From: Eric Sandeen sandeen@redhat.com

mainline inclusion from mainline-v5.5-rc3 commit 1edc8eb2e93130e36ac74ac9c80913815a57d413 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IB3D4A CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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When a filesystem is unmounted, we currently call fsnotify_sb_delete() before evict_inodes(), which means that fsnotify_unmount_inodes() must iterate over all inodes on the superblock looking for any inodes with watches. This is inefficient and can lead to livelocks as it iterates over many unwatched inodes.

At this point, SB_ACTIVE is gone and dropping refcount to zero kicks the inode out out immediately, so anything processed by fsnotify_sb_delete / fsnotify_unmount_inodes gets evicted in that loop.

After that, the call to evict_inodes will evict everything else with a zero refcount.

This should speed things up overall, and avoid livelocks in fsnotify_unmount_inodes().

Signed-off-by: Eric Sandeen sandeen@redhat.com Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Al Viro viro@zeniv.linux.org.uk

Conflicts: fs/super.c [Simple context conflict, direct adaptation.] Signed-off-by: Zizhi Wo wozizhi@huawei.com --- fs/notify/fsnotify.c | 3 +++ fs/super.c | 4 +++- 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c index e8ee4263d7b2..48caa1af5301 100644 --- a/fs/notify/fsnotify.c +++ b/fs/notify/fsnotify.c @@ -70,6 +70,9 @@ void fsnotify_unmount_inodes(struct super_block *sb) * doing an __iget/iput with SB_ACTIVE clear would actually * evict all inodes with zero i_count from icache which is * unnecessarily violent and may in fact be illegal to do. + * However, we should have been called /after/ evict_inodes + * removed all zero refcount inodes, in any case. Test to + * be sure. */ if (!atomic_read(&inode->i_count)) { spin_unlock(&inode->i_lock); diff --git a/fs/super.c b/fs/super.c index 8dc26e23f1a3..a916bfe228dd 100644 --- a/fs/super.c +++ b/fs/super.c @@ -442,10 +442,12 @@ void generic_shutdown_super(struct super_block *sb) sync_filesystem(sb); sb->s_flags &= ~SB_ACTIVE;

- fsnotify_unmount_inodes(sb); cgroup_writeback_umount();

+ /* evict all inodes with zero refcount */ evict_inodes(sb); + /* only nonzero refcount inodes can have marks */ + fsnotify_unmount_inodes(sb);

if (sb->s_dio_done_wq) { destroy_workqueue(sb->s_dio_done_wq);