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* [PATCH] ext4: Don't use CR_BEST_AVAIL_LEN for non-regular files
@ 2023-07-16 14:03 Ritesh Harjani (IBM)
  2023-07-16 15:37 ` Ojaswin Mujoo
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Ritesh Harjani (IBM) @ 2023-07-16 14:03 UTC (permalink / raw)
  To: linux-ext4; +Cc: Ojaswin Mujoo, Ritesh Harjani (IBM), Eric Whitney

Using CR_BEST_AVAIL_LEN only make sense for regular files, as for
non-regular files we never normalize the allocation request length i.e.
goal len is same as original length (ac_g_ex.fe_len == ac_o_ex.fe_len).

Hence there is no scope of trimming the goal length to make it
satisfy original request len. Thus this patch avoids using
CR_BEST_AVAIL_LEN criteria for non-regular files request.

Fixes: 33122aa930f1 ("ext4: Add allocation criteria 1.5 (CR1_5)")
Reported-by: Eric Whitney <enwlinux@gmail.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 fs/ext4/mballoc.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 3ab37533349f..bc004f5d3f3c 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -975,7 +975,18 @@ static void ext4_mb_choose_next_group_goal_fast(struct ext4_allocation_context *
 		*group = grp->bb_group;
 		ac->ac_flags |= EXT4_MB_CR_GOAL_LEN_FAST_OPTIMIZED;
 	} else {
-		*new_cr = CR_BEST_AVAIL_LEN;
+		/*
+		 * CR_BEST_AVAIL_LEN works based on the concept that we have
+		 * a larger normalized goal len request which can be trimmed to
+		 * a smaller goal len such that it can still satisfy original
+		 * request len. However, allocation request for non-regular
+		 * files never gets normalized.
+		 * See function ext4_mb_normalize_request() (EXT4_MB_HINT_DATA).
+		 */
+		if (ac->ac_flags & EXT4_MB_HINT_DATA)
+			*new_cr = CR_BEST_AVAIL_LEN;
+		else
+			*new_cr = CR_GOAL_LEN_SLOW;
 	}
 }

--
2.40.1


^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [PATCH] ext4: Don't use CR_BEST_AVAIL_LEN for non-regular files
  2023-07-16 14:03 [PATCH] ext4: Don't use CR_BEST_AVAIL_LEN for non-regular files Ritesh Harjani (IBM)
@ 2023-07-16 15:37 ` Ojaswin Mujoo
  2023-07-17 21:28 ` Eric Whitney
  2023-08-05 12:20 ` Theodore Ts'o
  2 siblings, 0 replies; 4+ messages in thread
From: Ojaswin Mujoo @ 2023-07-16 15:37 UTC (permalink / raw)
  To: Ritesh Harjani (IBM); +Cc: linux-ext4, Eric Whitney

On Sun, Jul 16, 2023 at 07:33:34PM +0530, Ritesh Harjani (IBM) wrote:
> Using CR_BEST_AVAIL_LEN only make sense for regular files, as for
> non-regular files we never normalize the allocation request length i.e.
> goal len is same as original length (ac_g_ex.fe_len == ac_o_ex.fe_len).
> 
> Hence there is no scope of trimming the goal length to make it
> satisfy original request len. Thus this patch avoids using
> CR_BEST_AVAIL_LEN criteria for non-regular files request.
> 
> Fixes: 33122aa930f1 ("ext4: Add allocation criteria 1.5 (CR1_5)")
> Reported-by: Eric Whitney <enwlinux@gmail.com>
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> ---
Hi Ritesh,

patch looks good to me. Feel free to add:

Reviewed-by: Ojaswin Mujoo <ojaswin.linux.ibm.com>

Regards,
ojaswin
>  fs/ext4/mballoc.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 3ab37533349f..bc004f5d3f3c 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -975,7 +975,18 @@ static void ext4_mb_choose_next_group_goal_fast(struct ext4_allocation_context *
>  		*group = grp->bb_group;
>  		ac->ac_flags |= EXT4_MB_CR_GOAL_LEN_FAST_OPTIMIZED;
>  	} else {
> -		*new_cr = CR_BEST_AVAIL_LEN;
> +		/*
> +		 * CR_BEST_AVAIL_LEN works based on the concept that we have
> +		 * a larger normalized goal len request which can be trimmed to
> +		 * a smaller goal len such that it can still satisfy original
> +		 * request len. However, allocation request for non-regular
> +		 * files never gets normalized.
> +		 * See function ext4_mb_normalize_request() (EXT4_MB_HINT_DATA).
> +		 */
> +		if (ac->ac_flags & EXT4_MB_HINT_DATA)
> +			*new_cr = CR_BEST_AVAIL_LEN;
> +		else
> +			*new_cr = CR_GOAL_LEN_SLOW;
>  	}
>  }
> 
> --
> 2.40.1
> 

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH] ext4: Don't use CR_BEST_AVAIL_LEN for non-regular files
  2023-07-16 14:03 [PATCH] ext4: Don't use CR_BEST_AVAIL_LEN for non-regular files Ritesh Harjani (IBM)
  2023-07-16 15:37 ` Ojaswin Mujoo
@ 2023-07-17 21:28 ` Eric Whitney
  2023-08-05 12:20 ` Theodore Ts'o
  2 siblings, 0 replies; 4+ messages in thread
From: Eric Whitney @ 2023-07-17 21:28 UTC (permalink / raw)
  To: Ritesh Harjani (IBM); +Cc: linux-ext4, Ojaswin Mujoo, Eric Whitney

* Ritesh Harjani (IBM) <ritesh.list@gmail.com>:
> Using CR_BEST_AVAIL_LEN only make sense for regular files, as for
> non-regular files we never normalize the allocation request length i.e.
> goal len is same as original length (ac_g_ex.fe_len == ac_o_ex.fe_len).
> 
> Hence there is no scope of trimming the goal length to make it
> satisfy original request len. Thus this patch avoids using
> CR_BEST_AVAIL_LEN criteria for non-regular files request.
> 
> Fixes: 33122aa930f1 ("ext4: Add allocation criteria 1.5 (CR1_5)")
> Reported-by: Eric Whitney <enwlinux@gmail.com>
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> ---
>  fs/ext4/mballoc.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 3ab37533349f..bc004f5d3f3c 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -975,7 +975,18 @@ static void ext4_mb_choose_next_group_goal_fast(struct ext4_allocation_context *
>  		*group = grp->bb_group;
>  		ac->ac_flags |= EXT4_MB_CR_GOAL_LEN_FAST_OPTIMIZED;
>  	} else {
> -		*new_cr = CR_BEST_AVAIL_LEN;
> +		/*
> +		 * CR_BEST_AVAIL_LEN works based on the concept that we have
> +		 * a larger normalized goal len request which can be trimmed to
> +		 * a smaller goal len such that it can still satisfy original
> +		 * request len. However, allocation request for non-regular
> +		 * files never gets normalized.
> +		 * See function ext4_mb_normalize_request() (EXT4_MB_HINT_DATA).
> +		 */
> +		if (ac->ac_flags & EXT4_MB_HINT_DATA)
> +			*new_cr = CR_BEST_AVAIL_LEN;
> +		else
> +			*new_cr = CR_GOAL_LEN_SLOW;
>  	}
>  }
> 
> --
> 2.40.1
>

Works for me on 6.5-rc2 with this patch applied - 500/500 generic/269 trials
passed on bigalloc_1k.

Tested-by: Eric Whitney <enwlinux@gmail.com>

Thanks!
Eric

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH] ext4: Don't use CR_BEST_AVAIL_LEN for non-regular files
  2023-07-16 14:03 [PATCH] ext4: Don't use CR_BEST_AVAIL_LEN for non-regular files Ritesh Harjani (IBM)
  2023-07-16 15:37 ` Ojaswin Mujoo
  2023-07-17 21:28 ` Eric Whitney
@ 2023-08-05 12:20 ` Theodore Ts'o
  2 siblings, 0 replies; 4+ messages in thread
From: Theodore Ts'o @ 2023-08-05 12:20 UTC (permalink / raw)
  To: linux-ext4, Ritesh Harjani (IBM)
  Cc: Theodore Ts'o, Ojaswin Mujoo, Eric Whitney


On Sun, 16 Jul 2023 19:33:34 +0530, Ritesh Harjani (IBM) wrote:
> Using CR_BEST_AVAIL_LEN only make sense for regular files, as for
> non-regular files we never normalize the allocation request length i.e.
> goal len is same as original length (ac_g_ex.fe_len == ac_o_ex.fe_len).
> 
> Hence there is no scope of trimming the goal length to make it
> satisfy original request len. Thus this patch avoids using
> CR_BEST_AVAIL_LEN criteria for non-regular files request.
> 
> [...]

Applied, thanks!

[1/1] ext4: Don't use CR_BEST_AVAIL_LEN for non-regular files
      commit: 772c9f691dcf3a487f29ddb90a5a15c78d7328e1

Best regards,
-- 
Theodore Ts'o <tytso@mit.edu>

^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2023-08-05 12:20 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2023-07-16 14:03 [PATCH] ext4: Don't use CR_BEST_AVAIL_LEN for non-regular files Ritesh Harjani (IBM)
2023-07-16 15:37 ` Ojaswin Mujoo
2023-07-17 21:28 ` Eric Whitney
2023-08-05 12:20 ` Theodore Ts'o

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