linux-kernel - [PATCH AUTOSEL 5.15 13/17] ext4: fix warning when submitting superblock in ext4_commit

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Date:   Tue, 21 Jun 2022 16:50:36 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Zhang Yi <yi.zhang@...wei.com>, Hulk Robot <hulkci@...wei.com>,
        Jan Kara <jack@...e.cz>,
        Ritesh Harjani <ritesh.list@...il.com>,
        Theodore Ts'o <tytso@....edu>, Sasha Levin <sashal@...nel.org>,
        adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 13/17] ext4: fix warning when submitting superblock in ext4_commit_super()

From: Zhang Yi <yi.zhang@...wei.com>

[ Upstream commit 15baa7dcadf1c4f0b4f752dc054191855ff2d78e ]

We have already check the io_error and uptodate flag before submitting
the superblock buffer, and re-set the uptodate flag if it has been
failed to write out. But it was lockless and could be raced by another
ext4_commit_super(), and finally trigger '!uptodate' WARNING when
marking buffer dirty. Fix it by submit buffer directly.

Reported-by: Hulk Robot <hulkci@...wei.com>
Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
Reviewed-by: Jan Kara <jack@...e.cz>
Reviewed-by: Ritesh Harjani <ritesh.list@...il.com>
Link: https://lore.kernel.org/r/20220520023216.3065073-1-yi.zhang@huawei.com
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ext4/super.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 91b83749ee11..c5082f0ffcb4 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5479,7 +5479,6 @@ static void ext4_update_super(struct super_block *sb)
 static int ext4_commit_super(struct super_block *sb)
 {
 	struct buffer_head *sbh = EXT4_SB(sb)->s_sbh;
-	int error = 0;
 
 	if (!sbh)
 		return -EINVAL;
@@ -5488,6 +5487,13 @@ static int ext4_commit_super(struct super_block *sb)
 
 	ext4_update_super(sb);
 
+	lock_buffer(sbh);
+	/* Buffer got discarded which means block device got invalidated */
+	if (!buffer_mapped(sbh)) {
+		unlock_buffer(sbh);
+		return -EIO;
+	}
+
 	if (buffer_write_io_error(sbh) || !buffer_uptodate(sbh)) {
 		/*
 		 * Oh, dear.  A previous attempt to write the
@@ -5502,17 +5508,21 @@ static int ext4_commit_super(struct super_block *sb)
 		clear_buffer_write_io_error(sbh);
 		set_buffer_uptodate(sbh);
 	}
-	BUFFER_TRACE(sbh, "marking dirty");
-	mark_buffer_dirty(sbh);
-	error = __sync_dirty_buffer(sbh,
-		REQ_SYNC | (test_opt(sb, BARRIER) ? REQ_FUA : 0));
+	get_bh(sbh);
+	/* Clear potential dirty bit if it was journalled update */
+	clear_buffer_dirty(sbh);
+	sbh->b_end_io = end_buffer_write_sync;
+	submit_bh(REQ_OP_WRITE,
+		  REQ_SYNC | (test_opt(sb, BARRIER) ? REQ_FUA : 0), sbh);
+	wait_on_buffer(sbh);
 	if (buffer_write_io_error(sbh)) {
 		ext4_msg(sb, KERN_ERR, "I/O error while writing "
 		       "superblock");
 		clear_buffer_write_io_error(sbh);
 		set_buffer_uptodate(sbh);
+		return -EIO;
 	}
-	return error;
+	return 0;
 }
 
 /*
-- 
2.35.1