[PATCH 5/8] Btrfs: delete the entire async bio submission framework

Tejun Heo
2019-06-14T00:34:15Z

From: Chris Mason <clm@fb.com>

Now that we're not using btrfs_schedule_bio() anymore, delete all the
code that supported it.

Signed-off-by: Chris Mason <clm@fb.com>
---
fs/btrfs/ctree.h | 1 -
fs/btrfs/disk-io.c | 13 +--
fs/btrfs/super.c | 1 -
fs/btrfs/volumes.c | 209 ---------------------------------------------
fs/btrfs/volumes.h | 8 --
5 files changed, 1 insertion(+), 231 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b81c331b28fa..2a5ba0f85ed3 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -989,7 +989,6 @@ struct btrfs_fs_info {
struct btrfs_workqueue *endio_meta_write_workers;
struct btrfs_workqueue *endio_write_workers;
struct btrfs_workqueue *endio_freespace_worker;
- struct btrfs_workqueue *submit_workers;
struct btrfs_workqueue *caching_workers;
struct btrfs_workqueue *readahead_workers;

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index b34240406f36..9dbe4ba3995d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2028,7 +2028,6 @@ static void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
btrfs_destroy_workqueue(fs_info->rmw_workers);
btrfs_destroy_workqueue(fs_info->endio_write_workers);
btrfs_destroy_workqueue(fs_info->endio_freespace_worker);
- btrfs_destroy_workqueue(fs_info->submit_workers);
btrfs_destroy_workqueue(fs_info->delayed_workers);
btrfs_destroy_workqueue(fs_info->caching_workers);
btrfs_destroy_workqueue(fs_info->readahead_workers);
@@ -2194,16 +2193,6 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
fs_info->caching_workers =
btrfs_alloc_workqueue(fs_info, "cache", flags, max_active, 0);

- /*
- * 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
- */
- fs_info->submit_workers =
- btrfs_alloc_workqueue(fs_info, "submit", flags,
- min_t(u64, fs_devices->num_devices,
- max_active), 64);
-
fs_info->fixup_workers =
btrfs_alloc_workqueue(fs_info, "fixup", flags, 1, 0);

@@ -2246,7 +2235,7 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
max_active), 8);

if (!(fs_info->workers && fs_info->delalloc_workers &&
- fs_info->submit_workers && fs_info->flush_workers &&
+ fs_info->flush_workers &&
fs_info->endio_workers && fs_info->endio_meta_workers &&
fs_info->endio_meta_write_workers &&
fs_info->endio_repair_workers &&
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 2c66d9ea6a3b..3fb86a7bfdf7 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1668,7 +1668,6 @@ static void btrfs_resize_thread_pool(struct btrfs_fs_info *fs_info,

btrfs_workqueue_set_max(fs_info->workers, new_pool_size);
btrfs_workqueue_set_max(fs_info->delalloc_workers, new_pool_size);
- btrfs_workqueue_set_max(fs_info->submit_workers, new_pool_size);
btrfs_workqueue_set_max(fs_info->caching_workers, new_pool_size);
btrfs_workqueue_set_max(fs_info->endio_workers, new_pool_size);
btrfs_workqueue_set_max(fs_info->endio_meta_workers, new_pool_size);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 72326cc23985..fc3a16d87869 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -509,212 +509,6 @@ btrfs_get_bdev_and_sb(const char *device_path, fmode_t flags, void *holder,
return ret;
}

-static void requeue_list(struct btrfs_pending_bios *pending_bios,
- struct bio *head, struct bio *tail)
-{
-
- struct bio *old_head;
-
- old_head = pending_bios->head;
- pending_bios->head = head;
- if (pending_bios->tail)
- tail->bi_next = old_head;
- else
- pending_bios->tail = tail;
-}
-
-/*
- * we try to collect pending bios for a device so we don't get a large
- * number of procs sending bios down to the same device. This greatly
- * improves the schedulers ability to collect and merge the bios.
- *
- * But, it also turns into a long list of bios to process and that is sure
- * to eventually make the worker thread block. The solution here is to
- * make some progress and then put this work struct back at the end of
- * the list if the block device is congested. This way, multiple devices
- * can make progress from a single worker thread.
- */
-static noinline void run_scheduled_bios(struct btrfs_device *device)
-{
- struct btrfs_fs_info *fs_info = device->fs_info;
- struct bio *pending;
- struct backing_dev_info *bdi;
- struct btrfs_pending_bios *pending_bios;
- struct bio *tail;
- struct bio *cur;
- int again = 0;
- unsigned long num_run;
- unsigned long batch_run = 0;
- unsigned long last_waited = 0;
- int force_reg = 0;
- int sync_pending = 0;
- struct blk_plug plug;
-
- /*
- * this function runs all the bios we've collected for
- * a particular device. We don't want to wander off to
- * another device without first sending all of these down.
- * So, setup a plug here and finish it off before we return
- */
- blk_start_plug(&plug);
-
- bdi = device->bdev->bd_bdi;
-
-loop:
- spin_lock(&device->io_lock);
-
-loop_lock:
- num_run = 0;
-
- /* take all the bios off the list at once and process them
- * later on (without the lock held). But, remember the
- * tail and other pointers so the bios can be properly reinserted
- * into the list if we hit congestion
- */
- if (!force_reg && device->pending_sync_bios.head) {
- pending_bios = &device->pending_sync_bios;
- force_reg = 1;
- } else {
- pending_bios = &device->pending_bios;
- force_reg = 0;
- }
-
- pending = pending_bios->head;
- tail = pending_bios->tail;
- WARN_ON(pending && !tail);
-
- /*
- * if pending was null this time around, no bios need processing
- * at all and we can stop. Otherwise it'll loop back up again
- * and do an additional check so no bios are missed.
- *
- * device->running_pending is used to synchronize with the
- * schedule_bio code.
- */
- if (device->pending_sync_bios.head == NULL &&
- device->pending_bios.head == NULL) {
- again = 0;
- device->running_pending = 0;
- } else {
- again = 1;
- device->running_pending = 1;
- }
-
- pending_bios->head = NULL;
- pending_bios->tail = NULL;
-
- spin_unlock(&device->io_lock);
-
- while (pending) {
-
- rmb();
- /* we want to work on both lists, but do more bios on the
- * sync list than the regular list
- */
- if ((num_run > 32 &&
- pending_bios != &device->pending_sync_bios &&
- device->pending_sync_bios.head) ||
- (num_run > 64 && pending_bios == &device->pending_sync_bios &&
- device->pending_bios.head)) {
- spin_lock(&device->io_lock);
- requeue_list(pending_bios, pending, tail);
- goto loop_lock;
- }
-
- cur = pending;
- pending = pending->bi_next;
- cur->bi_next = NULL;
-
- BUG_ON(atomic_read(&cur->__bi_cnt) == 0);
-
- /*
- * if we're doing the sync list, record that our
- * plug has some sync requests on it
- *
- * If we're doing the regular list and there are
- * sync requests sitting around, unplug before
- * we add more
- */
- if (pending_bios == &device->pending_sync_bios) {
- sync_pending = 1;
- } else if (sync_pending) {
- blk_finish_plug(&plug);
- blk_start_plug(&plug);
- sync_pending = 0;
- }
-
- btrfsic_submit_bio(cur);
- num_run++;
- batch_run++;
-
- cond_resched();
-
- /*
- * we made progress, there is more work to do and the bdi
- * is now congested. Back off and let other work structs
- * run instead
- */
- if (pending && bdi_write_congested(bdi) && batch_run > 8 &&
- fs_info->fs_devices->open_devices > 1) {
- struct io_context *ioc;
-
- ioc = current->io_context;
-
- /*
- * the main goal here is that we don't want to
- * block if we're going to be able to submit
- * more requests without blocking.
- *
- * This code does two great things, it pokes into
- * the elevator code from a filesystem _and_
- * it makes assumptions about how batching works.
- */
- if (ioc && ioc->nr_batch_requests > 0 &&
- time_before(jiffies, ioc->last_waited + HZ/50UL) &&
- (last_waited == 0 ||
- ioc->last_waited == last_waited)) {
- /*
- * we want to go through our batch of
- * requests and stop. So, we copy out
- * the ioc->last_waited time and test
- * against it before looping
- */
- last_waited = ioc->last_waited;
- cond_resched();
- continue;
- }
- spin_lock(&device->io_lock);
- requeue_list(pending_bios, pending, tail);
- device->running_pending = 1;
-
- spin_unlock(&device->io_lock);
- btrfs_queue_work(fs_info->submit_workers,
- &device->work);
- goto done;
- }
- }
-
- cond_resched();
- if (again)
- goto loop;
-
- spin_lock(&device->io_lock);
- if (device->pending_bios.head || device->pending_sync_bios.head)
- goto loop_lock;
- spin_unlock(&device->io_lock);
-
-done:
- blk_finish_plug(&plug);
-}
-
-static void pending_bios_fn(struct btrfs_work *work)
-{
- struct btrfs_device *device;
-
- device = container_of(work, struct btrfs_device, work);
- run_scheduled_bios(device);
-}
-
static bool device_path_matched(const char *path, struct btrfs_device *device)
{
int found;
@@ -6599,9 +6393,6 @@ struct btrfs_device *btrfs_alloc_device(struct btrfs_fs_info *fs_info,
else
generate_random_uuid(dev->uuid);

- btrfs_init_work(&dev->work, btrfs_submit_helper,
- pending_bios_fn, NULL, NULL);
-
return dev;
}

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 8c7bd79b234a..231f50dd107d 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -18,10 +18,6 @@ extern struct mutex uuid_mutex;
#define BTRFS_STRIPE_LEN SZ_64K

struct buffer_head;
-struct btrfs_pending_bios {
- struct bio *head;
- struct bio *tail;
-};

/*
* Use sequence counter to get consistent device stat data on
@@ -55,10 +51,6 @@ struct btrfs_device {

spinlock_t io_lock ____cacheline_aligned;
int running_pending;
- /* regular prio bios */
- struct btrfs_pending_bios pending_bios;
- /* sync bios */
- struct btrfs_pending_bios pending_sync_bios;

struct block_device *bdev;

--
2.17.1