Commit 0e32d861 authored by Zhang Yi's avatar Zhang Yi Committed by Theodore Ts'o
Browse files

ext4: correct the journal credits calculations of allocating blocks 



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: default avatarZhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20250512063319.3539411-6-yi.zhang@huaweicloud.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent d6bf2947

fs/ext4/extents.c

+3 −2
Original line number Diff line number Diff line
@@ -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;

}

fs/ext4/inode.c

+4 −6
Original line number Diff line number Diff line
@@ -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);