linux-kernel - [PATCH 6.6.y 2/2] erofs: fix PSI memstall accounting

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Message-ID: <20250108151520.2515903-2-hsiangkao@linux.alibaba.com>
Date: Wed,  8 Jan 2025 23:15:20 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: stable@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-erofs@...ts.ozlabs.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 6.6.y 2/2] erofs: fix PSI memstall accounting

commit 1a2180f6859c73c674809f9f82e36c94084682ba upstream.

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@...os.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@...nel.org>
Link: https://lore.kernel.org/r/20241127085236.3538334-1-hsiangkao@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
---
 fs/erofs/zdata.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 9fa07436a4da..496e4c7c52a4 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -1730,11 +1730,10 @@ static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f,
 			move_to_bypass_jobqueue(pcl, qtail, owned_head);
 	} while (owned_head != Z_EROFS_PCLUSTER_TAIL);
 
-	if (bio) {
+	if (bio)
 		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.
-- 
2.43.5