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Btrfs: delete the entire async bio submission framework
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Now that we're not using btrfs_schedule_bio() anymore, delete all the
code that supported it.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Chris Mason authored and David Sterba committed Nov 18, 2019
1 parent 08635ba commit ba8a9d0
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Showing 5 changed files with 1 addition and 235 deletions.
1 change: 0 additions & 1 deletion fs/btrfs/ctree.h
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Original file line number Diff line number Diff line change
Expand Up @@ -723,7 +723,6 @@ 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;

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13 changes: 1 addition & 12 deletions fs/btrfs/disk-io.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1989,7 +1989,6 @@ 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);
Expand Down Expand Up @@ -2154,16 +2153,6 @@ 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);

Expand Down Expand Up @@ -2202,7 +2191,7 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
btrfs_alloc_workqueue(fs_info, "qgroup-rescan", flags, 1, 0);

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 &&
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1 change: 0 additions & 1 deletion fs/btrfs/super.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1669,7 +1669,6 @@ 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);
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210 changes: 0 additions & 210 deletions fs/btrfs/volumes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -397,8 +397,6 @@ static struct btrfs_device *__alloc_device(void)
INIT_LIST_HEAD(&dev->dev_alloc_list);
INIT_LIST_HEAD(&dev->post_commit_list);

spin_lock_init(&dev->io_lock);

atomic_set(&dev->reada_in_flight, 0);
atomic_set(&dev->dev_stats_ccnt, 0);
btrfs_device_data_ordered_init(dev);
Expand Down Expand Up @@ -501,212 +499,6 @@ 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;
Expand Down Expand Up @@ -6628,8 +6420,6 @@ struct btrfs_device *btrfs_alloc_device(struct btrfs_fs_info *fs_info,
else
generate_random_uuid(dev->uuid);

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

return dev;
}

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11 changes: 0 additions & 11 deletions fs/btrfs/volumes.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
};

struct btrfs_io_geometry {
/* remaining bytes before crossing a stripe */
Expand Down Expand Up @@ -68,13 +64,6 @@ struct btrfs_device {

u64 generation;

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;

/* the mode sent to blkdev_get */
Expand Down

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