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Wong" To: Chandan Babu R Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH V11 04/14] xfs: Check for extent overflow when adding/removing xattrs Message-ID: <20201209185146.GL1943235@magnolia> References: <20201117134416.207945-1-chandanrlinux@gmail.com> <20201117134416.207945-5-chandanrlinux@gmail.com> <20201203184559.GA106271@magnolia> <4842874.Y7L5Z29mQF@garuda> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4842874.Y7L5Z29mQF@garuda> X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9830 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 spamscore=0 suspectscore=1 bulkscore=0 malwarescore=0 phishscore=0 adultscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012090133 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9830 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=1 adultscore=0 bulkscore=0 phishscore=0 mlxlogscore=999 clxscore=1015 priorityscore=1501 mlxscore=0 spamscore=0 lowpriorityscore=0 malwarescore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012090133 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Fri, Dec 04, 2020 at 02:34:17PM +0530, Chandan Babu R wrote: > On Thu, 03 Dec 2020 10:45:59 -0800, Darrick J. Wong wrote: > > On Tue, Nov 17, 2020 at 07:14:06PM +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. > > > > > > To be able to always remove an existing xattr, when adding an xattr we > > > make sure to reserve inode fork extent count required for removing max > > > sized xattr in addition to that required by the xattr add operation. > > > > > > Signed-off-by: Chandan Babu R > > > --- > > > fs/xfs/libxfs/xfs_attr.c | 20 ++++++++++++++++++++ > > > fs/xfs/libxfs/xfs_inode_fork.h | 10 ++++++++++ > > > 2 files changed, 30 insertions(+) > > > > > > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c > > > index fd8e6418a0d3..d53b3867b308 100644 > > > --- a/fs/xfs/libxfs/xfs_attr.c > > > +++ b/fs/xfs/libxfs/xfs_attr.c > > > @@ -396,6 +396,8 @@ xfs_attr_set( > > > struct xfs_trans_res tres; > > > bool rsvd = (args->attr_filter & XFS_ATTR_ROOT); > > > int error, local; > > > + int iext_cnt; > > > + int rmt_blks; > > > unsigned int total; > > > > > > if (XFS_FORCED_SHUTDOWN(dp->i_mount)) > > > @@ -416,6 +418,9 @@ xfs_attr_set( > > > */ > > > args->op_flags = XFS_DA_OP_OKNOENT; > > > > > > + rmt_blks = xfs_attr3_rmt_blocks(mp, XFS_XATTR_SIZE_MAX); > > > + iext_cnt = XFS_IEXT_ATTR_MANIP_CNT(rmt_blks); > > > > These values are only relevant for the xattr removal case, right? > > AFAICT the args->value != NULL case immediately after will set new > > values, so why not just move this into... > > The above statements compute the extent count required to remove a maximum > sized remote xattr. > > To guarantee that a user can always remove an xattr, the "args->value != NULL" > case adds to the value of iext_cnt that has been computed above. I had > extracted and placed the above set of statements since they were now common to > both "insert" and "remove" xattr operations. D'oh, you're right. > > > > > + > > > if (args->value) { > > > XFS_STATS_INC(mp, xs_attr_set); > > > > > > @@ -442,6 +447,13 @@ 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 = 0; > > > + else > > > + rmt_blks = xfs_attr3_rmt_blocks(mp, args->valuelen); > > > + > > > + iext_cnt += XFS_IEXT_ATTR_MANIP_CNT(rmt_blks); > > > } else { > > > XFS_STATS_INC(mp, xs_attr_remove); > > > > ...the bottom of this clause here. > > > > > > > > @@ -460,6 +472,14 @@ xfs_attr_set( > > > > > > xfs_ilock(dp, XFS_ILOCK_EXCL); > > > xfs_trans_ijoin(args->trans, dp, 0); > > > + > > > + if (args->value || xfs_inode_hasattr(dp)) { > > > > Can this simply be "if (iext_cnt != 0)" ? > > That would lead to a bug since iext_cnt is computed unconditionally at the > beginning of the function. An extent count reservation will be attempted when > xattr delete operation is executed against an inode which does not have an > associated attr fork. This will cause xfs_iext_count_may_overflow() to > dereference the NULL pointer at xfs_inode->i_afp->if_nextents. Ah, right, got it. This looks fine to me then... Reviewed-by: Darrick J. Wong --D > > > > --D > > > > > + error = xfs_iext_count_may_overflow(dp, XFS_ATTR_FORK, > > > + iext_cnt); > > > + 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. > > > */ > > > > > -- > chandan > > >