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Commit 260fc962 authored by Baokun Li's avatar Baokun Li Committed by Greg Kroah-Hartman
Browse files

ext4: avoid allocating blocks from corrupted group in ext4_mb_try_best_found() 



[ Upstream commit 4530b3660d396a646aad91a787b6ab37cf604b53 ]

Determine if the group block bitmap is corrupted before using ac_b_ex in
ext4_mb_try_best_found() to avoid allocating blocks from a group with a
corrupted block bitmap in the following concurrency and making the
situation worse.

ext4_mb_regular_allocator
  ext4_lock_group(sb, group)
  ext4_mb_good_group
   // check if the group bbitmap is corrupted
  ext4_mb_complex_scan_group
   // Scan group gets ac_b_ex but doesn't use it
  ext4_unlock_group(sb, group)
                           ext4_mark_group_bitmap_corrupted(group)
                           // The block bitmap was corrupted during
                           // the group unlock gap.
  ext4_mb_try_best_found
    ext4_lock_group(ac->ac_sb, group)
    ext4_mb_use_best_found
      mb_mark_used
      // Allocating blocks in block bitmap corrupted group

Signed-off-by: default avatarBaokun Li <libaokun1@huawei.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240104142040.2835097-7-libaokun1@huawei.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent bccb418e

fs/ext4/mballoc.c

+4 −0
Original line number Diff line number Diff line
@@ -1802,6 +1802,9 @@ int ext4_mb_try_best_found(struct ext4_allocation_context *ac, 
		return err;



	ext4_lock_group(ac->ac_sb, group);

	if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info)))

		goto out;



	max = mb_find_extent(e4b, ex.fe_start, ex.fe_len, &ex);



	if (max > 0) {
@@ -1809,6 +1812,7 @@ int ext4_mb_try_best_found(struct ext4_allocation_context *ac, 
		ext4_mb_use_best_found(ac, e4b);

	}



out:

	ext4_unlock_group(ac->ac_sb, group);

	ext4_mb_unload_buddy(e4b);