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authorMikulas Patocka <mpatocka@redhat.com>2021-02-10 23:26:23 +0300
committerMike Snitzer <snitzer@redhat.com>2021-02-11 17:45:28 +0300
commita666e5c05e7c4aaabb2c5d58117b0946803d03d2 (patch)
tree1a9dc24b70359cd4f268966d99763d79bea28926 /drivers/md
parente3290b9491ff5b7ee40f9e0a4c06821988a2a2bf (diff)
downloadlinux-a666e5c05e7c4aaabb2c5d58117b0946803d03d2.tar.xz
dm: fix deadlock when swapping to encrypted device
The system would deadlock when swapping to a dm-crypt device. The reason is that for each incoming write bio, dm-crypt allocates memory that holds encrypted data. These excessive allocations exhaust all the memory and the result is either deadlock or OOM trigger. This patch limits the number of in-flight swap bios, so that the memory consumed by dm-crypt is limited. The limit is enforced if the target set the "limit_swap_bios" variable and if the bio has REQ_SWAP set. Non-swap bios are not affected becuase taking the semaphore would cause performance degradation. This is similar to request-based drivers - they will also block when the number of requests is over the limit. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-core.h4
-rw-r--r--drivers/md/dm-crypt.c1
-rw-r--r--drivers/md/dm.c60
3 files changed, 65 insertions, 0 deletions
diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index bf3e66f39a4a..5953ff2bd260 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -103,6 +103,10 @@ struct mapped_device {
/* kobject and completion */
struct dm_kobject_holder kobj_holder;
+ int swap_bios;
+ struct semaphore swap_bios_semaphore;
+ struct mutex swap_bios_lock;
+
struct dm_stats stats;
/* for blk-mq request-based DM support */
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index ae0f0a4e3689..11c105ecd165 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -3342,6 +3342,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
wake_up_process(cc->write_thread);
ti->num_flush_bios = 1;
+ ti->limit_swap_bios = true;
return 0;
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7021aea82aa4..50b693d776d6 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -153,6 +153,16 @@ EXPORT_SYMBOL_GPL(dm_bio_get_target_bio_nr);
#define DM_NUMA_NODE NUMA_NO_NODE
static int dm_numa_node = DM_NUMA_NODE;
+#define DEFAULT_SWAP_BIOS (8 * 1048576 / PAGE_SIZE)
+static int swap_bios = DEFAULT_SWAP_BIOS;
+static int get_swap_bios(void)
+{
+ int latch = READ_ONCE(swap_bios);
+ if (unlikely(latch <= 0))
+ latch = DEFAULT_SWAP_BIOS;
+ return latch;
+}
+
/*
* For mempools pre-allocation at the table loading time.
*/
@@ -974,6 +984,11 @@ void disable_write_zeroes(struct mapped_device *md)
limits->max_write_zeroes_sectors = 0;
}
+static bool swap_bios_limit(struct dm_target *ti, struct bio *bio)
+{
+ return unlikely((bio->bi_opf & REQ_SWAP) != 0) && unlikely(ti->limit_swap_bios);
+}
+
static void clone_endio(struct bio *bio)
{
blk_status_t error = bio->bi_status;
@@ -1025,6 +1040,11 @@ static void clone_endio(struct bio *bio)
}
}
+ if (unlikely(swap_bios_limit(tio->ti, bio))) {
+ struct mapped_device *md = io->md;
+ up(&md->swap_bios_semaphore);
+ }
+
free_tio(tio);
dec_pending(io, error);
}
@@ -1258,6 +1278,22 @@ void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors)
}
EXPORT_SYMBOL_GPL(dm_accept_partial_bio);
+static noinline void __set_swap_bios_limit(struct mapped_device *md, int latch)
+{
+ mutex_lock(&md->swap_bios_lock);
+ while (latch < md->swap_bios) {
+ cond_resched();
+ down(&md->swap_bios_semaphore);
+ md->swap_bios--;
+ }
+ while (latch > md->swap_bios) {
+ cond_resched();
+ up(&md->swap_bios_semaphore);
+ md->swap_bios++;
+ }
+ mutex_unlock(&md->swap_bios_lock);
+}
+
static blk_qc_t __map_bio(struct dm_target_io *tio)
{
int r;
@@ -1277,6 +1313,14 @@ static blk_qc_t __map_bio(struct dm_target_io *tio)
atomic_inc(&io->io_count);
sector = clone->bi_iter.bi_sector;
+ if (unlikely(swap_bios_limit(ti, clone))) {
+ struct mapped_device *md = io->md;
+ int latch = get_swap_bios();
+ if (unlikely(latch != md->swap_bios))
+ __set_swap_bios_limit(md, latch);
+ down(&md->swap_bios_semaphore);
+ }
+
r = ti->type->map(ti, clone);
switch (r) {
case DM_MAPIO_SUBMITTED:
@@ -1287,10 +1331,18 @@ static blk_qc_t __map_bio(struct dm_target_io *tio)
ret = submit_bio_noacct(clone);
break;
case DM_MAPIO_KILL:
+ if (unlikely(swap_bios_limit(ti, clone))) {
+ struct mapped_device *md = io->md;
+ up(&md->swap_bios_semaphore);
+ }
free_tio(tio);
dec_pending(io, BLK_STS_IOERR);
break;
case DM_MAPIO_REQUEUE:
+ if (unlikely(swap_bios_limit(ti, clone))) {
+ struct mapped_device *md = io->md;
+ up(&md->swap_bios_semaphore);
+ }
free_tio(tio);
dec_pending(io, BLK_STS_DM_REQUEUE);
break;
@@ -1767,6 +1819,7 @@ static void cleanup_mapped_device(struct mapped_device *md)
mutex_destroy(&md->suspend_lock);
mutex_destroy(&md->type_lock);
mutex_destroy(&md->table_devices_lock);
+ mutex_destroy(&md->swap_bios_lock);
dm_mq_cleanup_mapped_device(md);
}
@@ -1834,6 +1887,10 @@ static struct mapped_device *alloc_dev(int minor)
init_waitqueue_head(&md->eventq);
init_completion(&md->kobj_holder.completion);
+ md->swap_bios = get_swap_bios();
+ sema_init(&md->swap_bios_semaphore, md->swap_bios);
+ mutex_init(&md->swap_bios_lock);
+
md->disk->major = _major;
md->disk->first_minor = minor;
md->disk->fops = &dm_blk_dops;
@@ -3117,6 +3174,9 @@ MODULE_PARM_DESC(reserved_bio_based_ios, "Reserved IOs in bio-based mempools");
module_param(dm_numa_node, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(dm_numa_node, "NUMA node for DM device memory allocations");
+module_param(swap_bios, int, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(swap_bios, "Maximum allowed inflight swap IOs");
+
MODULE_DESCRIPTION(DM_NAME " driver");
MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");