linux-ext4 - [PATCH 7/6] fs: improve comment in fserror_alloc

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Message-ID: <20260106233349.GL191501@frogsfrogsfrogs>
Date: Tue, 6 Jan 2026 15:33:49 -0800
From: "Darrick J. Wong" <djwong@...nel.org>
To: jack@...e.cz, brauner@...nel.org
Cc: linux-api@...r.kernel.org, hch@....de, linux-ext4@...r.kernel.org,
	linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	gabriel@...sman.be, amir73il@...il.com
Subject: [PATCH 7/6] fs: improve comment in fserror_alloc_event

From: Darrick J. Wong <djwong@...nel.org>

Document the ordering requirements between SB_ACTIVE and
s_pending_errors in the new fserror code.

Cc: jack@...e.cz
Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
 fs/fserror.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/fserror.c b/fs/fserror.c
index ec92f5a6db59ce..06ca86adab9b76 100644
--- a/fs/fserror.c
+++ b/fs/fserror.c
@@ -79,6 +79,11 @@ static inline struct fserror_event *fserror_alloc_event(struct super_block *sb,
 	 * If pending_errors already reached zero or is no longer active,
 	 * the superblock is being deactivated so there's no point in
 	 * continuing.
+	 *
+	 * The order of the check of s_pending_errors and SB_ACTIVE are
+	 * mandated by order of accesses in generic_shutdown_super and
+	 * fserror_unmount.  Barriers are implicitly provided by the refcount
+	 * manipulations in this function and fserror_unmount.
 	 */
 	if (!refcount_inc_not_zero(&sb->s_pending_errors))
 		return NULL;