[PATCH v2] bcache: fixup btree_cache_wait list damage

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



We get a kernel crash about "list_add corruption. next->prev should be
prev (ffff9c801bc01210), but was ffff9c77b688237c. (next=ffffae586d8afe68)."

crash> struct list_head 0xffff9c801bc01210
struct list_head {
  next = 0xffffae586d8afe68,
  prev = 0xffffae586d8afe68
}
crash> struct list_head 0xffff9c77b688237c
struct list_head {
  next = 0x0,
  prev = 0x0
}
crash> struct list_head 0xffffae586d8afe68
struct list_head struct: invalid kernel virtual address: ffffae586d8afe68  type: "gdb_readmem_callback"
Cannot access memory at address 0xffffae586d8afe68

[230469.019492] Call Trace:
[230469.032041]  prepare_to_wait+0x8a/0xb0
[230469.044363]  ? bch_btree_keys_free+0x6c/0xc0 [bcache]
[230469.056533]  mca_cannibalize_lock+0x72/0x90 [bcache]
[230469.068788]  mca_alloc+0x2ae/0x450 [bcache]
[230469.080790]  bch_btree_node_get+0x136/0x2d0 [bcache]
[230469.092681]  bch_btree_check_thread+0x1e1/0x260 [bcache]
[230469.104382]  ? finish_wait+0x80/0x80
[230469.115884]  ? bch_btree_check_recurse+0x1a0/0x1a0 [bcache]
[230469.127259]  kthread+0x112/0x130
[230469.138448]  ? kthread_flush_work_fn+0x10/0x10
[230469.149477]  ret_from_fork+0x35/0x40

bch_btree_check_thread() and bch_dirty_init_thread() maybe call
mca_cannibalize() to cannibalize other cached btree nodes. Only
one thread can do it at a time, so the op of other threads will
be added to the btree_cache_wait list.

We must call finish_wait() to remove op from btree_cache_wait
before free it's memory address. Otherwise, the list will be
damaged. Also should call bch_cannibalize_unlock() to release
the btree_cache_alloc_lock and wake_up other waiters.

Signed-off-by: Mingzhe Zou <mingzhe.zou@xxxxxxxxxxxx>

---
Changelog:
v2: apply to 6.3-rc4.
v1: Original verison.
---
 drivers/md/bcache/btree.c     | 10 +++++++++-
 drivers/md/bcache/btree.h     |  2 ++
 drivers/md/bcache/writeback.c |  8 ++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 147c493a989a..d53483cbd378 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -885,7 +885,7 @@ static struct btree *mca_cannibalize(struct cache_set *c, struct btree_op *op,
  * cannibalize_bucket() will take. This means every time we unlock the root of
  * the btree, we need to release this lock if we have it held.
  */
-static void bch_cannibalize_unlock(struct cache_set *c)
+void bch_cannibalize_unlock(struct cache_set *c)
 {
 	spin_lock(&c->btree_cannibalize_lock);
 	if (c->btree_cache_alloc_lock == current) {
@@ -1968,6 +1968,14 @@ static int bch_btree_check_thread(void *arg)
 			c->gc_stats.nodes++;
 			bch_btree_op_init(&op, 0);
 			ret = bcache_btree(check_recurse, p, c->root, &op);
+			/* The op may be added to cache_set's btree_cache_wait
+			* in mca_cannibalize(), must ensure it is removed from
+			* the list and release btree_cache_alloc_lock before
+			* free op memory.
+			* Otherwise, the btree_cache_wait will be damaged.
+			*/
+			bch_cannibalize_unlock(c);
+			finish_wait(&c->btree_cache_wait, &(&op)->wait);
 			if (ret)
 				goto out;
 		}
diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
index 1b5fdbc0d83e..5a3c602c2929 100644
--- a/drivers/md/bcache/btree.h
+++ b/drivers/md/bcache/btree.h
@@ -365,6 +365,8 @@ static inline void force_wake_up_gc(struct cache_set *c)
 	_r;                                                             \
 })
 
+void bch_cannibalize_unlock(struct cache_set *c);
+
 #define MAP_DONE	0
 #define MAP_CONTINUE	1
 
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index d4a5fc0650bb..ebc1f65727ea 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -890,6 +890,14 @@ static int bch_root_node_dirty_init(struct cache_set *c,
 	if (ret < 0)
 		pr_warn("sectors dirty init failed, ret=%d!\n", ret);
 
+	/* The op may be added to cache_set's btree_cache_wait
+	 * in mca_cannibalize(), must ensure it is removed from
+	 * the list and release btree_cache_alloc_lock before
+	 * free op memory.
+	 * Otherwise, the btree_cache_wait will be damaged.
+	 */
+	bch_cannibalize_unlock(c);
+	finish_wait(&c->btree_cache_wait, &(&op.op)->wait);
 	return ret;
 }
 
-- 
2.17.1.windows.2




[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Linux ARM Kernel]     [Linux Filesystem Development]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Security]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [ECOS]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux