From 84c529aea182939e68f618ed9813740c9165c7eb Mon Sep 17 00:00:00 2001 From: Andrea Righi Date: Wed, 13 Nov 2019 16:03:21 +0800 Subject: [PATCH] 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 Signed-off-by: Coly Li Signed-off-by: Jens Axboe --- drivers/md/bcache/alloc.c | 5 ++++- drivers/md/bcache/bcache.h | 2 +- drivers/md/bcache/super.c | 27 +++++++++++++++++++++------ 3 files changed, 26 insertions(+), 8 deletions(-) diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c index 6f77682..a1df0d9 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 3653faf..50241e0 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 623fdaf..d1352fc 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"; -- 2.7.4