ploop_check_delta_before_flip() locks the live device's md->md_lock and
then a second md_lock from the delta being read into a separate md_root
tree (d_md). They are distinct objects of the same lock class, so lockdep
reports a false "possible recursive locking" deadlock. The two are only
ever taken here and always in this (md, then d_md) order, so annotate the
inner acquire with SINGLE_DEPTH_NESTING.
Fixes: a9cd5e6dc646 ("dm-ploop: Add ploop target driver")
Feature: dm-ploop: ploop target driver
https://virtuozzo.atlassian.net/browse/VSTOR-137234
Signed-off-by: Konstantin Khorenko <[email protected]>
---
drivers/md/dm-ploop-cmd.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm-ploop-cmd.c b/drivers/md/dm-ploop-cmd.c
index 5fa78e6cff9a..73c5613c82f5 100644
--- a/drivers/md/dm-ploop-cmd.c
+++ b/drivers/md/dm-ploop-cmd.c
@@ -1101,7 +1101,13 @@ static int ploop_check_delta_before_flip(struct ploop
*ploop, struct file *file)
d_bat_entries = d_md->kmpage;
spin_lock_irq(&md->md_lock); /* read */
- spin_lock(&d_md->md_lock);
+ /*
+ * md (live device tree) and d_md (delta being read into a
+ * separate md_root tree) are distinct md_page objects of the
+ * same lock class; they are only ever locked here in this
+ * order, so annotate the nesting for lockdep.
+ */
+ spin_lock_nested(&d_md->md_lock, SINGLE_DEPTH_NESTING);
for (; i <= end; i++) {
if (ploop_md_page_cluster_is_in_top_delta(ploop, md, i)
&&
d_bat_entries[i] != BAT_ENTRY_NONE) {
--
2.47.1
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