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ext4: correct the journal credits calculations of allocating blocks

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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>
Link: https://patch.msgid.link/20250512063319.3539411-6-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Zhang Yi 2025-05-12 14:33:16 +08:00 • committed by Theodore Ts'o
parent d6bf294773
commit 0e32d86170
2 changed files with 7 additions and 8 deletions
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5
fs/ext4/extents.c
View file

@ -2409,9 +2409,10 @@ int ext4_ext_index_trans_blocks(struct inode *inode, int extents)
* the time we actually modify the tree. Assume the worst case.
*/
if (extents <= 1)
index = EXT4_MAX_EXTENT_DEPTH * 2;
index = (EXT4_MAX_EXTENT_DEPTH * 2) + extents;
else
index = EXT4_MAX_EXTENT_DEPTH * 3;
index = (EXT4_MAX_EXTENT_DEPTH * 3) +
DIV_ROUND_UP(extents, ext4_ext_space_block(inode, 0));
return index;
}

10
fs/ext4/inode.c
View file

@ -5844,18 +5844,16 @@ 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;
@ -5863,7 +5861,7 @@ 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);