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Date:   Wed, 4 Aug 2021 17:32:21 +0200
From:   Jan Kara <jack@suse.cz>
To:     Wang Jianchao <jianchao.wan9@gmail.com>
Cc:     linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        tytso@mit.edu, adilger.kernel@dilger.ca
Subject: Re: [PATCH V3 5/5] ext4: make fallocate retry when err is ENOSPC
Message-ID: <20210804153221.GK4578@quack2.suse.cz>
References: <20210724074124.25731-1-jianchao.wan9@gmail.com>
 <20210724074124.25731-6-jianchao.wan9@gmail.com>
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On Sat 24-07-21 15:41:24, Wang Jianchao wrote:
> From: Wang Jianchao <wangjianchao@kuaishou.com>
> 
> The blocks may be waiting for journal commit to be freed back to
> mb buddy. Let fallocate wait and retry in that case.
> 
> Signed-off-by: Wang Jianchao <wangjianchao@kuaishou.com>

Did you really observe this? Because the retry is already handled in
ext4_alloc_file_blocks() that's used by ext4_fallocate(). So no retry
should be needed there.

								Honza

> ---
>  fs/ext4/extents.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 92ad64b89d9b..ad0b874d3448 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -4635,7 +4635,7 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>  	struct inode *inode = file_inode(file);
>  	loff_t new_size = 0;
>  	unsigned int max_blocks;
> -	int ret = 0;
> +	int ret = 0, retries = 0;
>  	int flags;
>  	ext4_lblk_t lblk;
>  	unsigned int blkbits = inode->i_blkbits;
> @@ -4656,6 +4656,7 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>  		     FALLOC_FL_INSERT_RANGE))
>  		return -EOPNOTSUPP;
>  
> +retry:
>  	ext4_fc_start_update(inode);
>  
>  	if (mode & FALLOC_FL_PUNCH_HOLE) {
> @@ -4722,6 +4723,9 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>  	trace_ext4_fallocate_exit(inode, offset, max_blocks, ret);
>  exit:
>  	ext4_fc_stop_update(inode);
> +	if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
> +		goto retry;
> +
>  	return ret;
>  }
>  
> -- 
> 2.17.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR