diff mbox series

[03/21] ext4: avoid to use preallocated blocks if EXT4_MB_HINT_GOAL_ONLY is set

Message ID 20230209194825.511043-4-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 
  ext4_mb_use_preallocated will ignore the demand to alloc at goal block
only. Return false if EXT4_MB_HINT_GOAL_ONLY is set before use
preallocated blocks in ext4_mb_use_preallocated.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
---
 fs/ext4/mballoc.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Ojaswin Mujoo Feb. 13, 2023, 8:38 a.m. UTC | #1 
On Fri, Feb 10, 2023 at 03:48:07AM +0800, Kemeng Shi wrote:
> ext4_mb_use_preallocated will ignore the demand to alloc at goal block
> only. Return false if EXT4_MB_HINT_GOAL_ONLY is set before use
> preallocated blocks in ext4_mb_use_preallocated.
> 
> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
> ---
>  fs/ext4/mballoc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 375d9655b525..352ac9139fee 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4368,6 +4368,9 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
>  	if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
>  		return false;
>  
> +	if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
> +		return false;
> +
>  	/* first, try per-file preallocation */
>  	rcu_read_lock();
>  	list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
> -- 
> 2.30.0
> 
So with the flag, even when we request for a logical/goal block
combination that can be satisfied by one of the inode PAs in the list,
we would still exit early and the allocation would eventually fail since
the goal block would be marked "in-use" in the buddy. This doesn't seem
to be desirable.

Maybe instead of exiting early we should try to find a PA that satisfies
the logical block we are asking for and then incase of
EXT4_MB_HINT_GOAL_ONLY, we can add a check to see if the physical block
of the PA corresponds to the goal block. Would like to hear your
thoughts on this.

Regards,
ojaswin
Kemeng Shi Feb. 13, 2023, 1:27 p.m. UTC | #2 
on 2/13/2023 4:38 PM, Ojaswin Mujoo wrote:
> On Fri, Feb 10, 2023 at 03:48:07AM +0800, Kemeng Shi wrote:
>> ext4_mb_use_preallocated will ignore the demand to alloc at goal block
>> only. Return false if EXT4_MB_HINT_GOAL_ONLY is set before use
>> preallocated blocks in ext4_mb_use_preallocated.
>>
>> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
>> ---
>>  fs/ext4/mballoc.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>> index 375d9655b525..352ac9139fee 100644
>> --- a/fs/ext4/mballoc.c
>> +++ b/fs/ext4/mballoc.c
>> @@ -4368,6 +4368,9 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
>>  	if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
>>  		return false;
>>  
>> +	if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
>> +		return false;
>> +
>>  	/* first, try per-file preallocation */
>>  	rcu_read_lock();
>>  	list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
>> -- 
>> 2.30.0
>>
> So with the flag, even when we request for a logical/goal block
> combination that can be satisfied by one of the inode PAs in the list,
> we would still exit early and the allocation would eventually fail since
> the goal block would be marked "in-use" in the buddy. This doesn't seem
> to be desirable.
> 
> Maybe instead of exiting early we should try to find a PA that satisfies
> the logical block we are asking for and then incase of
> EXT4_MB_HINT_GOAL_ONLY, we can add a check to see if the physical block
> of the PA corresponds to the goal block. Would like to hear your
> thoughts on this.
Yes, this is a more thoughtful, I will improve this in next version.
Besides, maybe we should also test length if EXT4_MB_HINT_MERGE is set
as ext4_mb_find_by_goal do.

> Regards,
> ojaswin
>
diff mbox series

Patch

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 375d9655b525..352ac9139fee 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4368,6 +4368,9 @@  ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
 	if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
 		return false;
 
+	if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
+		return false;
+
 	/* first, try per-file preallocation */
 	rcu_read_lock();
 	list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {