Re: [PATCH V3 07/10] xfs: Check for extent overflow when inserting a hole

Darrick J. Wong
2020-08-31T16:48:44Z

On Thu, Aug 20, 2020 at 11:13:46AM +0530, Chandan Babu R wrote:
> The extent mapping the file offset at which a hole has to be
> inserted will be split into two extents causing extent count to
> increase by 1.
>
> Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
> ---
> fs/xfs/libxfs/xfs_inode_fork.h | 6 ++++++
> fs/xfs/xfs_bmap_util.c | 9 +++++++++
> 2 files changed, 15 insertions(+)
>
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
> index 83ff90e2a5fe..d0e49b015b62 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.h
> +++ b/fs/xfs/libxfs/xfs_inode_fork.h
> @@ -73,6 +73,12 @@ struct xfs_ifork {
> * Hence extent count can increase by 2.
> */
> #define XFS_IEXT_WRITE_UNWRITTEN_CNT (2)
> +/*
> + * The extent mapping the file offset at which a hole has to be inserted will be
> + * split into two extents causing extent count to increase by 1.
> + */
> +#define XFS_IEXT_INSERT_HOLE_CNT (1)

Given my earlier comments about how patch 3 is really only testing the
hole punching case, maybe it should be folded into this one? They're
both inserting holes in the extent map.

Otherwise this patch looks good to me.

--D

> +
>
> /*
> * Fork handling.
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 59d4da38aadf..e682eecebb1f 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -1165,6 +1165,15 @@ xfs_insert_file_space(
> xfs_ilock(ip, XFS_ILOCK_EXCL);
> xfs_trans_ijoin(tp, ip, 0);
>
> + /*
> + * Splitting the extent mapping containing stop_fsb will cause
> + * extent count to increase by 1.
> + */
> + error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
> + XFS_IEXT_INSERT_HOLE_CNT);
> + if (error)
> + goto out_trans_cancel;
> +
> /*
> * The extent shifting code works on extent granularity. So, if stop_fsb
> * is not the starting block of extent, we need to split the extent at
> --
> 2.28.0
>