6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
commit 2a695062a5a42aead8c539a344168d4806b3fda2 upstream.
dm-bufio has a no-sleep mode. When activated (with the
DM_BUFIO_CLIENT_NO_SLEEP flag), the bufio client is read-only and we
could call dm_bufio_get from tasklets. This is used by dm-verity.
Unfortunately, commit 450e8dee51aa ("dm bufio: improve concurrent IO
performance") broke this and the kernel would warn that cache_get()
was calling down_read() from no-sleeping context. The bug can be
reproduced by using "veritysetup open" with the "--use-tasklets"
flag.
This commit fixes dm-bufio, so that the tasklet mode works again, by
expanding use of the 'no_sleep_enabled' static_key to conditionally
use either a rw_semaphore or rwlock_t (which are colocated in the
buffer_tree structure using a union).
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v6.4
Fixes: 450e8dee51aa ("dm bufio: improve concurrent IO performance")
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-bufio.c | 87 ++++++++++++++++++++++++++++++-------------
1 file changed, 62 insertions(+), 25 deletions(-)
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 62eb27639c9b..f03d7dba270c 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -254,7 +254,7 @@ enum evict_result {
typedef enum evict_result (*le_predicate)(struct lru_entry *le, void *context);
-static struct lru_entry *lru_evict(struct lru *lru, le_predicate pred, void *context)
+static struct lru_entry *lru_evict(struct lru *lru, le_predicate pred, void *context, bool no_sleep)
{
unsigned long tested = 0;
struct list_head *h = lru->cursor;
@@ -295,7 +295,8 @@ static struct lru_entry *lru_evict(struct lru *lru, le_predicate pred, void *con
h = h->next;
- cond_resched();
+ if (!no_sleep)
+ cond_resched();
}
return NULL;
@@ -382,7 +383,10 @@ struct dm_buffer {
*/
struct buffer_tree {
- struct rw_semaphore lock;
+ union {
+ struct rw_semaphore lock;
+ rwlock_t spinlock;
+ } u;
struct rb_root root;
} ____cacheline_aligned_in_smp;
@@ -393,9 +397,12 @@ struct dm_buffer_cache {
* on the locks.
*/
unsigned int num_locks;
+ bool no_sleep;
struct buffer_tree trees[];
};
+static DEFINE_STATIC_KEY_FALSE(no_sleep_enabled);
+
static inline unsigned int cache_index(sector_t block, unsigned int num_locks)
{
return dm_hash_locks_index(block, num_locks);
@@ -403,22 +410,34 @@ static inline unsigned int cache_index(sector_t block, unsigned int num_locks)
static inline void cache_read_lock(struct dm_buffer_cache *bc, sector_t block)
{
- down_read(&bc->trees[cache_index(block, bc->num_locks)].lock);
+ if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
+ read_lock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
+ else
+ down_read(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
}
static inline void cache_read_unlock(struct dm_buffer_cache *bc, sector_t block)
{
- up_read(&bc->trees[cache_index(block, bc->num_locks)].lock);
+ if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
+ read_unlock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
+ else
+ up_read(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
}
static inline void cache_write_lock(struct dm_buffer_cache *bc, sector_t block)
{
- down_write(&bc->trees[cache_index(block, bc->num_locks)].lock);
+ if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
+ write_lock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
+ else
+ down_write(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
}
static inline void cache_write_unlock(struct dm_buffer_cache *bc, sector_t block)
{
- up_write(&bc->trees[cache_index(block, bc->num_locks)].lock);
+ if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
+ write_unlock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
+ else
+ up_write(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
}
/*
@@ -442,18 +461,32 @@ static void lh_init(struct lock_history *lh, struct dm_buffer_cache *cache, bool
static void __lh_lock(struct lock_history *lh, unsigned int index)
{
- if (lh->write)
- down_write(&lh->cache->trees[index].lock);
- else
- down_read(&lh->cache->trees[index].lock);
+ if (lh->write) {
+ if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
+ write_lock_bh(&lh->cache->trees[index].u.spinlock);
+ else
+ down_write(&lh->cache->trees[index].u.lock);
+ } else {
+ if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
+ read_lock_bh(&lh->cache->trees[index].u.spinlock);
+ else
+ down_read(&lh->cache->trees[index].u.lock);
+ }
}
static void __lh_unlock(struct lock_history *lh, unsigned int index)
{
- if (lh->write)
- up_write(&lh->cache->trees[index].lock);
- else
- up_read(&lh->cache->trees[index].lock);
+ if (lh->write) {
+ if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
+ write_unlock_bh(&lh->cache->trees[index].u.spinlock);
+ else
+ up_write(&lh->cache->trees[index].u.lock);
+ } else {
+ if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
+ read_unlock_bh(&lh->cache->trees[index].u.spinlock);
+ else
+ up_read(&lh->cache->trees[index].u.lock);
+ }
}
/*
@@ -502,14 +535,18 @@ static struct dm_buffer *list_to_buffer(struct list_head *l)
return le_to_buffer(le);
}
-static void cache_init(struct dm_buffer_cache *bc, unsigned int num_locks)
+static void cache_init(struct dm_buffer_cache *bc, unsigned int num_locks, bool no_sleep)
{
unsigned int i;
bc->num_locks = num_locks;
+ bc->no_sleep = no_sleep;
for (i = 0; i < bc->num_locks; i++) {
- init_rwsem(&bc->trees[i].lock);
+ if (no_sleep)
+ rwlock_init(&bc->trees[i].u.spinlock);
+ else
+ init_rwsem(&bc->trees[i].u.lock);
bc->trees[i].root = RB_ROOT;
}
@@ -648,7 +685,7 @@ static struct dm_buffer *__cache_evict(struct dm_buffer_cache *bc, int list_mode
struct lru_entry *le;
struct dm_buffer *b;
- le = lru_evict(&bc->lru[list_mode], __evict_pred, &w);
+ le = lru_evict(&bc->lru[list_mode], __evict_pred, &w, bc->no_sleep);
if (!le)
return NULL;
@@ -702,7 +739,7 @@ static void __cache_mark_many(struct dm_buffer_cache *bc, int old_mode, int new_
struct evict_wrapper w = {.lh = lh, .pred = pred, .context = context};
while (true) {
- le = lru_evict(&bc->lru[old_mode], __evict_pred, &w);
+ le = lru_evict(&bc->lru[old_mode], __evict_pred, &w, bc->no_sleep);
if (!le)
break;
@@ -915,10 +952,11 @@ static void cache_remove_range(struct dm_buffer_cache *bc,
{
unsigned int i;
+ BUG_ON(bc->no_sleep);
for (i = 0; i < bc->num_locks; i++) {
- down_write(&bc->trees[i].lock);
+ down_write(&bc->trees[i].u.lock);
__remove_range(bc, &bc->trees[i].root, begin, end, pred, release);
- up_write(&bc->trees[i].lock);
+ up_write(&bc->trees[i].u.lock);
}
}
@@ -979,8 +1017,6 @@ struct dm_bufio_client {
struct dm_buffer_cache cache; /* must be last member */
};
-static DEFINE_STATIC_KEY_FALSE(no_sleep_enabled);
-
/*----------------------------------------------------------------*/
#define dm_bufio_in_request() (!!current->bio_list)
@@ -1871,7 +1907,8 @@ static void *new_read(struct dm_bufio_client *c, sector_t block,
if (need_submit)
submit_io(b, REQ_OP_READ, read_endio);
- wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
+ if (nf != NF_GET) /* we already tested this condition above */
+ wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
if (b->read_error) {
int error = blk_status_to_errno(b->read_error);
@@ -2421,7 +2458,7 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
r = -ENOMEM;
goto bad_client;
}
- cache_init(&c->cache, num_locks);
+ cache_init(&c->cache, num_locks, (flags & DM_BUFIO_CLIENT_NO_SLEEP) != 0);
c->bdev = bdev;
c->block_size = block_size;
--
2.43.0
