Re: [PATCH V7 03/14] xfs: Check for extent overflow when punching a hole

Allison Henderson
2020-10-24T19:31:07Z

On 10/18/20 11:40 PM, 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.
>
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 | 7 +++++++
> fs/xfs/xfs_bmap_item.c | 15 +++++++++------
> fs/xfs/xfs_bmap_util.c | 10 ++++++++++
> 3 files changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
> index 7fc2b129a2e7..bcac769a7df6 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.h
> +++ b/fs/xfs/libxfs/xfs_inode_fork.h
> @@ -40,6 +40,13 @@ struct xfs_ifork {
> */
> #define XFS_IEXT_ADD_NOSPLIT_CNT (1)
>
> +/*
> + * Punching out an extent from the middle of an existing extent can cause the
> + * extent count to increase by 1.
> + * i.e. | Old extent | Hole | Old extent |
> + */
> +#define XFS_IEXT_PUNCH_HOLE_CNT (1)
> +
> /*
> * Fork handling.
> */
> diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c
> index 1610d6ad089b..80d828394158 100644
> --- a/fs/xfs/xfs_bmap_item.c
> +++ b/fs/xfs/xfs_bmap_item.c
> @@ -439,6 +439,7 @@ xfs_bui_item_recover(
> xfs_exntst_t state;
> unsigned int bui_type;
> int whichfork;
> + int iext_delta;
> int error = 0;
>
> /* Only one mapping operation per BUI... */
> @@ -497,12 +498,14 @@ xfs_bui_item_recover(
> xfs_ilock(ip, XFS_ILOCK_EXCL);
> xfs_trans_ijoin(tp, ip, 0);
>
> - if (bui_type == XFS_BMAP_MAP) {
> - error = xfs_iext_count_may_overflow(ip, whichfork,
> - XFS_IEXT_ADD_NOSPLIT_CNT);
> - if (error)
> - goto err_cancel;
> - }
> + if (bui_type == XFS_BMAP_MAP)
> + iext_delta = XFS_IEXT_ADD_NOSPLIT_CNT;
> + else
> + iext_delta = XFS_IEXT_PUNCH_HOLE_CNT;
> +
> + error = xfs_iext_count_may_overflow(ip, whichfork, iext_delta);
> + if (error)
> + goto err_cancel;
>
> count = bmap->me_len;
> error = xfs_trans_log_finish_bmap_update(tp, budp, bui_type, ip,
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index dcd6e61df711..0776abd0103c 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -891,6 +891,11 @@ xfs_unmap_extent(
>
> xfs_trans_ijoin(tp, ip, 0);
>
> + error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
> + XFS_IEXT_PUNCH_HOLE_CNT);
> + if (error)
> + goto out_trans_cancel;
> +
> error = xfs_bunmapi(tp, ip, startoffset_fsb, len_fsb, 0, 2, done);
> if (error)
> goto out_trans_cancel;
> @@ -1176,6 +1181,11 @@ xfs_insert_file_space(
> xfs_ilock(ip, XFS_ILOCK_EXCL);
> xfs_trans_ijoin(tp, ip, 0);
>
> + error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
> + XFS_IEXT_PUNCH_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
>