linux-kernel - Re: [PATCH 16/19] btrfs: wait existing extents before truncating

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Date:   Thu, 13 Jun 2019 10:25:58 -0400
From:   Josef Bacik <josef@...icpanda.com>
To:     Naohiro Aota <naohiro.aota@....com>
Cc:     linux-btrfs@...r.kernel.org, David Sterba <dsterba@...e.com>,
        Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        Qu Wenruo <wqu@...e.com>, Nikolay Borisov <nborisov@...e.com>,
        linux-kernel@...r.kernel.org, Hannes Reinecke <hare@...e.com>,
        linux-fsdevel@...r.kernel.org,
        Damien Le Moal <damien.lemoal@....com>,
        Matias Bjørling <mb@...htnvm.io>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Bart Van Assche <bvanassche@....org>
Subject: Re: [PATCH 16/19] btrfs: wait existing extents before truncating

On Fri, Jun 07, 2019 at 10:10:22PM +0900, Naohiro Aota wrote:
> When truncating a file, file buffers which have already been allocated but
> not yet written may be truncated.  Truncating these buffers could cause
> breakage of a sequential write pattern in a block group if the truncated
> blocks are for example followed by blocks allocated to another file. To
> avoid this problem, always wait for write out of all unwritten buffers
> before proceeding with the truncate execution.
> 
> Signed-off-by: Naohiro Aota <naohiro.aota@....com>
> ---
>  fs/btrfs/inode.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 89542c19d09e..4e8c7921462f 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -5137,6 +5137,17 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr)
>  		btrfs_end_write_no_snapshotting(root);
>  		btrfs_end_transaction(trans);
>  	} else {
> +		struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
> +
> +		if (btrfs_fs_incompat(fs_info, HMZONED)) {
> +			u64 sectormask = fs_info->sectorsize - 1;
> +
> +			ret = btrfs_wait_ordered_range(inode,
> +						       newsize & (~sectormask),
> +						       (u64)-1);

Use ALIGN().  Thanks,

Josef