Re: [PATCH 2/5] xfs: add flush flag to xfs_eofblocks

[Dave Chinner <david@fromorbit.com>]

On Fri, Mar 28, 2014 at 09:16:00AM -0400, Brian Foster wrote:
> The flush flag allows the caller to issue a flush for scanned inodes. In
> ENOSPC conditions caused by project quotas, a flush is required to free
> up reserved metadata allocations.
> 
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
>  fs/xfs/xfs_fs.h     | 4 +++-
>  fs/xfs/xfs_icache.c | 3 +++
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_fs.h b/fs/xfs/xfs_fs.h
> index c5fc116..fa3a58e 100644
> --- a/fs/xfs/xfs_fs.h
> +++ b/fs/xfs/xfs_fs.h
> @@ -374,12 +374,14 @@ struct xfs_fs_eofblocks {
>  #define XFS_EOF_FLAGS_GID		(1 << 2) /* filter by gid */
>  #define XFS_EOF_FLAGS_PRID		(1 << 3) /* filter by project id */
>  #define XFS_EOF_FLAGS_MINFILESIZE	(1 << 4) /* filter by min file size */
> +#define XFS_EOF_FLAGS_FLUSH		(1 << 5) /* issue a flush */
>  #define XFS_EOF_FLAGS_VALID	\
>  	(XFS_EOF_FLAGS_SYNC |	\
>  	 XFS_EOF_FLAGS_UID |	\
>  	 XFS_EOF_FLAGS_GID |	\
>  	 XFS_EOF_FLAGS_PRID |	\
> -	 XFS_EOF_FLAGS_MINFILESIZE)
> +	 XFS_EOF_FLAGS_MINFILESIZE | \
> +	 XFS_EOF_FLAGS_FLUSH)
>  
>  
>  /*
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index 7ff59c9..d4e15db 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -1231,6 +1231,9 @@ xfs_inode_free_eofblocks(
>  		if (eofb->eof_flags & XFS_EOF_FLAGS_MINFILESIZE &&
>  		    XFS_ISIZE(ip) < eofb->eof_min_file_size)
>  			return 0;
> +
> +		if (eofb->eof_flags & XFS_EOF_FLAGS_FLUSH)
> +			filemap_flush(VFS_I(ip)->i_mapping);

So this does WB_SYNC_NONE writeback, which means the filesystem is
free to ignore it when we get to .writepage. Given that we are are
ENOSPC here, wouldn't it be better to guarantee that writeback will
occur (i.e. use filemap_fdatawrite())?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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