (for some reason I was able to
observe this only with slice_idle=1ms setting).
Fix the problem by invalidating bfqd->in_serv_last_pos when switching
in-service queue.
Fixes: 68db94066a5b ("block, bfq: fix in-service-queue check for queue merging") CC: stable@vger.kernel.org Signed-off-by: Jan Kara <jack@suse.cz> Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Jan Kara [Thu, 7 Jan 2021 15:40:34 +0000 (16:40 +0100)]
bdev: Do not return EBUSY if bdev discard races with write
blkdev_fallocate() tries to detect whether a discard raced with an
overlapping write by calling invalidate_inode_pages2_range(). However
this check can give both false negatives (when writing using direct IO
or when writeback already writes out the written pagecache range) and
false positives (when write is not actually overlapping but ends in the
same page when blocksize < pagesize). This actually causes issues for
qemu which is getting confused by EBUSY errors.
Fix the problem by removing this conflicting write detection since it is
inherently racy and thus of little use anyway.
Reported-by: Maxim Levitsky <mlevitsk@redhat.com> CC: "Darrick J. Wong" <darrick.wong@oracle.com> Link: https://lore.kernel.org/qemu-devel/20201111153913.41840-1-mlevitsk@redhat.com Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Cloned bios are can be used to on the same device, in which case we need
to inherit the BIO_REMAPPED flag to avoid a double partition remap. When
the cloned bios are used on another device, bio_set_dev will clear the flag.
Fixes: 85774780ef96 ("block: store a block_device pointer in struct bio") Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Paolo Valente [Mon, 25 Jan 2021 19:02:48 +0000 (20:02 +0100)]
block, bfq: make waker-queue detection more robust
In the presence of many parallel I/O flows, the detection of waker
bfq_queues suffers from false positives. This commits addresses this
issue by making the filtering of actual wakers more selective. In more
detail, a candidate waker must be found to meet waker requirements
three times before being promoted to actual waker.
Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Paolo Valente [Mon, 25 Jan 2021 19:02:47 +0000 (20:02 +0100)]
block, bfq: save also injection state on queue merging
To prevent injection information from being lost on bfq_queue merging,
also the amount of service that a bfq_queue receives must be saved and
restored when the bfq_queue is merged and split, respectively.
Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Paolo Valente [Mon, 25 Jan 2021 19:02:46 +0000 (20:02 +0100)]
block, bfq: save also weight-raised service on queue merging
To prevent weight-raising information from being lost on bfq_queue merging,
also the amount of service that a bfq_queue receives must be saved and
restored when the bfq_queue is merged and split, respectively.
Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Paolo Valente [Mon, 25 Jan 2021 19:02:45 +0000 (20:02 +0100)]
block, bfq: fix switch back from soft-rt weitgh-raising
A bfq_queue may happen to be deemed as soft real-time while it is
still enjoying interactive weight-raising. If this happens because of
a false positive, then the bfq_queue is likely to loose its soft
real-time status soon. Upon losing such a status, the bfq_queue must
get back its interactive weight-raising, if its interactive period is
not over yet. But this case is not handled. This commit corrects this
error.
Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Paolo Valente [Mon, 25 Jan 2021 19:02:44 +0000 (20:02 +0100)]
block, bfq: re-evaluate convenience of I/O plugging on rq arrivals
Upon an I/O-dispatch attempt, BFQ may detect that it was better to
plug I/O dispatch, and to wait for a new request to arrive for the
currently in-service queue. But the arrival of a new request for an
empty bfq_queue, and thus the switch from idle to busy of the
bfq_queue, may cause the scenario to change, and make plugging no
longer needed for service guarantees, or more convenient for
throughput. In this case, keeping I/O-dispatch plugged would certainly
lower throughput.
To address this issue, this commit makes such a check, and stops
plugging I/O if it is better to stop plugging I/O.
Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Paolo Valente [Mon, 25 Jan 2021 19:02:43 +0000 (20:02 +0100)]
block, bfq: replace mechanism for evaluating I/O intensity
Some BFQ mechanisms make their decisions on a bfq_queue basing also on
whether the bfq_queue is I/O bound. In this respect, the current logic
for evaluating whether a bfq_queue is I/O bound is rather rough. This
commits replaces this logic with a more effective one.
The new logic measures the percentage of time during which a bfq_queue
is active, and marks the bfq_queue as I/O bound if the latter if this
percentage is above a fixed threshold.
Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
block: skip bio_check_eod for partition-remapped bios
When an already remapped bio is resubmitted (e.g. by blk_queue_split),
bio_check_eod will compare the remapped bi_sector against the size
of the partition, leading to spurious I/O failures.
Skip the EOD check in this case.
Fixes: 85774780ef96 ("block: store a block_device pointer in struct bio") Reported-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pavel Begunkov [Sat, 9 Jan 2021 16:03:03 +0000 (16:03 +0000)]
bio: don't copy bvec for direct IO
The block layer spends quite a while in blkdev_direct_IO() to copy and
initialise bio's bvec. However, if we've already got a bvec in the input
iterator it might be reused in some cases, i.e. when new
ITER_BVEC_FLAG_FIXED flag is set. Simple tests show considerable
performance boost, and it also reduces memory footprint.
Suggested-by: Matthew Wilcox <willy@infradead.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pavel Begunkov [Sat, 9 Jan 2021 16:03:02 +0000 (16:03 +0000)]
bio: add a helper calculating nr segments to alloc
Add a helper function calculating the number of bvec segments we need to
allocate to construct a bio. It doesn't change anything functionally,
but will be used to not duplicate special cases in the future.
Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pavel Begunkov [Sat, 9 Jan 2021 16:03:01 +0000 (16:03 +0000)]
iov_iter: optimise bvec iov_iter_advance()
iov_iter_advance() is heavily used, but implemented through generic
means. For bvecs there is a specifically crafted function for that, so
use bvec_iter_advance() instead, it's faster and slimmer.
Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
target/file: allocate the bvec array as part of struct target_core_file_cmd
This saves one memory allocation, and ensures the bvecs aren't freed
before the AIO completion. This will allow the lower level code to be
optimized so that it can avoid allocating another bvec array.
Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pavel Begunkov [Sat, 9 Jan 2021 16:02:59 +0000 (16:02 +0000)]
block/psi: remove PSI annotations from direct IO
Direct IO does not operate on the current working set of pages managed
by the kernel, so it should not be accounted as memory stall to PSI
infrastructure.
The block layer and iomap direct IO use bio_iov_iter_get_pages()
to build bios, and they are the only users of it, so to avoid PSI
tracking for them clear out BIO_WORKINGSET flag. Do same for
dio_bio_submit() because fs/direct_io constructs bios by hand directly
calling bio_add_page().
Reported-by: Christoph Hellwig <hch@infradead.org> Suggested-by: Christoph Hellwig <hch@infradead.org> Suggested-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pavel Begunkov [Sat, 9 Jan 2021 16:02:58 +0000 (16:02 +0000)]
bvec/iter: disallow zero-length segment bvecs
zero-length bvec segments are allowed in general, but not handled by bio
and down the block layer so filtered out. This inconsistency may be
confusing and prevent from optimisations. As zero-length segments are
useless and places that were generating them are patched, declare them
not allowed.
Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pavel Begunkov [Sat, 9 Jan 2021 16:02:57 +0000 (16:02 +0000)]
splice: don't generate zero-len segement bvecs
iter_file_splice_write() may spawn bvec segments with zero-length. In
preparation for prohibiting them, filter out by hand at splice level.
Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Ming Lei [Mon, 11 Jan 2021 03:05:57 +0000 (11:05 +0800)]
bcache: don't pass BIOSET_NEED_BVECS for the 'bio_set' embedded in 'cache_set'
This bioset is just for allocating bio only from bio_next_split, and it
needn't bvecs, so remove the flag.
Cc: linux-bcache@vger.kernel.org Cc: Coly Li <colyli@suse.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Acked-by: Coly Li <colyli@suse.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Ming Lei [Mon, 11 Jan 2021 03:05:56 +0000 (11:05 +0800)]
block: move three bvec helpers declaration into private helper
bvec_alloc(), bvec_free() and bvec_nr_vecs() are only used inside block
layer core functions, no need to declare them in public header.
Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Ming Lei [Mon, 11 Jan 2021 03:05:55 +0000 (11:05 +0800)]
block: set .bi_max_vecs as actual allocated vector number
bvec_alloc() may allocate more bio vectors than requested, so set
.bi_max_vecs as actual allocated vector number, instead of the requested
number. This way can help fs build bigger bio because new bio often won't
be allocated until the current one becomes full.
Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Ming Lei [Mon, 11 Jan 2021 03:05:54 +0000 (11:05 +0800)]
block: don't allocate inline bvecs if this bioset needn't bvecs
The inline bvecs won't be used if user needn't bvecs by not passing
BIOSET_NEED_BVECS, so don't allocate bvecs in this situation.
Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Pavel Begunkov <asml.silence@gmail.com> Tested-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Ming Lei [Mon, 11 Jan 2021 03:05:53 +0000 (11:05 +0800)]
block: don't pass BIOSET_NEED_BVECS for q->bio_split
q->bio_split is only used by bio_split() for fast cloning bio, and no
need to allocate bvecs, so remove this flag.
Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Pavel Begunkov <asml.silence@gmail.com> Tested-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Ming Lei [Mon, 11 Jan 2021 03:05:52 +0000 (11:05 +0800)]
block: manage bio slab cache by xarray
Managing bio slab cache via xarray by using slab cache size as xarray
index, and storing 'struct bio_slab' instance into xarray.
So code is simplified a lot, meantime it becomes more readable than before.
Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Pavel Begunkov <asml.silence@gmail.com> Tested-by: Pavel Begunkov <asml.silence@gmail.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Jan Kara [Mon, 11 Jan 2021 16:47:17 +0000 (17:47 +0100)]
blk-mq: Improve performance of non-mq IO schedulers with multiple HW queues
Currently when non-mq aware IO scheduler (BFQ, mq-deadline) is used for
a queue with multiple HW queues, the performance it rather bad. The
problem is that these IO schedulers use queue-wide locking and their
dispatch function does not respect the hctx it is passed in and returns
any request it finds appropriate. Thus locality of request access is
broken and dispatch from multiple CPUs just contends on IO scheduler
locks. For these IO schedulers there's little point in dispatching from
multiple CPUs. Instead dispatch always only from a single CPU to limit
contention.
Below is a comparison of dbench runs on XFS filesystem where the storage
is a raid card with 64 HW queues and to it attached a single rotating
disk. BFQ is used as IO scheduler:
Numbers are times so lower is better. MQ is stock 5.10-rc6 kernel. SQ is
the same kernel with megaraid_sas.host_tagset_enable=0 so that the card
advertises just a single HW queue. MQ-Patched is a kernel with this
patch applied.
You can see multiple hardware queues heavily hurt performance in
combination with BFQ. The patch restores the performance.
Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Since both mq-deadline and BFQ completely ignore hctx they are passed to
their dispatch function and dispatch whatever request they deem fit
checking whether any request for a particular hctx is queued is just
pointless since we'll very likely get a request from a different hctx
anyway. In the following commit we'll deal with lock contention in these
IO schedulers in presence of multiple HW queues in a different way.
Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Paolo Valente [Fri, 22 Jan 2021 18:19:48 +0000 (19:19 +0100)]
block, bfq: do not expire a queue when it is the only busy one
This commits preserves I/O-dispatch plugging for a special symmetric
case that may suddenly turn into asymmetric: the case where only one
bfq_queue, say bfqq, is busy. In this case, not expiring bfqq does not
cause any harm to any other queues in terms of service guarantees. In
contrast, it avoids the following unlucky sequence of events: (1) bfqq
is expired, (2) a new queue with a lower weight than bfqq becomes busy
(or more queues), (3) the new queue is served until a new request
arrives for bfqq, (4) when bfqq is finally served, there are so many
requests of the new queue in the drive that the pending requests for
bfqq take a lot of time to be served. In particular, event (2) may
case even already dispatched requests of bfqq to be delayed, inside
the drive. So, to avoid this series of events, the scenario is
preventively declared as asymmetric also if bfqq is the only busy
queues. By doing so, I/O-dispatch plugging is performed for bfqq.
Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Paolo Valente [Fri, 22 Jan 2021 18:19:47 +0000 (19:19 +0100)]
block, bfq: avoid spurious switches to soft_rt of interactive queues
BFQ tags some bfq_queues as interactive or soft_rt if it deems that
these bfq_queues contain the I/O of, respectively, interactive or soft
real-time applications. BFQ privileges both these special types of
bfq_queues over normal bfq_queues. To privilege a bfq_queue, BFQ
mainly raises the weight of the bfq_queue. In particular, soft_rt
bfq_queues get a higher weight than interactive bfq_queues.
A bfq_queue may turn from interactive to soft_rt. And this leads to a
tricky issue. Soft real-time applications usually start with an
I/O-bound, interactive phase, in which they load themselves into main
memory. BFQ correctly detects this phase, and keeps the bfq_queues
associated with the application in interactive mode for a
while. Problems arise when the I/O pattern of the application finally
switches to soft real-time. One of the conditions for a bfq_queue to
be deemed as soft_rt is that the bfq_queue does not consume too much
bandwidth. But the bfq_queues associated with a soft real-time
application consume as much bandwidth as they can in the loading phase
of the application. So, after the application becomes truly soft
real-time, a lot of time should pass before the average bandwidth
consumed by its bfq_queues finally drops to a value acceptable for
soft_rt bfq_queues. As a consequence, there might be a time gap during
which the application is not privileged at all, because its bfq_queues
are not interactive any longer, but cannot be deemed as soft_rt yet.
To avoid this problem, BFQ pretends that an interactive bfq_queue
consumes zero bandwidth, and allows an interactive bfq_queue to switch
to soft_rt. Yet, this fake zero-bandwidth consumption easily causes
the bfq_queue to often switch to soft_rt deceptively, during its
loading phase. As in soft_rt mode, the bfq_queue gets its bandwidth
correctly computed, and therefore soon switches back to
interactive. Then it switches again to soft_rt, and so on. These
spurious fluctuations usually cause losses of throughput, because they
deceive BFQ's mechanisms for boosting throughput (injection,
I/O-plugging avoidance, ...).
This commit addresses this issue as follows:
1) It does compute actual bandwidth consumption also for interactive
bfq_queues. This avoids the above false positives.
2) When a bfq_queue switches from interactive to normal mode, the
consumed bandwidth is reset (forgotten). This allows the
bfq_queue to enjoy soft_rt very quickly. In particular, two
alternatives are possible in this switch:
- the bfq_queue still has backlog, and therefore there is a budget
already scheduled to serve the bfq_queue; in this case, the
scheduling of the current budget of the bfq_queue is not
hindered, because only the scheduling of the next budget will
be affected by the weight drop. After that, if the bfq_queue is
actually in a soft_rt phase, and becomes empty during the
service of its current budget, which is the natural behavior of
a soft_rt bfq_queue, then the bfq_queue will be considered as
soft_rt when its next I/O arrives. If, in contrast, the
bfq_queue remains constantly non-empty, then its next budget
will be scheduled with a low weight, which is the natural
treatment for an I/O-bound (non soft_rt) bfq_queue.
- the bfq_queue is empty; in this case, the bfq_queue may be
considered unjustly soft_rt when its new I/O arrives. Yet
the problem is now much smaller than before, because it is
unlikely that more than one spurious fluctuation occurs.
Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Paolo Valente [Fri, 22 Jan 2021 18:19:46 +0000 (19:19 +0100)]
block, bfq: do not raise non-default weights
BFQ heuristics try to detect interactive I/O, and raise the weight of
the queues containing such an I/O. Yet, if also the user changes the
weight of a queue (i.e., the user changes the ioprio of the process
associated with that queue), then it is most likely better to prevent
BFQ heuristics from silently changing the same weight.
Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Jia Cheng Hu [Fri, 22 Jan 2021 18:19:44 +0000 (19:19 +0100)]
block, bfq: set next_rq to waker_bfqq->next_rq in waker injection
Since commit c5089591c3ba ("block, bfq: detect wakers and
unconditionally inject their I/O"), when the in-service bfq_queue, say
Q, is temporarily empty, BFQ checks whether there are I/O requests to
inject (also) from the waker bfq_queue for Q. To this goal, the value
pointed by bfqq->waker_bfqq->next_rq must be controlled. However, the
current implementation mistakenly looks at bfqq->next_rq, which
instead points to the next request of the currently served queue.
This mistake evidently causes losses of throughput in scenarios with
waker bfq_queues.
This commit corrects this mistake.
Fixes: c5089591c3ba ("block, bfq: detect wakers and unconditionally inject their I/O") Signed-off-by: Jia Cheng Hu <jia.jiachenghu@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Paolo Valente [Fri, 22 Jan 2021 18:19:43 +0000 (19:19 +0100)]
block, bfq: use half slice_idle as a threshold to check short ttime
The value of the I/O plugging (idling) timeout is used also as the
think-time threshold to decide whether a process has a short think
time. In this respect, a good value of this timeout for rotational
drives is un the order of several ms. Yet, this is often too long a
time interval to be effective as a think-time threshold. This commit
mitigates this problem (by a lot, according to tests), by halving the
threshold.
Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that no fast path lookups in the partition table are left, there is
no point in micro-optimizing the data structure for it. Just use a bog
standard xarray.
projects / kernel.git / log