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authorLinus Torvalds <torvalds@linux-foundation.org>2019-10-18 18:26:07 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2019-10-18 18:26:07 -0400
commitfb8527e5c13ed70057b8dfce0764ec625ec3e400 (patch)
tree8b4a8dd37a9950d33dd6a66c9cdf193a0f47273b /drivers
parent90105ae1eeef51987f40d8e2db4c9c79604fc4e4 (diff)
parent13bd677a472d534bf100bab2713efc3f9e3f5978 (diff)
Merge tag 'for-5.4/dm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper fixes from Mike Snitzer: - Fix DM snapshot deadlock that can occur due to COW throttling preventing locks from being released. - Fix DM cache's GFP_NOWAIT allocation failure error paths by switching to GFP_NOIO. - Make __hash_find() static in the DM clone target. * tag 'for-5.4/dm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: dm cache: fix bugs when a GFP_NOWAIT allocation fails dm snapshot: rework COW throttling to fix deadlock dm snapshot: introduce account_start_copy() and account_end_copy() dm clone: Make __hash_find static
Diffstat (limited to 'drivers')
-rw-r--r--drivers/md/dm-cache-target.c28
-rw-r--r--drivers/md/dm-clone-target.c4
-rw-r--r--drivers/md/dm-snap.c94
3 files changed, 81 insertions, 45 deletions
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index d249cf8ac277..8346e6d1816c 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -542,7 +542,7 @@ static void wake_migration_worker(struct cache *cache)
static struct dm_bio_prison_cell_v2 *alloc_prison_cell(struct cache *cache)
{
- return dm_bio_prison_alloc_cell_v2(cache->prison, GFP_NOWAIT);
+ return dm_bio_prison_alloc_cell_v2(cache->prison, GFP_NOIO);
}
static void free_prison_cell(struct cache *cache, struct dm_bio_prison_cell_v2 *cell)
@@ -554,9 +554,7 @@ static struct dm_cache_migration *alloc_migration(struct cache *cache)
{
struct dm_cache_migration *mg;
- mg = mempool_alloc(&cache->migration_pool, GFP_NOWAIT);
- if (!mg)
- return NULL;
+ mg = mempool_alloc(&cache->migration_pool, GFP_NOIO);
memset(mg, 0, sizeof(*mg));
@@ -664,10 +662,6 @@ static bool bio_detain_shared(struct cache *cache, dm_oblock_t oblock, struct bi
struct dm_bio_prison_cell_v2 *cell_prealloc, *cell;
cell_prealloc = alloc_prison_cell(cache); /* FIXME: allow wait if calling from worker */
- if (!cell_prealloc) {
- defer_bio(cache, bio);
- return false;
- }
build_key(oblock, end, &key);
r = dm_cell_get_v2(cache->prison, &key, lock_level(bio), bio, cell_prealloc, &cell);
@@ -1493,11 +1487,6 @@ static int mg_lock_writes(struct dm_cache_migration *mg)
struct dm_bio_prison_cell_v2 *prealloc;
prealloc = alloc_prison_cell(cache);
- if (!prealloc) {
- DMERR_LIMIT("%s: alloc_prison_cell failed", cache_device_name(cache));
- mg_complete(mg, false);
- return -ENOMEM;
- }
/*
* Prevent writes to the block, but allow reads to continue.
@@ -1535,11 +1524,6 @@ static int mg_start(struct cache *cache, struct policy_work *op, struct bio *bio
}
mg = alloc_migration(cache);
- if (!mg) {
- policy_complete_background_work(cache->policy, op, false);
- background_work_end(cache);
- return -ENOMEM;
- }
mg->op = op;
mg->overwrite_bio = bio;
@@ -1628,10 +1612,6 @@ static int invalidate_lock(struct dm_cache_migration *mg)
struct dm_bio_prison_cell_v2 *prealloc;
prealloc = alloc_prison_cell(cache);
- if (!prealloc) {
- invalidate_complete(mg, false);
- return -ENOMEM;
- }
build_key(mg->invalidate_oblock, oblock_succ(mg->invalidate_oblock), &key);
r = dm_cell_lock_v2(cache->prison, &key,
@@ -1669,10 +1649,6 @@ static int invalidate_start(struct cache *cache, dm_cblock_t cblock,
return -EPERM;
mg = alloc_migration(cache);
- if (!mg) {
- background_work_end(cache);
- return -ENOMEM;
- }
mg->overwrite_bio = bio;
mg->invalidate_cblock = cblock;
diff --git a/drivers/md/dm-clone-target.c b/drivers/md/dm-clone-target.c
index cd6f9e9fc98e..4ca8f1977222 100644
--- a/drivers/md/dm-clone-target.c
+++ b/drivers/md/dm-clone-target.c
@@ -591,8 +591,8 @@ static struct hash_table_bucket *get_hash_table_bucket(struct clone *clone,
*
* NOTE: Must be called with the bucket lock held
*/
-struct dm_clone_region_hydration *__hash_find(struct hash_table_bucket *bucket,
- unsigned long region_nr)
+static struct dm_clone_region_hydration *__hash_find(struct hash_table_bucket *bucket,
+ unsigned long region_nr)
{
struct dm_clone_region_hydration *hd;
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index f150f5c5492b..4fb1a40e68a0 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -18,7 +18,6 @@
#include <linux/vmalloc.h>
#include <linux/log2.h>
#include <linux/dm-kcopyd.h>
-#include <linux/semaphore.h>
#include "dm.h"
@@ -107,8 +106,8 @@ struct dm_snapshot {
/* The on disk metadata handler */
struct dm_exception_store *store;
- /* Maximum number of in-flight COW jobs. */
- struct semaphore cow_count;
+ unsigned in_progress;
+ struct wait_queue_head in_progress_wait;
struct dm_kcopyd_client *kcopyd_client;
@@ -162,8 +161,8 @@ struct dm_snapshot {
*/
#define DEFAULT_COW_THRESHOLD 2048
-static int cow_threshold = DEFAULT_COW_THRESHOLD;
-module_param_named(snapshot_cow_threshold, cow_threshold, int, 0644);
+static unsigned cow_threshold = DEFAULT_COW_THRESHOLD;
+module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644);
MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write");
DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,
@@ -1327,7 +1326,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
goto bad_hash_tables;
}
- sema_init(&s->cow_count, (cow_threshold > 0) ? cow_threshold : INT_MAX);
+ init_waitqueue_head(&s->in_progress_wait);
s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
if (IS_ERR(s->kcopyd_client)) {
@@ -1509,9 +1508,56 @@ static void snapshot_dtr(struct dm_target *ti)
dm_put_device(ti, s->origin);
+ WARN_ON(s->in_progress);
+
kfree(s);
}
+static void account_start_copy(struct dm_snapshot *s)
+{
+ spin_lock(&s->in_progress_wait.lock);
+ s->in_progress++;
+ spin_unlock(&s->in_progress_wait.lock);
+}
+
+static void account_end_copy(struct dm_snapshot *s)
+{
+ spin_lock(&s->in_progress_wait.lock);
+ BUG_ON(!s->in_progress);
+ s->in_progress--;
+ if (likely(s->in_progress <= cow_threshold) &&
+ unlikely(waitqueue_active(&s->in_progress_wait)))
+ wake_up_locked(&s->in_progress_wait);
+ spin_unlock(&s->in_progress_wait.lock);
+}
+
+static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins)
+{
+ if (unlikely(s->in_progress > cow_threshold)) {
+ spin_lock(&s->in_progress_wait.lock);
+ if (likely(s->in_progress > cow_threshold)) {
+ /*
+ * NOTE: this throttle doesn't account for whether
+ * the caller is servicing an IO that will trigger a COW
+ * so excess throttling may result for chunks not required
+ * to be COW'd. But if cow_threshold was reached, extra
+ * throttling is unlikely to negatively impact performance.
+ */
+ DECLARE_WAITQUEUE(wait, current);
+ __add_wait_queue(&s->in_progress_wait, &wait);
+ __set_current_state(TASK_UNINTERRUPTIBLE);
+ spin_unlock(&s->in_progress_wait.lock);
+ if (unlock_origins)
+ up_read(&_origins_lock);
+ io_schedule();
+ remove_wait_queue(&s->in_progress_wait, &wait);
+ return false;
+ }
+ spin_unlock(&s->in_progress_wait.lock);
+ }
+ return true;
+}
+
/*
* Flush a list of buffers.
*/
@@ -1527,7 +1573,7 @@ static void flush_bios(struct bio *bio)
}
}
-static int do_origin(struct dm_dev *origin, struct bio *bio);
+static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit);
/*
* Flush a list of buffers.
@@ -1540,7 +1586,7 @@ static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
while (bio) {
n = bio->bi_next;
bio->bi_next = NULL;
- r = do_origin(s->origin, bio);
+ r = do_origin(s->origin, bio, false);
if (r == DM_MAPIO_REMAPPED)
generic_make_request(bio);
bio = n;
@@ -1732,7 +1778,7 @@ static void copy_callback(int read_err, unsigned long write_err, void *context)
rb_link_node(&pe->out_of_order_node, parent, p);
rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree);
}
- up(&s->cow_count);
+ account_end_copy(s);
}
/*
@@ -1756,7 +1802,7 @@ static void start_copy(struct dm_snap_pending_exception *pe)
dest.count = src.count;
/* Hand over to kcopyd */
- down(&s->cow_count);
+ account_start_copy(s);
dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
}
@@ -1776,7 +1822,7 @@ static void start_full_bio(struct dm_snap_pending_exception *pe,
pe->full_bio = bio;
pe->full_bio_end_io = bio->bi_end_io;
- down(&s->cow_count);
+ account_start_copy(s);
callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
copy_callback, pe);
@@ -1866,7 +1912,7 @@ static void zero_callback(int read_err, unsigned long write_err, void *context)
struct bio *bio = context;
struct dm_snapshot *s = bio->bi_private;
- up(&s->cow_count);
+ account_end_copy(s);
bio->bi_status = write_err ? BLK_STS_IOERR : 0;
bio_endio(bio);
}
@@ -1880,7 +1926,7 @@ static void zero_exception(struct dm_snapshot *s, struct dm_exception *e,
dest.sector = bio->bi_iter.bi_sector;
dest.count = s->store->chunk_size;
- down(&s->cow_count);
+ account_start_copy(s);
WARN_ON_ONCE(bio->bi_private);
bio->bi_private = s;
dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio);
@@ -1916,6 +1962,11 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio)
if (!s->valid)
return DM_MAPIO_KILL;
+ if (bio_data_dir(bio) == WRITE) {
+ while (unlikely(!wait_for_in_progress(s, false)))
+ ; /* wait_for_in_progress() has slept */
+ }
+
down_read(&s->lock);
dm_exception_table_lock(&lock);
@@ -2112,7 +2163,7 @@ redirect_to_origin:
if (bio_data_dir(bio) == WRITE) {
up_write(&s->lock);
- return do_origin(s->origin, bio);
+ return do_origin(s->origin, bio, false);
}
out_unlock:
@@ -2487,15 +2538,24 @@ next_snapshot:
/*
* Called on a write from the origin driver.
*/
-static int do_origin(struct dm_dev *origin, struct bio *bio)
+static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit)
{
struct origin *o;
int r = DM_MAPIO_REMAPPED;
+again:
down_read(&_origins_lock);
o = __lookup_origin(origin->bdev);
- if (o)
+ if (o) {
+ if (limit) {
+ struct dm_snapshot *s;
+ list_for_each_entry(s, &o->snapshots, list)
+ if (unlikely(!wait_for_in_progress(s, true)))
+ goto again;
+ }
+
r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio);
+ }
up_read(&_origins_lock);
return r;
@@ -2608,7 +2668,7 @@ static int origin_map(struct dm_target *ti, struct bio *bio)
dm_accept_partial_bio(bio, available_sectors);
/* Only tell snapshots if this is a write */
- return do_origin(o->dev, bio);
+ return do_origin(o->dev, bio, true);
}
/*