[PATCH v2 5/8] ext4: correct the journal credits calculations of allocating blocks

Zhang Yi
2025-05-12T06:44:52Z

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

The journal credits calculation in ext4_ext_index_trans_blocks() is
currently inadequate. It only multiplies the depth of the extents tree
and doesn't account for the blocks that may be required for adding the
leaf extents themselves.

After enabling large folios, we can easily run out of handle credits,
triggering a warning in jbd2_journal_dirty_metadata() on filesystems
with a 1KB block size. This occurs because we may need more extents when
iterating through each large folio in
ext4_do_writepages()->mpage_map_and_submit_extent(). Therefore, we
should modify ext4_ext_index_trans_blocks() to include a count of the
leaf extents in the worst case as well.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
fs/ext4/extents.c | 5 +++--
fs/ext4/inode.c | 10 ++++------
2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c616a16a9f36..e759941bd262 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2405,9 +2405,10 @@ int ext4_ext_index_trans_blocks(struct inode *inode, int extents)
depth = ext_depth(inode);

if (extents <= 1)
- index = depth * 2;
+ index = depth * 2 + extents;
else
- index = depth * 3;
+ index = depth * 3 +
+ DIV_ROUND_UP(extents, ext4_ext_space_block(inode, 0));

return index;
}
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ffbf444b56d4..3e962a760d71 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5792,18 +5792,16 @@ static int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
int ret;

/*
- * How many index blocks need to touch to map @lblocks logical blocks
- * to @pextents physical extents?
+ * How many index and lead blocks need to touch to map @lblocks
+ * logical blocks to @pextents physical extents?
*/
idxblocks = ext4_index_trans_blocks(inode, lblocks, pextents);

- ret = idxblocks;
-
/*
* Now let's see how many group bitmaps and group descriptors need
* to account
*/
- groups = idxblocks + pextents;
+ groups = idxblocks;
gdpblocks = groups;
if (groups > ngroups)
groups = ngroups;
@@ -5811,7 +5809,7 @@ static int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
gdpblocks = EXT4_SB(inode->i_sb)->s_gdb_count;

/* bitmaps and block group descriptor blocks */
- ret += groups + gdpblocks;
+ ret = idxblocks + groups + gdpblocks;

/* Blocks for super block, inode, quota and xattr blocks */
ret += EXT4_META_TRANS_BLOCKS(inode->i_sb);
--
2.46.1