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ext4: support large block size in ext4_mb_get_buddy_page_lock()

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Currently, ext4_mb_get_buddy_page_lock() uses blocks_per_page to calculate
folio index and offset. However, when blocksize is larger than PAGE_SIZE,
blocks_per_page becomes zero, leading to a potential division-by-zero bug.

To support BS > PS, use bytes to compute folio index and offset within
folio to get rid of blocks_per_page.

Also, since ext4_mb_get_buddy_page_lock() already fully supports folio,
rename it to ext4_mb_get_buddy_folio_lock().

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Message-ID: <20251121090654.631996-13-libaokun@huaweicloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Baokun Li
2025-11-21 17:06:42 +08:00
committed by Theodore Ts'o
parent 6117f1806a
commit 3938fc29f8
1 changed files with 22 additions and 20 deletions
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42
fs/ext4/mballoc.c
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@@ -1527,50 +1527,52 @@ out:
}
/*
* Lock the buddy and bitmap pages. This make sure other parallel init_group
* on the same buddy page doesn't happen whild holding the buddy page lock.
* Return locked buddy and bitmap pages on e4b struct. If buddy and bitmap
* are on the same page e4b->bd_buddy_folio is NULL and return value is 0.
* Lock the buddy and bitmap folios. This makes sure other parallel init_group
* on the same buddy folio doesn't happen while holding the buddy folio lock.
* Return locked buddy and bitmap folios on e4b struct. If buddy and bitmap
* are on the same folio e4b->bd_buddy_folio is NULL and return value is 0.
*/
static int ext4_mb_get_buddy_page_lock(struct super_block *sb,
static int ext4_mb_get_buddy_folio_lock(struct super_block *sb,
ext4_group_t group, struct ext4_buddy *e4b, gfp_t gfp)
{
struct inode *inode = EXT4_SB(sb)->s_buddy_cache;
int block, pnum, poff;
int blocks_per_page;
int block, pnum;
struct folio *folio;
e4b->bd_buddy_folio = NULL;
e4b->bd_bitmap_folio = NULL;
blocks_per_page = PAGE_SIZE / sb->s_blocksize;
/*
* the buddy cache inode stores the block bitmap
* and buddy information in consecutive blocks.
* So for each group we need two blocks.
*/
block = group * 2;
pnum = block / blocks_per_page;
poff = block % blocks_per_page;
pnum = EXT4_LBLK_TO_PG(inode, block);
folio = __filemap_get_folio(inode->i_mapping, pnum,
FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp);
if (IS_ERR(folio))
return PTR_ERR(folio);
BUG_ON(folio->mapping != inode->i_mapping);
WARN_ON_ONCE(folio_size(folio) < sb->s_blocksize);
e4b->bd_bitmap_folio = folio;
e4b->bd_bitmap = folio_address(folio) + (poff * sb->s_blocksize);
e4b->bd_bitmap = folio_address(folio) +
offset_in_folio(folio, EXT4_LBLK_TO_B(inode, block));
if (blocks_per_page >= 2) {
/* buddy and bitmap are on the same page */
block++;
pnum = EXT4_LBLK_TO_PG(inode, block);
if (folio_contains(folio, pnum)) {
/* buddy and bitmap are on the same folio */
return 0;
}
/* blocks_per_page == 1, hence we need another page for the buddy */
folio = __filemap_get_folio(inode->i_mapping, block + 1,
/* we need another folio for the buddy */
folio = __filemap_get_folio(inode->i_mapping, pnum,
FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp);
if (IS_ERR(folio))
return PTR_ERR(folio);
BUG_ON(folio->mapping != inode->i_mapping);
WARN_ON_ONCE(folio_size(folio) < sb->s_blocksize);
e4b->bd_buddy_folio = folio;
return 0;
}
@@ -1609,14 +1611,14 @@ int ext4_mb_init_group(struct super_block *sb, ext4_group_t group, gfp_t gfp)
/*
* This ensures that we don't reinit the buddy cache
* page which map to the group from which we are already
* folio which map to the group from which we are already
* allocating. If we are looking at the buddy cache we would
* have taken a reference using ext4_mb_load_buddy and that
* would have pinned buddy page to page cache.
* The call to ext4_mb_get_buddy_page_lock will mark the
* page accessed.
* would have pinned buddy folio to page cache.
* The call to ext4_mb_get_buddy_folio_lock will mark the
* folio accessed.
*/
ret = ext4_mb_get_buddy_page_lock(sb, group, &e4b, gfp);
ret = ext4_mb_get_buddy_folio_lock(sb, group, &e4b, gfp);
if (ret || !EXT4_MB_GRP_NEED_INIT(this_grp)) {
/*
* somebody initialized the group