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authorAndrea Righi <andrea.righi@canonical.com>2019-11-13 16:03:21 +0800
committerJens Axboe <axboe@kernel.dk>2019-11-13 15:42:50 -0700
commit84c529aea182939e68f618ed9813740c9165c7eb (patch)
treec78c0dac4b48524af17fae7db7ec90cdcad5645c
parent06c1526da97dd0022973de3fc41b79b2d431b435 (diff)
downloadlinux-84c529aea182939e68f618ed9813740c9165c7eb.tar.bz2
bcache: fix deadlock in bcache_allocator
bcache_allocator can call the following: bch_allocator_thread() -> bch_prio_write() -> bch_bucket_alloc() -> wait on &ca->set->bucket_wait But the wake up event on bucket_wait is supposed to come from bch_allocator_thread() itself => deadlock: [ 1158.490744] INFO: task bcache_allocato:15861 blocked for more than 10 seconds. [ 1158.495929] Not tainted 5.3.0-050300rc3-generic #201908042232 [ 1158.500653] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 1158.504413] bcache_allocato D 0 15861 2 0x80004000 [ 1158.504419] Call Trace: [ 1158.504429] __schedule+0x2a8/0x670 [ 1158.504432] schedule+0x2d/0x90 [ 1158.504448] bch_bucket_alloc+0xe5/0x370 [bcache] [ 1158.504453] ? wait_woken+0x80/0x80 [ 1158.504466] bch_prio_write+0x1dc/0x390 [bcache] [ 1158.504476] bch_allocator_thread+0x233/0x490 [bcache] [ 1158.504491] kthread+0x121/0x140 [ 1158.504503] ? invalidate_buckets+0x890/0x890 [bcache] [ 1158.504506] ? kthread_park+0xb0/0xb0 [ 1158.504510] ret_from_fork+0x35/0x40 Fix by making the call to bch_prio_write() non-blocking, so that bch_allocator_thread() never waits on itself. Moreover, make sure to wake up the garbage collector thread when bch_prio_write() is failing to allocate buckets. BugLink: https://bugs.launchpad.net/bugs/1784665 BugLink: https://bugs.launchpad.net/bugs/1796292 Signed-off-by: Andrea Righi <andrea.righi@canonical.com> Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--drivers/md/bcache/alloc.c5
-rw-r--r--drivers/md/bcache/bcache.h2
-rw-r--r--drivers/md/bcache/super.c27
3 files changed, 26 insertions, 8 deletions
diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index 6f776823b9ba..a1df0d95151c 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -377,7 +377,10 @@ retry_invalidate:
if (!fifo_full(&ca->free_inc))
goto retry_invalidate;
- bch_prio_write(ca);
+ if (bch_prio_write(ca, false) < 0) {
+ ca->invalidate_needs_gc = 1;
+ wake_up_gc(ca->set);
+ }
}
}
out:
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 3653faf3bf48..50241e045c70 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -978,7 +978,7 @@ bool bch_cached_dev_error(struct cached_dev *dc);
__printf(2, 3)
bool bch_cache_set_error(struct cache_set *c, const char *fmt, ...);
-void bch_prio_write(struct cache *ca);
+int bch_prio_write(struct cache *ca, bool wait);
void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent);
extern struct workqueue_struct *bcache_wq;
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 623fdaf10c4c..d1352fcc6ff2 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -530,12 +530,29 @@ static void prio_io(struct cache *ca, uint64_t bucket, int op,
closure_sync(cl);
}
-void bch_prio_write(struct cache *ca)
+int bch_prio_write(struct cache *ca, bool wait)
{
int i;
struct bucket *b;
struct closure cl;
+ pr_debug("free_prio=%zu, free_none=%zu, free_inc=%zu",
+ fifo_used(&ca->free[RESERVE_PRIO]),
+ fifo_used(&ca->free[RESERVE_NONE]),
+ fifo_used(&ca->free_inc));
+
+ /*
+ * Pre-check if there are enough free buckets. In the non-blocking
+ * scenario it's better to fail early rather than starting to allocate
+ * buckets and do a cleanup later in case of failure.
+ */
+ if (!wait) {
+ size_t avail = fifo_used(&ca->free[RESERVE_PRIO]) +
+ fifo_used(&ca->free[RESERVE_NONE]);
+ if (prio_buckets(ca) > avail)
+ return -ENOMEM;
+ }
+
closure_init_stack(&cl);
lockdep_assert_held(&ca->set->bucket_lock);
@@ -545,9 +562,6 @@ void bch_prio_write(struct cache *ca)
atomic_long_add(ca->sb.bucket_size * prio_buckets(ca),
&ca->meta_sectors_written);
- //pr_debug("free %zu, free_inc %zu, unused %zu", fifo_used(&ca->free),
- // fifo_used(&ca->free_inc), fifo_used(&ca->unused));
-
for (i = prio_buckets(ca) - 1; i >= 0; --i) {
long bucket;
struct prio_set *p = ca->disk_buckets;
@@ -565,7 +579,7 @@ void bch_prio_write(struct cache *ca)
p->magic = pset_magic(&ca->sb);
p->csum = bch_crc64(&p->magic, bucket_bytes(ca) - 8);
- bucket = bch_bucket_alloc(ca, RESERVE_PRIO, true);
+ bucket = bch_bucket_alloc(ca, RESERVE_PRIO, wait);
BUG_ON(bucket == -1);
mutex_unlock(&ca->set->bucket_lock);
@@ -594,6 +608,7 @@ void bch_prio_write(struct cache *ca)
ca->prio_last_buckets[i] = ca->prio_buckets[i];
}
+ return 0;
}
static void prio_read(struct cache *ca, uint64_t bucket)
@@ -1964,7 +1979,7 @@ static int run_cache_set(struct cache_set *c)
mutex_lock(&c->bucket_lock);
for_each_cache(ca, c, i)
- bch_prio_write(ca);
+ bch_prio_write(ca, true);
mutex_unlock(&c->bucket_lock);
err = "cannot allocate new UUID bucket";