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SubjectRe: [PATCH 2/5] Btrfs: delete the entire async bio submission framework
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On 10.07.19 г. 22:28 ч., Tejun Heo wrote:
> 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>
> Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.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 0a61dff27f57..21618b5b18a4 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 6b1ecc27913b..323cab06f2a9 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 0645ec428b4f..b130dc43b5f1 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 e532d095c6a4..819047621176 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;
>
>

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