dm: support bio polling
Support bio polling (REQ_POLLED) in the following approach: 1) only support io polling on normal READ/WRITE, and other abnormal IOs still fallback to IRQ mode, so the target io (and DM's clone bio) is exactly inside the dm io. 2) hold one refcnt on io->io_count after submitting this dm bio with REQ_POLLED 3) support dm native bio splitting, any dm io instance associated with current bio will be added into one list which head is bio->bi_private which will be recovered before ending this bio 4) implement .poll_bio() callback, call bio_poll() on the single target bio inside the dm io which is retrieved via bio->bi_bio_drv_data; call dm_io_dec_pending() after the target io is done in .poll_bio() 5) enable QUEUE_FLAG_POLL if all underlying queues enable QUEUE_FLAG_POLL, which is based on Jeffle's previous patch. These changes are good for a 30-35% IOPS improvement for polled IO. For detailed test results please see (Jens, thanks for testing!): https://listman.redhat.com/archives/dm-devel/2022-March/049868.html or https://marc.info/?l=linux-block&m=164684246214700&w=2 Tested-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Ming Lei
Mike Snitzer
Родитель
69fe0f2989
Коммит
b99fdcdc36
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@ -235,6 +235,8 @@ struct dm_io {
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bool start_io_acct:1;
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int was_accounted;
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unsigned long start_time;
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void *data;
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struct hlist_node node;
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spinlock_t endio_lock;
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struct dm_stats_aux stats_aux;
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/* last member of dm_target_io is 'struct bio' */
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@ -1481,6 +1481,14 @@ struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
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return &t->targets[(KEYS_PER_NODE * n) + k];
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}
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static int device_not_poll_capable(struct dm_target *ti, struct dm_dev *dev,
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sector_t start, sector_t len, void *data)
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{
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struct request_queue *q = bdev_get_queue(dev->bdev);
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return !test_bit(QUEUE_FLAG_POLL, &q->queue_flags);
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}
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/*
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* type->iterate_devices() should be called when the sanity check needs to
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* iterate and check all underlying data devices. iterate_devices() will
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@ -1531,6 +1539,11 @@ static int count_device(struct dm_target *ti, struct dm_dev *dev,
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return 0;
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}
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static int dm_table_supports_poll(struct dm_table *t)
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{
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return !dm_table_any_dev_attr(t, device_not_poll_capable, NULL);
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}
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/*
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* Check whether a table has no data devices attached using each
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* target's iterate_devices method.
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@ -2067,6 +2080,20 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
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dm_update_crypto_profile(q, t);
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disk_update_readahead(t->md->disk);
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/*
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* Check for request-based device is left to
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* dm_mq_init_request_queue()->blk_mq_init_allocated_queue().
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*
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* For bio-based device, only set QUEUE_FLAG_POLL when all
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* underlying devices supporting polling.
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*/
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if (__table_type_bio_based(t->type)) {
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if (dm_table_supports_poll(t))
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blk_queue_flag_set(QUEUE_FLAG_POLL, q);
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else
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blk_queue_flag_clear(QUEUE_FLAG_POLL, q);
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}
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return 0;
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}
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143
drivers/md/dm.c
143
drivers/md/dm.c
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@ -40,6 +40,13 @@
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#define DM_COOKIE_ENV_VAR_NAME "DM_COOKIE"
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#define DM_COOKIE_LENGTH 24
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/*
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* For REQ_POLLED fs bio, this flag is set if we link mapped underlying
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* dm_io into one list, and reuse bio->bi_private as the list head. Before
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* ending this fs bio, we will recover its ->bi_private.
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*/
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#define REQ_DM_POLL_LIST REQ_DRV
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static const char *_name = DM_NAME;
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static unsigned int major = 0;
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@ -73,6 +80,7 @@ struct clone_info {
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struct dm_io *io;
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sector_t sector;
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unsigned sector_count;
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bool submit_as_polled;
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};
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#define DM_TARGET_IO_BIO_OFFSET (offsetof(struct dm_target_io, clone))
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@ -599,6 +607,9 @@ static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti,
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if (!clone)
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return NULL;
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/* REQ_DM_POLL_LIST shouldn't be inherited */
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clone->bi_opf &= ~REQ_DM_POLL_LIST;
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tio = clone_to_tio(clone);
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tio->inside_dm_io = false;
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}
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@ -888,8 +899,15 @@ void dm_io_dec_pending(struct dm_io *io, blk_status_t error)
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if (unlikely(wq_has_sleeper(&md->wait)))
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wake_up(&md->wait);
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if (io_error == BLK_STS_DM_REQUEUE)
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if (io_error == BLK_STS_DM_REQUEUE) {
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/*
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* Upper layer won't help us poll split bio, io->orig_bio
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* may only reflect a subset of the pre-split original,
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* so clear REQ_POLLED in case of requeue
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*/
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bio->bi_opf &= ~REQ_POLLED;
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return;
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}
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if (bio_is_flush_with_data(bio)) {
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/*
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@ -1440,6 +1458,47 @@ static bool __process_abnormal_io(struct clone_info *ci, struct dm_target *ti,
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return true;
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}
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/*
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* Reuse ->bi_private as hlist head for storing all dm_io instances
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* associated with this bio, and this bio's bi_private needs to be
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* stored in dm_io->data before the reuse.
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*
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* bio->bi_private is owned by fs or upper layer, so block layer won't
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* touch it after splitting. Meantime it won't be changed by anyone after
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* bio is submitted. So this reuse is safe.
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*/
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static inline struct hlist_head *dm_get_bio_hlist_head(struct bio *bio)
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{
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return (struct hlist_head *)&bio->bi_private;
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}
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static void dm_queue_poll_io(struct bio *bio, struct dm_io *io)
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{
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struct hlist_head *head = dm_get_bio_hlist_head(bio);
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if (!(bio->bi_opf & REQ_DM_POLL_LIST)) {
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bio->bi_opf |= REQ_DM_POLL_LIST;
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/*
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* Save .bi_private into dm_io, so that we can reuse
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* .bi_private as hlist head for storing dm_io list
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*/
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io->data = bio->bi_private;
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INIT_HLIST_HEAD(head);
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/* tell block layer to poll for completion */
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bio->bi_cookie = ~BLK_QC_T_NONE;
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} else {
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/*
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* bio recursed due to split, reuse original poll list,
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* and save bio->bi_private too.
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*/
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io->data = hlist_entry(head->first, struct dm_io, node)->data;
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}
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hlist_add_head(&io->node, head);
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}
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/*
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* Select the correct strategy for processing a non-flush bio.
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*/
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@ -1457,6 +1516,12 @@ static int __split_and_process_bio(struct clone_info *ci)
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if (__process_abnormal_io(ci, ti, &r))
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return r;
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/*
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* Only support bio polling for normal IO, and the target io is
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* exactly inside the dm_io instance (verified in dm_poll_dm_io)
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*/
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ci->submit_as_polled = ci->bio->bi_opf & REQ_POLLED;
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len = min_t(sector_t, max_io_len(ti, ci->sector), ci->sector_count);
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clone = alloc_tio(ci, ti, 0, &len, GFP_NOIO);
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__map_bio(clone);
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@ -1473,6 +1538,7 @@ static void init_clone_info(struct clone_info *ci, struct mapped_device *md,
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ci->map = map;
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ci->io = alloc_io(md, bio);
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ci->bio = bio;
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ci->submit_as_polled = false;
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ci->sector = bio->bi_iter.bi_sector;
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ci->sector_count = bio_sectors(bio);
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@ -1522,8 +1588,17 @@ out:
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if (ci.io->start_io_acct)
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dm_start_io_acct(ci.io, NULL);
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/* drop the extra reference count */
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dm_io_dec_pending(ci.io, errno_to_blk_status(error));
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/*
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* Drop the extra reference count for non-POLLED bio, and hold one
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* reference for POLLED bio, which will be released in dm_poll_bio
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*
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* Add every dm_io instance into the hlist_head which is stored in
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* bio->bi_private, so that dm_poll_bio can poll them all.
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*/
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if (error || !ci.submit_as_polled)
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dm_io_dec_pending(ci.io, errno_to_blk_status(error));
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else
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dm_queue_poll_io(bio, ci.io);
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}
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static void dm_submit_bio(struct bio *bio)
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@ -1558,6 +1633,67 @@ out:
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dm_put_live_table(md, srcu_idx);
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}
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static bool dm_poll_dm_io(struct dm_io *io, struct io_comp_batch *iob,
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unsigned int flags)
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{
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WARN_ON_ONCE(!io->tio.inside_dm_io);
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/* don't poll if the mapped io is done */
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if (atomic_read(&io->io_count) > 1)
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bio_poll(&io->tio.clone, iob, flags);
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/* bio_poll holds the last reference */
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return atomic_read(&io->io_count) == 1;
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}
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static int dm_poll_bio(struct bio *bio, struct io_comp_batch *iob,
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unsigned int flags)
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{
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struct hlist_head *head = dm_get_bio_hlist_head(bio);
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struct hlist_head tmp = HLIST_HEAD_INIT;
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struct hlist_node *next;
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struct dm_io *io;
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/* Only poll normal bio which was marked as REQ_DM_POLL_LIST */
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if (!(bio->bi_opf & REQ_DM_POLL_LIST))
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return 0;
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WARN_ON_ONCE(hlist_empty(head));
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hlist_move_list(head, &tmp);
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/*
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* Restore .bi_private before possibly completing dm_io.
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*
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* bio_poll() is only possible once @bio has been completely
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* submitted via submit_bio_noacct()'s depth-first submission.
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* So there is no dm_queue_poll_io() race associated with
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* clearing REQ_DM_POLL_LIST here.
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*/
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bio->bi_opf &= ~REQ_DM_POLL_LIST;
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bio->bi_private = hlist_entry(tmp.first, struct dm_io, node)->data;
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hlist_for_each_entry_safe(io, next, &tmp, node) {
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if (dm_poll_dm_io(io, iob, flags)) {
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hlist_del_init(&io->node);
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/*
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* clone_endio() has already occurred, so passing
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* error as 0 here doesn't override io->status
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*/
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dm_io_dec_pending(io, 0);
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}
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}
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/* Not done? */
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if (!hlist_empty(&tmp)) {
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bio->bi_opf |= REQ_DM_POLL_LIST;
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/* Reset bio->bi_private to dm_io list head */
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hlist_move_list(&tmp, head);
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return 0;
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}
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return 1;
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}
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/*-----------------------------------------------------------------
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* An IDR is used to keep track of allocated minor numbers.
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*---------------------------------------------------------------*/
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@ -2983,6 +3119,7 @@ static const struct pr_ops dm_pr_ops = {
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static const struct block_device_operations dm_blk_dops = {
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.submit_bio = dm_submit_bio,
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.poll_bio = dm_poll_bio,
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.open = dm_blk_open,
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.release = dm_blk_close,
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.ioctl = dm_blk_ioctl,
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