Re: [PATCH V7 06/14] xfs: Check for extent overflow when writing to unwritten extent

Allison Henderson
2020-10-24T20:19:06Z

On 10/18/20 11:40 PM, Chandan Babu R wrote:
> A write to a sub-interval of an existing unwritten extent causes
> the original extent to be split into 3 extents
> i.e. | Unwritten | Real | Unwritten |
> Hence extent count can increase by 2.
>
Looks good
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
> ---
> fs/xfs/libxfs/xfs_inode_fork.h | 8 ++++++++
> fs/xfs/xfs_iomap.c | 5 +++++
> 2 files changed, 13 insertions(+)
>
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
> index fd93fdc67ee4..afb647e1e3fa 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.h
> +++ b/fs/xfs/libxfs/xfs_inode_fork.h
> @@ -70,6 +70,14 @@ struct xfs_ifork {
> #define XFS_IEXT_DIR_MANIP_CNT(mp) \
> ((XFS_DA_NODE_MAXDEPTH + 1 + 1) * (mp)->m_dir_geo->fsbcount)
>
> +/*
> + * A write to a sub-interval of an existing unwritten extent causes the original
> + * extent to be split into 3 extents
> + * i.e. | Unwritten | Real | Unwritten |
> + * Hence extent count can increase by 2.
> + */
> +#define XFS_IEXT_WRITE_UNWRITTEN_CNT (2)
> +
> /*
> * Fork handling.
> */
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index a302a96823b8..2aa788379611 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -566,6 +566,11 @@ xfs_iomap_write_unwritten(
> if (error)
> goto error_on_bmapi_transaction;
>
> + error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
> + XFS_IEXT_WRITE_UNWRITTEN_CNT);
> + if (error)
> + goto error_on_bmapi_transaction;
> +
> /*
> * Modify the unwritten extent state of the buffer.
> */
>