diff mbox series

[05/21] ext4: correct calculation of s_mb_preallocated

Message ID 20230209194825.511043-6-shikemeng@huaweicloud.com
State New
Headers
Series Some bugfix and cleanup to mballoc |

Commit Message

Kemeng Shi Feb. 9, 2023, 7:48 p.m. UTC 
  We will add pa_free to s_mb_preallocated when new ext4_prealloc_space is
created. In ext4_mb_new_inode_pa, we will call ext4_mb_use_inode_pa
before adding pa_free to s_mb_preallocated. However, ext4_mb_use_inode_pa
will consume pa_free for block allocation which triggerred the creation
of ext4_prealloc_space. Add pa_free to s_mb_preallocated before
ext4_mb_use_inode_pa to correct calculation of s_mb_preallocated.
There is no such problem in ext4_mb_new_group_pa as pa_free of group pa
is consumed in ext4_mb_release_context instead of ext4_mb_use_group_pa.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
---
 fs/ext4/mballoc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Ojaswin Mujoo Feb. 13, 2023, 7:04 a.m. UTC | #1 
On Fri, Feb 10, 2023 at 03:48:09AM +0800, Kemeng Shi wrote:
> We will add pa_free to s_mb_preallocated when new ext4_prealloc_space is
> created. In ext4_mb_new_inode_pa, we will call ext4_mb_use_inode_pa
> before adding pa_free to s_mb_preallocated. However, ext4_mb_use_inode_pa
> will consume pa_free for block allocation which triggerred the creation
> of ext4_prealloc_space. Add pa_free to s_mb_preallocated before
> ext4_mb_use_inode_pa to correct calculation of s_mb_preallocated.
> There is no such problem in ext4_mb_new_group_pa as pa_free of group pa
> is consumed in ext4_mb_release_context instead of ext4_mb_use_group_pa.
> 
> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
> ---
>  fs/ext4/mballoc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index f24f80ecf318..2bffc93778d5 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4670,8 +4670,8 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
>  		 pa->pa_len, pa->pa_lstart);
>  	trace_ext4_mb_new_inode_pa(ac, pa);
>  
> -	ext4_mb_use_inode_pa(ac, pa);
>  	atomic_add(pa->pa_free, &sbi->s_mb_preallocated);
> +	ext4_mb_use_inode_pa(ac, pa);
>  
>  	ei = EXT4_I(ac->ac_inode);
>  	grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group);
> -- 
> 2.30.0
> 
My understanding is that s_mb_preallocated is for all the blocks we ever preallocated and
so we need to add 'original' pa_len instead of (pa_len - best_len).

Hence, the patch looks correct to me. Feel free to add:

Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
diff mbox series

Patch

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index f24f80ecf318..2bffc93778d5 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4670,8 +4670,8 @@  ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
 		 pa->pa_len, pa->pa_lstart);
 	trace_ext4_mb_new_inode_pa(ac, pa);
 
-	ext4_mb_use_inode_pa(ac, pa);
 	atomic_add(pa->pa_free, &sbi->s_mb_preallocated);
+	ext4_mb_use_inode_pa(ac, pa);
 
 	ei = EXT4_I(ac->ac_inode);
 	grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group);