4.17-stable review patch. If anyone has any objections, please let me know.
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From: Tejun Heo tj@kernel.org
commit 8a301eb16d99983a4961f884690ec97b92e7dcfe upstream.
If a connection gets aborted while congested, FUSE can leave nr_wb_congested[] stuck until reboot causing wait_iff_congested() to wait spuriously which can lead to severe performance degradation.
The leak is caused by gating congestion state clearing with fc->connected test in request_end(). This was added way back in 2009 by 26c3679101db ("fuse: destroy bdi on umount"). While the commit description doesn't explain why the test was added, it most likely was to avoid dereferencing bdi after it got destroyed.
Since then, bdi lifetime rules have changed many times and now we're always guaranteed to have access to the bdi while the superblock is alive (fc->sb).
Drop fc->connected conditional to avoid leaking congestion states.
Signed-off-by: Tejun Heo tj@kernel.org Reported-by: Joshua Miller joshmiller@fb.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: stable@vger.kernel.org # v2.6.29+ Acked-by: Jan Kara jack@suse.cz Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/fuse/dev.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
--- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -381,8 +381,7 @@ static void request_end(struct fuse_conn if (!fc->blocked && waitqueue_active(&fc->blocked_waitq)) wake_up(&fc->blocked_waitq);
- if (fc->num_background == fc->congestion_threshold && - fc->connected && fc->sb) { + if (fc->num_background == fc->congestion_threshold && fc->sb) { clear_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC); clear_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC); }