erofs: fix PSI memstall accounting

[ Upstream commit 1a2180f6859c73c674809f9f82e36c94084682ba ]

Max Kellermann recently reported psi_group_cpu.tasks[NR_MEMSTALL] is
incorrect in the 6.11.9 kernel.

The root cause appears to be that, since the problematic commit, bio
can be NULL, causing psi_memstall_leave() to be skipped in
z_erofs_submit_queue().

Reported-by: Max Kellermann <max.kellermann@ionos.com>
Closes: https://lore.kernel.org/r/CAKPOu+8tvSowiJADW2RuKyofL_CSkm_SuyZA7ME5vMLWmL6pqw@mail.gmail.com
Fixes: 9e2f9d34dd12 ("erofs: handle overlapped pclusters out of crafted images properly")
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20241127085236.3538334-1-hsiangkao@linux.alibaba.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index a569ff9dfd04424596e79b59c578b349fea07680..1a00f061798a3ca7055448797a62251e3df37a44 100644 (file)
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -1679,9 +1679,9 @@ drain_io:
                        erofs_fscache_submit_bio(bio);
                else
                        submit_bio(bio);
-               if (memstall)
-                       psi_memstall_leave(&pflags);
        }
+       if (memstall)
+               psi_memstall_leave(&pflags);
 
        /*
         * although background is preferred, no one is pending for submission.