Hello Yan, Zheng,
The patch 5dda377cf0a6: "ceph: set i_head_snapc when getting
CEPH_CAP_FILE_WR reference" from Apr 30, 2015, leads to the following
static checker warning:
fs/ceph/snap.c:557 ceph_queue_cap_snap()
error: potential NULL dereference 'old_snapc'.
fs/ceph/snap.c
547 /* dirty page count moved from _head to this cap_snap;
548 all subsequent writes page dirties occur _after_ this
549 snapshot. */
550 capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
551 ci->i_wrbuffer_ref_head = 0;
552 capsnap->context = old_snapc;
553 list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);
554 old_snapc = NULL;
^^^^^^^^^^^^^^^^^
555
556 if (used & CEPH_CAP_FILE_WR) {
557 dout("queue_cap_snap %p cap_snap %p snapc %p"
558 " seq %llu used WR, now pending\n", inode,
559 capsnap, old_snapc, old_snapc->seq);
^^^^^^^^^^^^^^
This is a NULL deref.
560 capsnap->writing = 1;
561 } else {
562 /* note mtime, size NOW. */
563 __ceph_finish_cap_snap(ci, capsnap);
564 }
565 capsnap = NULL;
regards,
dan carpenter
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