linux-ext4 - [PATCH] ext4: fix inode tree inconsistency caused by ENOMEM

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Message-ID: <20230103022812.130603-1-zhanchengbin1@huawei.com>
Date:   Tue, 3 Jan 2023 10:28:12 +0800
From:   zhanchengbin <zhanchengbin1@...wei.com>
To:     <tytso@....edu>, <jack@...e.com>
CC:     <linux-ext4@...r.kernel.org>, <yi.zhang@...wei.com>,
        <yebin10@...wei.com>, <linfeilong@...wei.com>,
        <liuzhiqiang26@...wei.com>, zhanchengbin <zhanchengbin1@...wei.com>
Subject: [PATCH] ext4: fix inode tree inconsistency caused by ENOMEM

If ENOMEM fails when the extent is splitting, we need to restore the length
of the split extent.
In the ext4_split_extent_at function, only in ext4_ext_create_new_leaf will
it alloc memory and change the shape of the extent tree,even if an ENOMEM
is returned at this time, the extent tree is still self-consistent, Just
restore the split extent lens in the function ext4_split_extent_at.

ext4_split_extent_at
 ext4_ext_insert_extent
  ext4_ext_create_new_leaf
   1)ext4_ext_split
     ext4_find_extent
   2)ext4_ext_grow_indepth
     ext4_find_extent

Signed-off-by: zhanchengbin <zhanchengbin1@...wei.com>
---
 Another solution is to add the __GFP_NOFAIL flag when allocating memory.

 fs/ext4/extents.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 9de1c9d1a13d..3559ea6b0781 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3251,7 +3251,7 @@ static int ext4_split_extent_at(handle_t *handle,
 		ext4_ext_mark_unwritten(ex2);
 
 	err = ext4_ext_insert_extent(handle, inode, ppath, &newex, flags);
-	if (err != -ENOSPC && err != -EDQUOT)
+	if (err != -ENOSPC && err != -EDQUOT && err != -ENOMEM)
 		goto out;
 
 	if (EXT4_EXT_MAY_ZEROOUT & split_flag) {
-- 
2.31.1