[PATCH] ext4: set awu_max_opt to awu_max

[PATCH] ext4: set awu_max_opt to awu_max

[Pankaj Raghav]

commit 5d894321c49e ("fs: add atomic write unit max opt to statx")
added atomic write max optimal to statx. As XFS can support large atomic
writes through SW, max_opt exposes the value that will be HW accelerated
atomics.

As ext4 does not support SW atomics, set awu_max_opt to awu_max.

Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
 fs/ext4/inode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 26f0f9714f03..93056c971e74 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -6304,7 +6304,8 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path,
 			awu_max = sbi->s_awu_max;
 		}
 
-		generic_fill_statx_atomic_writes(stat, awu_min, awu_max, 0);
+		generic_fill_statx_atomic_writes(stat, awu_min, awu_max,
+						 awu_max);
 	}
 
 	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;

base-commit: d5ba62a0b130441bcabca59c2fd2d59e65360234
-- 
2.51.2

Re: [PATCH] ext4: set awu_max_opt to awu_max

[sashiko-bot]

> commit 5d894321c49e ("fs: add atomic write unit max opt to statx")
> added atomic write max optimal to statx. As XFS can support large atomic
> writes through SW, max_opt exposes the value that will be HW accelerated
> atomics.
> 
> As ext4 does not support SW atomics, set awu_max_opt to awu_max.
> 
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260910100829.2532894-1-p.raghav@samsung.com?part=1

Re: [PATCH] ext4: set awu_max_opt to awu_max

[Jan Kara]

On Thu 10-09-26 12:08:29, Pankaj Raghav wrote:
> commit 5d894321c49e ("fs: add atomic write unit max opt to statx")
> added atomic write max optimal to statx. As XFS can support large atomic
> writes through SW, max_opt exposes the value that will be HW accelerated
> atomics.
> 
> As ext4 does not support SW atomics, set awu_max_opt to awu_max.
> 
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>

Yes, I guess it's better to report it than not and let userspace guess. Feel
free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/ext4/inode.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 26f0f9714f03..93056c971e74 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -6304,7 +6304,8 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path,
>  			awu_max = sbi->s_awu_max;
>  		}
>  
> -		generic_fill_statx_atomic_writes(stat, awu_min, awu_max, 0);
> +		generic_fill_statx_atomic_writes(stat, awu_min, awu_max,
> +						 awu_max);
>  	}
>  
>  	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
> 
> base-commit: d5ba62a0b130441bcabca59c2fd2d59e65360234
> -- 
> 2.51.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] ext4: set awu_max_opt to awu_max

[Ritesh Harjani]

Pankaj Raghav <p.raghav@samsung.com> writes:

> commit 5d894321c49e ("fs: add atomic write unit max opt to statx")
> added atomic write max optimal to statx. As XFS can support large atomic
> writes through SW, max_opt exposes the value that will be HW accelerated
> atomics.
>
> As ext4 does not support SW atomics, set awu_max_opt to awu_max.
>

As per the man page the awu_max_opt=0 means:

    A value of zero indicates that stx_atomic_write_unit_max is the
    optimised limit.

[1]: https://man7.org/linux/man-pages/man2/statx.2.html

But the value of 0 isn't wrong either. Jan, added that it might be more
clear to report awu_max there instead of 0. So, if are going to do it -
let's add this info to the commit msg. So it doesn't look like we were
trying to fix anything here ;)

btw note that bdev_statx() still reports 0 for awu_max_opt.

With that please feel free to add:

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
>  fs/ext4/inode.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 26f0f9714f03..93056c971e74 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -6304,7 +6304,8 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path,
>  			awu_max = sbi->s_awu_max;
>  		}
>  
> -		generic_fill_statx_atomic_writes(stat, awu_min, awu_max, 0);
> +		generic_fill_statx_atomic_writes(stat, awu_min, awu_max,
> +						 awu_max);
>  	}
>  
>  	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
>
> base-commit: d5ba62a0b130441bcabca59c2fd2d59e65360234
> -- 
> 2.51.2

Re: [PATCH] ext4: set awu_max_opt to awu_max

[Ojaswin Mujoo]

On Thu, Sep 10, 2026 at 12:08:29PM +0200, Pankaj Raghav wrote:
> commit 5d894321c49e ("fs: add atomic write unit max opt to statx")
> added atomic write max optimal to statx. As XFS can support large atomic
> writes through SW, max_opt exposes the value that will be HW accelerated
> atomics.
> 
> As ext4 does not support SW atomics, set awu_max_opt to awu_max.
> 
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>

Hey Pankaj, I think 0 is allowed for backward compatibility as
highlighted in the commit you mentioned:
	...
	Masks STATX{_ATTR}_WRITE_ATOMIC can be used to get this new field. This is
  ok for older kernels which don't support this new field, as they would
  report 0 in this field (from zeroing in cp_statx()) already.
	...
	
But yeah sure, advertising it as awu_max is more clearer. 

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

Regards,
ojaswin


> ---
>  fs/ext4/inode.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 26f0f9714f03..93056c971e74 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -6304,7 +6304,8 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path,
>  			awu_max = sbi->s_awu_max;
>  		}
>  
> -		generic_fill_statx_atomic_writes(stat, awu_min, awu_max, 0);
> +		generic_fill_statx_atomic_writes(stat, awu_min, awu_max,
> +						 awu_max);
>  	}
>  
>  	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
> 
> base-commit: d5ba62a0b130441bcabca59c2fd2d59e65360234
> -- 
> 2.51.2
>