From fd115d6fb30091c780bfcec24618b804601237aa Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 3 Jul 2022 22:35:56 -0400 Subject: [PATCH] step_into(): move fetching ->d_inode past handle_mounts() ... and lose messing with it in __follow_mount_rcu() Signed-off-by: Al Viro --- fs/namei.c | 31 +++++++++++-------------------- 1 file changed, 11 insertions(+), 20 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 3e30cec54ced7..ed3ffd9b22a36 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1474,8 +1474,7 @@ EXPORT_SYMBOL(follow_down); * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if * we meet a managed dentry that would need blocking. */ -static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, - struct inode **inode) +static bool __follow_mount_rcu(struct nameidata *nd, struct path *path) { struct dentry *dentry = path->dentry; unsigned int flags = dentry->d_flags; @@ -1505,13 +1504,6 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, dentry = path->dentry = mounted->mnt.mnt_root; nd->state |= ND_JUMPED; nd->next_seq = read_seqcount_begin(&dentry->d_seq); - *inode = dentry->d_inode; - /* - * We don't need to re-check ->d_seq after this - * ->d_inode read - there will be an RCU delay - * between mount hash removal and ->mnt_root - * becoming unpinned. - */ flags = dentry->d_flags; // makes sure that non-RCU pathwalk could reach // this state. @@ -1527,7 +1519,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, } static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, - struct path *path, struct inode **inode) + struct path *path) { bool jumped; int ret; @@ -1536,12 +1528,7 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, path->dentry = dentry; if (nd->flags & LOOKUP_RCU) { unsigned int seq = nd->next_seq; - *inode = dentry->d_inode; - if (read_seqcount_retry(&dentry->d_seq, seq)) - return -ECHILD; - if (unlikely(!*inode)) - return -ENOENT; - if (likely(__follow_mount_rcu(nd, path, inode))) + if (likely(__follow_mount_rcu(nd, path))) return 0; // *path and nd->next_seq might've been clobbered path->mnt = nd->path.mnt; @@ -1561,8 +1548,6 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, dput(path->dentry); if (path->mnt != nd->path.mnt) mntput(path->mnt); - } else { - *inode = d_backing_inode(path->dentry); } return ret; } @@ -1843,15 +1828,21 @@ static const char *step_into(struct nameidata *nd, int flags, { struct path path; struct inode *inode; - int err = handle_mounts(nd, dentry, &path, &inode); + int err = handle_mounts(nd, dentry, &path); if (err < 0) return ERR_PTR(err); + inode = path.dentry->d_inode; if (likely(!d_is_symlink(path.dentry)) || ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) || (flags & WALK_NOFOLLOW)) { /* not a symlink or should not follow */ - if (!(nd->flags & LOOKUP_RCU)) { + if (nd->flags & LOOKUP_RCU) { + if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq)) + return ERR_PTR(-ECHILD); + if (unlikely(!inode)) + return ERR_PTR(-ENOENT); + } else { dput(nd->path.dentry); if (nd->path.mnt != path.mnt) mntput(nd->path.mnt); -- 2.39.5