From: Jie Liu <jeff.liu@xxxxxxxxxx>
xfs_quota(8) will hang up if trying to turn group quota or project
quota before the user quota is off, this could be 100% reproduced by:
# mount -ouquota,gquota /dev/sda7 /xfs
# mkdir /xfs/test
# xfs_quota -xc 'off -g' /xfs
# echo w > /proc/sysrq-trigger
SysRq : Show Blocked State
task PC stack pid father
xfs_quota D 0000000000000000 0 27574 2551 0x00000000
[snip]
Call Trace:
[<ffffffff81aaa21d>] schedule+0xad/0xc0
[<ffffffff81aa327e>] schedule_timeout+0x35e/0x3c0
[<ffffffff8114b506>] ? mark_held_locks+0x176/0x1c0
[<ffffffff810ad6c0>] ? call_timer_fn+0x2c0/0x2c0
[<ffffffffa0c25380>] ? xfs_qm_shrink_count+0x30/0x30 [xfs]
[<ffffffff81aa3306>] schedule_timeout_uninterruptible+0x26/0x30
[<ffffffffa0c26155>] xfs_qm_dquot_walk+0x235/0x260 [xfs]
[<ffffffffa0c059d8>] ? xfs_perag_get+0x1d8/0x2d0 [xfs]
[<ffffffffa0c05805>] ? xfs_perag_get+0x5/0x2d0 [xfs]
[<ffffffffa0b7707e>] ? xfs_inode_ag_iterator+0xae/0xf0 [xfs]
[<ffffffffa0c22280>] ? xfs_trans_free_dqinfo+0x50/0x50 [xfs]
[<ffffffffa0b7709f>] ? xfs_inode_ag_iterator+0xcf/0xf0 [xfs]
[<ffffffffa0c261e6>] xfs_qm_dqpurge_all+0x66/0xb0 [xfs]
[<ffffffffa0c2497a>] xfs_qm_scall_quotaoff+0x20a/0x5f0 [xfs]
[<ffffffffa0c2b8f6>] xfs_fs_set_xstate+0x136/0x180 [xfs]
[<ffffffff8136cf7a>] do_quotactl+0x53a/0x6b0
[<ffffffff812fba4b>] ? iput+0x5b/0x90
[<ffffffff8136d257>] SyS_quotactl+0x167/0x1d0
[<ffffffff814cf2ee>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[<ffffffff81abcd19>] system_call_fastpath+0x16/0x1b
It's fine if we turn user quota off at first, then turn off other
kind of quotas if they are enabled since the group/project dquot
refcount is decreased to zero once the user quota if off. Otherwse,
those dquots refcount is non-zero due to the user dquot maybe refer
to them as hint(s). Hence, above operation hit an infinite loop at
xfs_qm_dquot_walk() to purge dquot cache.
This problem has been around since Linux 3.4, it was introduced by:
b84a3a96751f93071c1863f2962273973c8b8f5e
xfs: remove the per-filesystem list of dquots
Originally we will release the group dquot pointers because the user
dquots maybe carrying around as a hint via xfs_qm_detach_gdquots().
However, with this change, there is no such work to be done before
purge group/project dquot cache.
This fix introduce a similar routine to the old xfs_qm_detach_gdquots(),
it will detach the group/project hints by searching the user dquot radix
tree and release those hints if they are there.
Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
---
fs/xfs/xfs_qm.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 77 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index 14a4996..410adf4 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -60,6 +60,77 @@ STATIC void xfs_qm_dqfree_one(struct xfs_dquot *dqp);
*/
#define XFS_DQ_LOOKUP_BATCH 32
+/*
+ * Release the group or project dquot pointers the user dquots may be
+ * carrying around as a hint.
+ */
+STATIC void
+xfs_qm_dqdetach_hint(
+ struct xfs_mount *mp,
+ int type)
+{
+ struct xfs_quotainfo *qi = mp->m_quotainfo;
+ struct radix_tree_root *tree = xfs_dquot_tree(qi, XFS_DQ_USER);
+ uint32_t next_index;
+ int skipped;
+ int nr_found;
+
+ ASSERT(type == XFS_DQ_GROUP || type == XFS_DQ_PROJ);
+
+restart:
+ next_index = 0;
+ skipped = 0;
+ nr_found = 0;
+
+ while (1) {
+ struct xfs_dquot *batch[XFS_DQ_LOOKUP_BATCH];
+ int i;
+
+ mutex_lock(&qi->qi_tree_lock);
+ nr_found = radix_tree_gang_lookup(tree, (void **)batch,
+ next_index, XFS_DQ_LOOKUP_BATCH);
+ if (!nr_found) {
+ mutex_unlock(&qi->qi_tree_lock);
+ break;
+ }
+
+ for (i = 0; i < nr_found; i++) {
+ struct xfs_dquot *dqp = batch[i];
+ struct xfs_dquot *dqhintp;
+
+ next_index = be32_to_cpu(dqp->q_core.d_id) + 1;
+
+ xfs_dqlock(dqp);
+ if (dqp->dq_flags & XFS_DQ_FREEING) {
+ xfs_dqunlock(dqp);
+ skipped++;
+ continue;
+ }
+
+ if (type == XFS_DQ_GROUP) {
+ dqhintp = dqp->q_gdquot;
+ if (dqhintp)
+ dqp->q_gdquot = NULL;
+ } else {
+ dqhintp = dqp->q_pdquot;
+ if (dqhintp)
+ dqp->q_pdquot = NULL;
+ }
+ xfs_dqunlock(dqp);
+
+ if (dqhintp)
+ xfs_qm_dqrele(dqhintp);
+ }
+
+ mutex_unlock(&qi->qi_tree_lock);
+ }
+
+ if (skipped) {
+ delay(1);
+ goto restart;
+ }
+}
+
STATIC int
xfs_qm_dquot_walk(
struct xfs_mount *mp,
@@ -224,10 +295,14 @@ xfs_qm_dqpurge_all(
{
if (flags & XFS_QMOPT_UQUOTA)
xfs_qm_dquot_walk(mp, XFS_DQ_USER, xfs_qm_dqpurge, NULL);
- if (flags & XFS_QMOPT_GQUOTA)
+ if (flags & XFS_QMOPT_GQUOTA) {
+ xfs_qm_dqdetach_hint(mp, XFS_DQ_GROUP);
xfs_qm_dquot_walk(mp, XFS_DQ_GROUP, xfs_qm_dqpurge, NULL);
- if (flags & XFS_QMOPT_PQUOTA)
+ }
+ if (flags & XFS_QMOPT_PQUOTA) {
+ xfs_qm_dqdetach_hint(mp, XFS_DQ_PROJ);
xfs_qm_dquot_walk(mp, XFS_DQ_PROJ, xfs_qm_dqpurge, NULL);
+ }
}
/*
--
1.7.9.5
_______________________________________________
xfs mailing list
xfs@xxxxxxxxxxx
http://oss.sgi.com/mailman/listinfo/xfs
