A user reported a deadlock when copying a bunch of files. This is because they
were low on memory and kthreadd got hung up trying to migrate pages for an
allocation when starting the caching kthread. The page was locked by the person
starting the caching kthread. To fix this we just need to use the async thread
stuff so that the threads are already created and we don't have to worry about
deadlocks. Thanks,
Reported-by: Roman Mamedov <rm@romanrm.ru>
Signed-off-by: Josef Bacik <josef@redhat.com>
struct list_head block_groups[BTRFS_NR_RAID_TYPES];
spinlock_t lock;
struct rw_semaphore groups_sem;
struct list_head block_groups[BTRFS_NR_RAID_TYPES];
spinlock_t lock;
struct rw_semaphore groups_sem;
- atomic_t caching_threads;
wait_queue_head_t wait;
};
wait_queue_head_t wait;
};
struct list_head list;
struct mutex mutex;
wait_queue_head_t wait;
struct list_head list;
struct mutex mutex;
wait_queue_head_t wait;
+ struct btrfs_work work;
struct btrfs_block_group_cache *block_group;
u64 progress;
atomic_t count;
struct btrfs_block_group_cache *block_group;
u64 progress;
atomic_t count;
struct btrfs_workers endio_write_workers;
struct btrfs_workers endio_freespace_worker;
struct btrfs_workers submit_workers;
struct btrfs_workers endio_write_workers;
struct btrfs_workers endio_freespace_worker;
struct btrfs_workers submit_workers;
+ struct btrfs_workers caching_workers;
+
/*
* fixup workers take dirty pages that didn't properly go through
* the cow mechanism and make them safe to write. It happens
/*
* fixup workers take dirty pages that didn't properly go through
* the cow mechanism and make them safe to write. It happens
fs_info->thread_pool_size),
&fs_info->generic_worker);
fs_info->thread_pool_size),
&fs_info->generic_worker);
+ btrfs_init_workers(&fs_info->caching_workers, "cache",
+ 2, &fs_info->generic_worker);
+
/* a higher idle thresh on the submit workers makes it much more
* likely that bios will be send down in a sane order to the
* devices
/* a higher idle thresh on the submit workers makes it much more
* likely that bios will be send down in a sane order to the
* devices
btrfs_start_workers(&fs_info->endio_write_workers, 1);
btrfs_start_workers(&fs_info->endio_freespace_worker, 1);
btrfs_start_workers(&fs_info->delayed_workers, 1);
btrfs_start_workers(&fs_info->endio_write_workers, 1);
btrfs_start_workers(&fs_info->endio_freespace_worker, 1);
btrfs_start_workers(&fs_info->delayed_workers, 1);
+ btrfs_start_workers(&fs_info->caching_workers, 1);
fs_info->bdi.ra_pages *= btrfs_super_num_devices(disk_super);
fs_info->bdi.ra_pages = max(fs_info->bdi.ra_pages,
fs_info->bdi.ra_pages *= btrfs_super_num_devices(disk_super);
fs_info->bdi.ra_pages = max(fs_info->bdi.ra_pages,
btrfs_stop_workers(&fs_info->endio_freespace_worker);
btrfs_stop_workers(&fs_info->submit_workers);
btrfs_stop_workers(&fs_info->delayed_workers);
btrfs_stop_workers(&fs_info->endio_freespace_worker);
btrfs_stop_workers(&fs_info->submit_workers);
btrfs_stop_workers(&fs_info->delayed_workers);
+ btrfs_stop_workers(&fs_info->caching_workers);
fail_alloc:
kfree(fs_info->delayed_root);
fail_iput:
fail_alloc:
kfree(fs_info->delayed_root);
fail_iput:
btrfs_stop_workers(&fs_info->endio_freespace_worker);
btrfs_stop_workers(&fs_info->submit_workers);
btrfs_stop_workers(&fs_info->delayed_workers);
btrfs_stop_workers(&fs_info->endio_freespace_worker);
btrfs_stop_workers(&fs_info->submit_workers);
btrfs_stop_workers(&fs_info->delayed_workers);
+ btrfs_stop_workers(&fs_info->caching_workers);
btrfs_close_devices(fs_info->fs_devices);
btrfs_mapping_tree_free(&fs_info->mapping_tree);
btrfs_close_devices(fs_info->fs_devices);
btrfs_mapping_tree_free(&fs_info->mapping_tree);
-static int caching_kthread(void *data)
+static noinline void caching_thread(struct btrfs_work *work)
- struct btrfs_block_group_cache *block_group = data;
- struct btrfs_fs_info *fs_info = block_group->fs_info;
- struct btrfs_caching_control *caching_ctl = block_group->caching_ctl;
- struct btrfs_root *extent_root = fs_info->extent_root;
+ struct btrfs_block_group_cache *block_group;
+ struct btrfs_fs_info *fs_info;
+ struct btrfs_caching_control *caching_ctl;
+ struct btrfs_root *extent_root;
struct btrfs_path *path;
struct extent_buffer *leaf;
struct btrfs_key key;
struct btrfs_path *path;
struct extent_buffer *leaf;
struct btrfs_key key;
u32 nritems;
int ret = 0;
u32 nritems;
int ret = 0;
+ caching_ctl = container_of(work, struct btrfs_caching_control, work);
+ block_group = caching_ctl->block_group;
+ fs_info = block_group->fs_info;
+ extent_root = fs_info->extent_root;
+
path = btrfs_alloc_path();
if (!path)
path = btrfs_alloc_path();
if (!path)
last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET);
last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET);
free_excluded_extents(extent_root, block_group);
mutex_unlock(&caching_ctl->mutex);
free_excluded_extents(extent_root, block_group);
mutex_unlock(&caching_ctl->mutex);
wake_up(&caching_ctl->wait);
put_caching_control(caching_ctl);
wake_up(&caching_ctl->wait);
put_caching_control(caching_ctl);
- atomic_dec(&block_group->space_info->caching_threads);
btrfs_put_block_group(block_group);
btrfs_put_block_group(block_group);
}
static int cache_block_group(struct btrfs_block_group_cache *cache,
}
static int cache_block_group(struct btrfs_block_group_cache *cache,
{
struct btrfs_fs_info *fs_info = cache->fs_info;
struct btrfs_caching_control *caching_ctl;
{
struct btrfs_fs_info *fs_info = cache->fs_info;
struct btrfs_caching_control *caching_ctl;
- struct task_struct *tsk;
caching_ctl->progress = cache->key.objectid;
/* one for caching kthread, one for caching block group list */
atomic_set(&caching_ctl->count, 2);
caching_ctl->progress = cache->key.objectid;
/* one for caching kthread, one for caching block group list */
atomic_set(&caching_ctl->count, 2);
+ caching_ctl->work.func = caching_thread;
spin_lock(&cache->lock);
if (cache->cached != BTRFS_CACHE_NO) {
spin_lock(&cache->lock);
if (cache->cached != BTRFS_CACHE_NO) {
list_add_tail(&caching_ctl->list, &fs_info->caching_block_groups);
up_write(&fs_info->extent_commit_sem);
list_add_tail(&caching_ctl->list, &fs_info->caching_block_groups);
up_write(&fs_info->extent_commit_sem);
- atomic_inc(&cache->space_info->caching_threads);
btrfs_get_block_group(cache);
btrfs_get_block_group(cache);
- tsk = kthread_run(caching_kthread, cache, "btrfs-cache-%llu\n",
- cache->key.objectid);
- if (IS_ERR(tsk)) {
- ret = PTR_ERR(tsk);
- printk(KERN_ERR "error running thread %d\n", ret);
- BUG();
- }
+ btrfs_queue_worker(&fs_info->caching_workers, &caching_ctl->work);
init_waitqueue_head(&found->wait);
*space_info = found;
list_add_rcu(&found->list, &info->space_info);
init_waitqueue_head(&found->wait);
*space_info = found;
list_add_rcu(&found->list, &info->space_info);
- atomic_set(&found->caching_threads, 0);
- * We only want to start kthread caching if we are at
- * the point where we will wait for caching to make
- * progress, or if our ideal search is over and we've
- * found somebody to start caching.
+ * The caching workers are limited to 2 threads, so we
+ * can queue as much work as we care to.
- if (loop > LOOP_CACHING_NOWAIT ||
- (loop > LOOP_FIND_IDEAL &&
- atomic_read(&space_info->caching_threads) < 2)) {
+ if (loop > LOOP_FIND_IDEAL) {
ret = cache_block_group(block_group, trans,
orig_root, 0);
BUG_ON(ret);
ret = cache_block_group(block_group, trans,
orig_root, 0);
BUG_ON(ret);
if (loop == LOOP_FIND_IDEAL && found_uncached_bg) {
found_uncached_bg = false;
loop++;
if (loop == LOOP_FIND_IDEAL && found_uncached_bg) {
found_uncached_bg = false;
loop++;
- if (!ideal_cache_percent &&
- atomic_read(&space_info->caching_threads))
+ if (!ideal_cache_percent)