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| author | Baokun Li <libaokun1@huawei.com> | 2025-11-21 17:06:41 +0800 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2025-11-28 22:35:27 -0500 |
| commit | 6117f1806a7328e8d316eeeac66b2ba4e4539ba5 (patch) | |
| tree | 65d1ad6183330b9e10152c5ae09d33e83abc2497 /fs/ext4 | |
| parent | 2a8de76b2b0f84333a2778db04ce51811c260d9d (diff) | |
| download | tip-6117f1806a7328e8d316eeeac66b2ba4e4539ba5.tar.gz | |
ext4: support large block size in ext4_mb_load_buddy_gfp()
Currently, ext4_mb_load_buddy_gfp() uses blocks_per_page to calculate the
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, if buddy and bitmap land in the same folio, we get that folio’s ref
instead of looking it up again before updating the buddy.
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: <20251121090654.631996-12-libaokun@huaweicloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4')
| -rw-r--r-- | fs/ext4/mballoc.c | 27 |
1 files changed, 16 insertions, 11 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 65335248825ce4..38af89f5da5661 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -1659,17 +1659,15 @@ err: /* * Locking note: This routine calls ext4_mb_init_cache(), which takes the - * block group lock of all groups for this page; do not hold the BG lock when + * block group lock of all groups for this folio; do not hold the BG lock when * calling this routine! */ static noinline_for_stack int ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group, struct ext4_buddy *e4b, gfp_t gfp) { - int blocks_per_page; int block; int pnum; - int poff; struct folio *folio; int ret; struct ext4_group_info *grp; @@ -1679,7 +1677,6 @@ ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group, might_sleep(); mb_debug(sb, "load group %u\n", group); - blocks_per_page = PAGE_SIZE / sb->s_blocksize; grp = ext4_get_group_info(sb, group); if (!grp) return -EFSCORRUPTED; @@ -1707,8 +1704,7 @@ ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group, * 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); /* Avoid locking the folio in the fast path ... */ folio = __filemap_get_folio(inode->i_mapping, pnum, FGP_ACCESSED, 0); @@ -1740,7 +1736,8 @@ ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group, goto err; } mb_cmp_bitmaps(e4b, folio_address(folio) + - (poff * sb->s_blocksize)); + offset_in_folio(folio, + EXT4_LBLK_TO_B(inode, block))); } folio_unlock(folio); } @@ -1756,12 +1753,18 @@ ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group, /* Folios marked accessed already */ 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)); block++; - pnum = block / blocks_per_page; - poff = block % blocks_per_page; + pnum = EXT4_LBLK_TO_PG(inode, block); + /* buddy and bitmap are on the same folio? */ + if (folio_contains(folio, pnum)) { + folio_get(folio); + goto update_buddy; + } + /* we need another folio for the buddy */ folio = __filemap_get_folio(inode->i_mapping, pnum, FGP_ACCESSED, 0); if (IS_ERR(folio) || !folio_test_uptodate(folio)) { if (!IS_ERR(folio)) @@ -1796,9 +1799,11 @@ ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group, goto err; } +update_buddy: /* Folios marked accessed already */ e4b->bd_buddy_folio = folio; - e4b->bd_buddy = folio_address(folio) + (poff * sb->s_blocksize); + e4b->bd_buddy = folio_address(folio) + + offset_in_folio(folio, EXT4_LBLK_TO_B(inode, block)); return 0; |