Re: [PATCH V7 04/14] xfs: Check for extent overflow when adding/removing xattrs

Allison Henderson
2020-10-24T19:29:25Z

On 10/18/20 11:40 PM, Chandan Babu R wrote:
> Adding/removing an xattr can cause XFS_DA_NODE_MAXDEPTH extents to be
> added. One extra extent for dabtree in case a local attr is large enough
> to cause a double split. It can also cause extent count to increase
> proportional to the size of a remote xattr's value.
>
Ok makes sense
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_attr.c | 13 +++++++++++++
> fs/xfs/libxfs/xfs_inode_fork.h | 10 ++++++++++
> 2 files changed, 23 insertions(+)
>
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index fd8e6418a0d3..be51e7068dcd 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -396,6 +396,7 @@ xfs_attr_set(
> struct xfs_trans_res tres;
> bool rsvd = (args->attr_filter & XFS_ATTR_ROOT);
> int error, local;
> + int rmt_blks = 0;
> unsigned int total;
>
> if (XFS_FORCED_SHUTDOWN(dp->i_mount))
> @@ -442,11 +443,15 @@ xfs_attr_set(
> tres.tr_logcount = XFS_ATTRSET_LOG_COUNT;
> tres.tr_logflags = XFS_TRANS_PERM_LOG_RES;
> total = args->total;
> +
> + if (!local)
> + rmt_blks = xfs_attr3_rmt_blocks(mp, args->valuelen);
> } else {
> XFS_STATS_INC(mp, xs_attr_remove);
>
> tres = M_RES(mp)->tr_attrrm;
> total = XFS_ATTRRM_SPACE_RES(mp);
> + rmt_blks = xfs_attr3_rmt_blocks(mp, XFS_XATTR_SIZE_MAX);
> }
>
> /*
> @@ -460,6 +465,14 @@ xfs_attr_set(
>
> xfs_ilock(dp, XFS_ILOCK_EXCL);
> xfs_trans_ijoin(args->trans, dp, 0);
> +
> + if (args->value || xfs_inode_hasattr(dp)) {
> + error = xfs_iext_count_may_overflow(dp, XFS_ATTR_FORK,
> + XFS_IEXT_ATTR_MANIP_CNT(rmt_blks));
> + if (error)
> + goto out_trans_cancel;
> + }
> +
> if (args->value) {
> unsigned int quota_flags = XFS_QMOPT_RES_REGBLKS;
>
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
> index bcac769a7df6..5de2f07d0dd5 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.h
> +++ b/fs/xfs/libxfs/xfs_inode_fork.h
> @@ -47,6 +47,16 @@ struct xfs_ifork {
> */
> #define XFS_IEXT_PUNCH_HOLE_CNT (1)
>
> +/*
> + * Adding/removing an xattr can cause XFS_DA_NODE_MAXDEPTH extents to
> + * be added. One extra extent for dabtree in case a local attr is
> + * large enough to cause a double split. It can also cause extent
> + * count to increase proportional to the size of a remote xattr's
> + * value.
> + */
> +#define XFS_IEXT_ATTR_MANIP_CNT(rmt_blks) \
> + (XFS_DA_NODE_MAXDEPTH + max(1, rmt_blks))
> +
> /*
> * Fork handling.
> */
>