linux-ext4 - [PATCH 02/20] ext4: prevent partial update of the extents path

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Message-Id: <20240710040654.1714672-3-libaokun@huaweicloud.com>
Date: Wed, 10 Jul 2024 12:06:36 +0800
From: libaokun@...weicloud.com
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.cz,
	ritesh.list@...il.com,
	linux-kernel@...r.kernel.org,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	libaokun@...weicloud.com,
	Baokun Li <libaokun1@...wei.com>,
	zhanchengbin <zhanchengbin1@...wei.com>
Subject: [PATCH 02/20] ext4: prevent partial update of the extents path

From: Baokun Li <libaokun1@...wei.com>

In ext4_ext_rm_idx() and ext4_ext_correct_indexes(), there is no proper
rollback of already executed updates when updating a level of the extents
path fails, so we may get an inconsistent extents tree, which may trigger
some bad things in errors=continue mode.

Hence clear the verified bit of modified extents buffers if the tree fails
to be updated in ext4_ext_rm_idx() or ext4_ext_correct_indexes(), which
forces the extents buffers to be checked in ext4_valid_extent_entries(),
ensuring that the extents tree is consistent.

Signed-off-by: zhanchengbin <zhanchengbin1@...wei.com>
Link: https://lore.kernel.org/r/20230213080514.535568-3-zhanchengbin1@huawei.com/
Signed-off-by: Baokun Li <libaokun1@...wei.com>
---
 fs/ext4/extents.c | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index bff3666c891a..4d589d34b30e 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -1749,12 +1749,23 @@ static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode,
 			break;
 		err = ext4_ext_get_access(handle, inode, path + k);
 		if (err)
-			break;
+			goto clean;
 		path[k].p_idx->ei_block = border;
 		err = ext4_ext_dirty(handle, inode, path + k);
 		if (err)
-			break;
+			goto clean;
 	}
+	return 0;
+
+clean:
+	/*
+	 * The path[k].p_bh is either unmodified or with no verified bit
+	 * set (see ext4_ext_get_access()). So just clear the verified bit
+	 * of the successfully modified extents buffers, which will force
+	 * these extents to be checked to avoid using inconsistent data.
+	 */
+	while (++k < depth)
+		clear_buffer_verified(path[k].p_bh);
 
 	return err;
 }
@@ -2312,12 +2323,24 @@ static int ext4_ext_rm_idx(handle_t *handle, struct inode *inode,
 			break;
 		err = ext4_ext_get_access(handle, inode, path + k);
 		if (err)
-			break;
+			goto clean;
 		path[k].p_idx->ei_block = path[k + 1].p_idx->ei_block;
 		err = ext4_ext_dirty(handle, inode, path + k);
 		if (err)
-			break;
+			goto clean;
 	}
+	return 0;
+
+clean:
+	/*
+	 * The path[k].p_bh is either unmodified or with no verified bit
+	 * set (see ext4_ext_get_access()). So just clear the verified bit
+	 * of the successfully modified extents buffers, which will force
+	 * these extents to be checked to avoid using inconsistent data.
+	 */
+	while (++k < depth)
+		clear_buffer_verified(path[k].p_bh);
+
 	return err;
 }
 
-- 
2.39.2