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authorBaokun Li <libaokun1@huawei.com>2022-05-28 14:00:16 +0300
committerTheodore Ts'o <tytso@mit.edu>2022-06-19 02:35:57 +0300
commitcf4ff938b47fc5c00b0ccce53a3b50eca9b32281 (patch)
tree8f5c001c273f043f954576f9917196398672e05b /fs/ext4
parenta08f789d2ab5242c07e716baf9a835725046be89 (diff)
downloadlinux-cf4ff938b47fc5c00b0ccce53a3b50eca9b32281.tar.xz
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>
Diffstat (limited to 'fs/ext4')
-rw-r--r--fs/ext4/mballoc.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 4d3740fdff90..9e06334771a3 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -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",