[PATCH v2 1/2] gfs2: fix quota init duplicate scan

Jie Wang
2026-04-21T08:44:50Z

gfs2_quota_init() checks for duplicate quota_change IDs while holding
qd_lock and the quota hash bucket bitlock. That path used
gfs2_qd_search_bucket(), which takes a lockref reference via
lockref_get_not_dead().

On PREEMPT_RT this may sleep, which is not allowed under the bucket
bitlock, triggering "sleeping function called from invalid context".

Use a no-ref bucket lookup in this path, then continue duplicate
handling without taking a lockref there.

Refactor gfs2_qd_search_bucket() to build on top of the no-ref helper
so lookup traversal stays in one place.

This patch fixes a bug reported by syzbot.

Reported-by: syzbot+642d0561f78362d67d3f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=642d0561f78362d67d3f
Tested-by: syzbot+642d0561f78362d67d3f@syzkaller.appspotmail.com
Signed-off-by: Jie Wang <jie.wang@intel.com>
---
fs/gfs2/quota.c | 36 +++++++++++++++++++++++++-----------
1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index 5290865f27f1..df1cb99c3344 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -254,9 +254,13 @@ static struct gfs2_quota_data *qd_alloc(unsigned hash, struct gfs2_sbd *sdp, str
return NULL;
}

-static struct gfs2_quota_data *gfs2_qd_search_bucket(unsigned int hash,
- const struct gfs2_sbd *sdp,
- struct kqid qid)
+/*
+ * Lookup variant for callers which already hold qd_lock + bucket lock.
+ */
+static struct gfs2_quota_data *
+gfs2_qd_search_bucket_noref(unsigned int hash,
+ const struct gfs2_sbd *sdp,
+ struct kqid qid)
{
struct gfs2_quota_data *qd;
struct hlist_bl_node *h;
@@ -264,12 +268,22 @@ static struct gfs2_quota_data *gfs2_qd_search_bucket(unsigned int hash,
hlist_bl_for_each_entry_rcu(qd, h, &qd_hash_table[hash], qd_hlist) {
if (!qid_eq(qd->qd_id, qid))
continue;
- if (qd->qd_sbd != sdp)
- continue;
- if (lockref_get_not_dead(&qd->qd_lockref)) {
- list_lru_del_obj(&gfs2_qd_lru, &qd->qd_lru);
+ if (qd->qd_sbd == sdp)
return qd;
- }
+ }
+
+ return NULL;
+}
+
+static struct gfs2_quota_data *
+gfs2_qd_search_bucket(unsigned int hash, const struct gfs2_sbd *sdp, struct kqid qid)
+{
+ struct gfs2_quota_data *qd;
+
+ qd = gfs2_qd_search_bucket_noref(hash, sdp, qid);
+ if (qd && lockref_get_not_dead(&qd->qd_lockref)) {
+ list_lru_del_obj(&gfs2_qd_lru, &qd->qd_lru);
+ return qd;
}

return NULL;
@@ -1458,16 +1472,15 @@ int gfs2_quota_init(struct gfs2_sbd *sdp)

spin_lock(&qd_lock);
spin_lock_bucket(hash);
- old_qd = gfs2_qd_search_bucket(hash, sdp, qc_id);
+ old_qd = gfs2_qd_search_bucket_noref(hash, sdp, qc_id);
+ spin_unlock_bucket(hash);
if (old_qd) {
fs_err(sdp, "Corruption found in quota_change%u"
"file: duplicate identifier in "
"slot %u\n",
sdp->sd_jdesc->jd_jid, slot);

- spin_unlock_bucket(hash);
spin_unlock(&qd_lock);
- qd_put(old_qd);

gfs2_glock_put(qd->qd_gl);
kmem_cache_free(gfs2_quotad_cachep, qd);
@@ -1483,6 +1496,7 @@ int gfs2_quota_init(struct gfs2_sbd *sdp)
BUG_ON(test_and_set_bit(slot, sdp->sd_quota_bitmap));
list_add(&qd->qd_list, &sdp->sd_quota_list);
atomic_inc(&sdp->sd_quota_count);
+ spin_lock_bucket(hash);
hlist_bl_add_head_rcu(&qd->qd_hlist, &qd_hash_table[hash]);
spin_unlock_bucket(hash);
spin_unlock(&qd_lock);
--
2.34.1