On Tuesday 6 October 2020 9:53:29 AM IST Darrick J. Wong wrote:
> On Sat, Oct 03, 2020 at 11:26:25AM +0530, 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.
> >
> > Signed-off-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
>
> Didn't I already review this? AFAICT it hasn't changed much, but did
> something change enough to warrant dropping the old RVB tag?
Yes, you had reviewed it earlier. Sorry, I missed out on adding the RVB before
sending the patch.
>
> > ---
> > 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;
>
> Hmm. If you hit this while trying to remove an xattr, what then?
> I suppose you really don't want to overflow naextents, but I suppose the
> only other option is to delete the file. Oh well, attr forks with 65533
> extents should be vanishingly rare, right? Right? :)
Yes, Deleting the corresponding file would be the only option. If we did allow
this operation to succeed we would end up having a silent corruption of the
attr extent counter.
>
> Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> --D
>
> > + }
> > +
> > 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.
> > */
>
--
chandan
