linux-ext4 - Re: [PATCH v3 6/7] ext4: Enable support for ext4 multi-fsblock atomic write using bigalloc

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Message-ID: <20250514162122.GI25655@frogsfrogsfrogs>
Date: Wed, 14 May 2025 09:21:22 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
Cc: linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
	Jan Kara <jack@...e.cz>, John Garry <john.g.garry@...cle.com>,
	Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v3 6/7] ext4: Enable support for ext4 multi-fsblock
 atomic write using bigalloc

On Fri, May 09, 2025 at 02:20:36AM +0530, Ritesh Harjani (IBM) wrote:
> Last couple of patches added the needed support for multi-fsblock atomic
> writes using bigalloc. This patch ensures that filesystem advertizes the
> needed atomic write unit min and max values for enabling multi-fsblock
> atomic write support with bigalloc.
> 
> Co-developed-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
> Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
> ---
>  fs/ext4/super.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 181934499624..508ea5cff1c7 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4442,12 +4442,12 @@ static int ext4_handle_clustersize(struct super_block *sb)
>  /*
>   * ext4_atomic_write_init: Initializes filesystem min & max atomic write units.
>   * @sb: super block
> - * TODO: Later add support for bigalloc
>   */
>  static void ext4_atomic_write_init(struct super_block *sb)
>  {
>  	struct ext4_sb_info *sbi = EXT4_SB(sb);
>  	struct block_device *bdev = sb->s_bdev;
> +	unsigned int clustersize = sb->s_blocksize;
>  
>  	if (!bdev_can_atomic_write(bdev))
>  		return;
> @@ -4455,9 +4455,12 @@ static void ext4_atomic_write_init(struct super_block *sb)
>  	if (!ext4_has_feature_extents(sb))
>  		return;
>  
> +	if (ext4_has_feature_bigalloc(sb))
> +		clustersize = EXT4_CLUSTER_SIZE(sb);

Doesn't EXT4_CLUSTER_SIZE return EXT4_BLOCK_SIZE(sb) (aka s_blocksize)
for !bigalloc filesystems?

Looks fine to me otherwise
Acked-by: "Darrick J. Wong" <djwong@...nel.org>

--D

> +
>  	sbi->s_awu_min = max(sb->s_blocksize,
>  			      bdev_atomic_write_unit_min_bytes(bdev));
> -	sbi->s_awu_max = min(sb->s_blocksize,
> +	sbi->s_awu_max = min(clustersize,
>  			      bdev_atomic_write_unit_max_bytes(bdev));
>  	if (sbi->s_awu_min && sbi->s_awu_max &&
>  	    sbi->s_awu_min <= sbi->s_awu_max) {
> -- 
> 2.49.0
> 
>