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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: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Ritesh Harjani <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20220528110017.354175-3-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Baokun Li 2022-05-28 19:00:16 +08:00 committed by Theodore Ts'o
parent a08f789d2a
commit cf4ff938b4
1 changed files with 16 additions and 1 deletions
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17
fs/ext4/mballoc.c
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@ -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",