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authorColy Li <colyli@suse.de>2020-02-13 22:12:05 +0800
committerJens Axboe <axboe@kernel.dk>2020-02-13 08:53:49 -0700
commit0b96da639a4874311e9b5156405f69ef9fc3bef8 (patch)
tree4ae8a61d60b114f9a5b49973aa8dc1f76003e4d9
parentb74e58cd472cb782d34ecfad553c12c66eb02b6b (diff)
downloadlwn-0b96da639a4874311e9b5156405f69ef9fc3bef8.tar.gz
lwn-0b96da639a4874311e9b5156405f69ef9fc3bef8.zip
bcache: ignore pending signals when creating gc and allocator thread
When run a cache set, all the bcache btree node of this cache set will be checked by bch_btree_check(). If the bcache btree is very large, iterating all the btree nodes will occupy too much system memory and the bcache registering process might be selected and killed by system OOM killer. kthread_run() will fail if current process has pending signal, therefore the kthread creating in run_cache_set() for gc and allocator kernel threads are very probably failed for a very large bcache btree. Indeed such OOM is safe and the registering process will exit after the registration done. Therefore this patch flushes pending signals during the cache set start up, specificly in bch_cache_allocator_start() and bch_gc_thread_start(), to make sure run_cache_set() won't fail for large cahced data set. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--drivers/md/bcache/alloc.c18
-rw-r--r--drivers/md/bcache/btree.c13
2 files changed, 29 insertions, 2 deletions
diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index a1df0d95151c..8bc1faf71ff2 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -67,6 +67,7 @@
#include <linux/blkdev.h>
#include <linux/kthread.h>
#include <linux/random.h>
+#include <linux/sched/signal.h>
#include <trace/events/bcache.h>
#define MAX_OPEN_BUCKETS 128
@@ -733,8 +734,21 @@ int bch_open_buckets_alloc(struct cache_set *c)
int bch_cache_allocator_start(struct cache *ca)
{
- struct task_struct *k = kthread_run(bch_allocator_thread,
- ca, "bcache_allocator");
+ struct task_struct *k;
+
+ /*
+ * In case previous btree check operation occupies too many
+ * system memory for bcache btree node cache, and the
+ * registering process is selected by OOM killer. Here just
+ * ignore the SIGKILL sent by OOM killer if there is, to
+ * avoid kthread_run() being failed by pending signals. The
+ * bcache registering process will exit after the registration
+ * done.
+ */
+ if (signal_pending(current))
+ flush_signals(current);
+
+ k = kthread_run(bch_allocator_thread, ca, "bcache_allocator");
if (IS_ERR(k))
return PTR_ERR(k);
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index fa872df4e770..b12186c87f52 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -34,6 +34,7 @@
#include <linux/random.h>
#include <linux/rcupdate.h>
#include <linux/sched/clock.h>
+#include <linux/sched/signal.h>
#include <linux/rculist.h>
#include <linux/delay.h>
#include <trace/events/bcache.h>
@@ -1913,6 +1914,18 @@ static int bch_gc_thread(void *arg)
int bch_gc_thread_start(struct cache_set *c)
{
+ /*
+ * In case previous btree check operation occupies too many
+ * system memory for bcache btree node cache, and the
+ * registering process is selected by OOM killer. Here just
+ * ignore the SIGKILL sent by OOM killer if there is, to
+ * avoid kthread_run() being failed by pending signals. The
+ * bcache registering process will exit after the registration
+ * done.
+ */
+ if (signal_pending(current))
+ flush_signals(current);
+
c->gc_thread = kthread_run(bch_gc_thread, c, "bcache_gc");
return PTR_ERR_OR_ZERO(c->gc_thread);
}