linux-ext4 - [PATCH] ext4: recheck buffer uptodate bit under buffer lock

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Date:   Fri, 10 Sep 2021 16:03:16 +0800
From:   Zhang Yi <yi.zhang@...wei.com>
To:     <linux-ext4@...r.kernel.org>
CC:     <tytso@....edu>, <adilger.kernel@...ger.ca>, <jack@...e.cz>,
        <yi.zhang@...wei.com>, <yukuai3@...wei.com>
Subject: [PATCH] ext4: recheck buffer uptodate bit under buffer lock

Commit 8e33fadf945a ("ext4: remove an unnecessary if statement in
__ext4_get_inode_loc()") forget to recheck buffer's uptodate bit again
under buffer lock, which may overwrite the buffer if someone else have
already brought it uptodate and changed it.

Fixes: 8e33fadf945a ("ext4: remove an unnecessary if statement in __ext4_get_inode_loc()")
Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
---
 fs/ext4/inode.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d18852d6029c..236adc647eb0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4340,6 +4340,12 @@ static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
 		goto has_buffer;
 
 	lock_buffer(bh);
+	if (ext4_buffer_uptodate(bh)) {
+		/* Someone brought it uptodate while we waited */
+		unlock_buffer(bh);
+		goto has_buffer;
+	}
+
 	/*
 	 * If we have all information of the inode in memory and this
 	 * is the only valid inode in the block, we need not read the
-- 
2.31.1