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Date:   Mon, 13 Feb 2023 12:05:21 +0800
From:   zhanchengbin <zhanchengbin1@...wei.com>
To:     <tytso@....edu>, <jack@...e.com>
CC:     <linux-ext4@...r.kernel.org>, <yi.zhang@...wei.com>,
        <linfeilong@...wei.com>, <liuzhiqiang26@...wei.com>,
        zhanchengbin <zhanchengbin1@...wei.com>
Subject: [PATCH v4 1/2] ext4: fix inode tree inconsistency caused by ENOMEM in ext4_split_extent_at

If ENOMEM fails when the extent is splitting, we need to restore the length
of the split extent.
In the call stack of 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>
---
 fs/ext4/extents.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 9de1c9d1a13d..0f95e857089e 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -935,6 +935,7 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block,
 
 		bh = read_extent_tree_block(inode, path[ppos].p_idx, --i, flags);
 		if (IS_ERR(bh)) {
+			EXT4_ERROR_INODE(inode, "IO error reading extent block");
 			ret = PTR_ERR(bh);
 			goto err;
 		}
@@ -3251,7 +3252,7 @@ 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

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