Commit cf4ff938 authored by Baokun Li's avatar Baokun Li Committed by Theodore Ts'o
Browse files

ext4: correct the judgment of BUG in ext4_mb_normalize_request 



ext4_mb_normalize_request() can move logical start of allocated blocks
to reduce fragmentation and better utilize preallocation. However logical
block requested as a start of allocation (ac->ac_o_ex.fe_logical) should
always be covered by allocated blocks so we should check that by
modifying and to or in the assertion.

Signed-off-by: default avatarBaokun Li <libaokun1@huawei.com>
Reviewed-by: default avatarRitesh Harjani <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20220528110017.354175-3-libaokun1@huawei.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent a08f789d

fs/ext4/mballoc.c

+16 −1
Original line number Diff line number Diff line
@@ -4185,7 +4185,22 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac, 
	}

	rcu_read_unlock();



	if (start + size <= ac->ac_o_ex.fe_logical &&

	/*

	 * In this function "start" and "size" are normalized for better

	 * alignment and length such that we could preallocate more blocks.

	 * This normalization is done such that original request of

	 * ac->ac_o_ex.fe_logical & fe_len should always lie within "start" and

	 * "size" boundaries.

	 * (Note fe_len can be relaxed since FS block allocation API does not

	 * provide gurantee on number of contiguous blocks allocation since that

	 * depends upon free space left, etc).

	 * In case of inode pa, later we use the allocated blocks

	 * [pa_start + fe_logical - pa_lstart, fe_len/size] from the preallocated

	 * range of goal/best blocks [start, size] to put it at the

	 * ac_o_ex.fe_logical extent of this inode.

	 * (See ext4_mb_use_inode_pa() for more details)

	 */

	if (start + size <= ac->ac_o_ex.fe_logical ||

			start > ac->ac_o_ex.fe_logical) {

		ext4_msg(ac->ac_sb, KERN_ERR,

			 "start %lu, size %lu, fe_logical %lu",