leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

bcache: fix deadlock in bcache_allocator

Browse Source 
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>
This commit is contained in:
Andrea Righi 2019-11-13 16:03:21 +08:00 committed by Jens Axboe
parent 06c1526da9
commit 84c529aea1
3 changed files with 26 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
drivers/md/bcache/alloc.c
View File

@ -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:

2
drivers/md/bcache/bcache.h
View File

@ -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;

27
drivers/md/bcache/super.c
View File

@ -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";