On 4/2/24 14:38, Damien Le Moal wrote:
Zone write plugging implements a per-zone "plug" for write operations
to control the submission and execution order of write operations to
sequential write required zones of a zoned block device. Per-zone
plugging guarantees that at any time there is at most only one write
request per zone being executed. This mechanism is intended to replace
zone write locking which implements a similar per-zone write throttling
at the scheduler level, but is implemented only by mq-deadline.
Unlike zone write locking which operates on requests, zone write
plugging operates on BIOs. A zone write plug is simply a BIO list that
is atomically manipulated using a spinlock and a kblockd submission
work. A write BIO to a zone is "plugged" to delay its execution if a
write BIO for the same zone was already issued, that is, if a write
request for the same zone is being executed. The next plugged BIO is
unplugged and issued once the write request completes.
This mechanism allows to:
- Untangle zone write ordering from block IO schedulers. This allows
removing the restriction on using mq-deadline for writing to zoned
block devices. Any block IO scheduler, including "none" can be used.
- Zone write plugging operates on BIOs instead of requests. Plugged
BIOs waiting for execution thus do not hold scheduling tags and thus
are not preventing other BIOs from executing (reads or writes to
other zones). Depending on the workload, this can significantly
improve the device use (higher queue depth operation) and
performance.
- Both blk-mq (request based) zoned devices and BIO-based zoned devices
(e.g. device mapper) can use zone write plugging. It is mandatory
for the former but optional for the latter. BIO-based drivers can
use zone write plugging to implement write ordering guarantees, or
the drivers can implement their own if needed.
- The code is less invasive in the block layer and is mostly limited to
blk-zoned.c with some small changes in blk-mq.c, blk-merge.c and
bio.c.
Zone write plugging is implemented using struct blk_zone_wplug. This
structure includes a spinlock, a BIO list and a work structure to
handle the submission of plugged BIOs. Zone write plugs structures are
managed using a per-disk hash table.
Plugging of zone write BIOs is done using the function
blk_zone_write_plug_bio() which returns false if a BIO execution does
not need to be delayed and true otherwise. This function is called
from blk_mq_submit_bio() after a BIO is split to avoid large BIOs
spanning multiple zones which would cause mishandling of zone write
plugs. This ichange enables by default zone write plugging for any mq
request-based block device. BIO-based device drivers can also use zone
write plugging by expliclty calling blk_zone_write_plug_bio() in their
->submit_bio method. For such devices, the driver must ensure that a
BIO passed to blk_zone_write_plug_bio() is already split and not
straddling zone boundaries.
Only write and write zeroes BIOs are plugged. Zone write plugging does
not introduce any significant overhead for other operations. A BIO that
is being handled through zone write plugging is flagged using the new
BIO flag BIO_ZONE_WRITE_PLUGGING. A request handling a BIO flagged with
this new flag is flagged with the new RQF_ZONE_WRITE_PLUGGING flag.
The completion of BIOs and requests flagged trigger respectively calls
to the functions blk_zone_write_plug_bio_endio() and
blk_zone_write_plug_complete_request(). The latter function is used to
trigger submission of the next plugged BIO using the zone plug work.
blk_zone_write_plug_bio_endio() does the same for BIO-based devices.
This ensures that at any time, at most one request (blk-mq devices) or
one BIO (BIO-based devices) is being executed for any zone. The
handling of zone write plugs using a per-zone plug spinlock maximizes
parallelism and device usage by allowing multiple zones to be writen
simultaneously without lock contention.
Zone write plugging ignores flush BIOs without data. Hovever, any flush
BIO that has data is always plugged so that the write part of the flush
sequence is serialized with other regular writes.
Given that any BIO handled through zone write plugging will be the only
BIO in flight for the target zone when it is executed, the unplugging
and submission of a BIO will have no chance of successfully merging with
plugged requests or requests in the scheduler. To overcome this
potential performance degradation, blk_mq_submit_bio() calls the
function blk_zone_write_plug_attempt_merge() to try to merge other
plugged BIOs with the one just unplugged and submitted. Successful
merging is signaled using blk_zone_write_plug_bio_merged(), called from
bio_attempt_back_merge(). Furthermore, to avoid recalculating the number
of segments of plugged BIOs to attempt merging, the number of segments
of a plugged BIO is saved using the new struct bio field
__bi_nr_segments. To avoid growing the size of struct bio, this field is
added as a union with the bio_cookie field. This is safe to do as
polling is always disabled for plugged BIOs.
When BIOs are plugged in a zone write plug, the device request queue
usage counter is always incremented. This reference is kept and reused
for blk-mq devices when the plugged BIO is unplugged and submitted
again using submit_bio_noacct_nocheck(). For this case, the unplugged
BIO is already flagged with BIO_ZONE_WRITE_PLUGGING and
blk_mq_submit_bio() proceeds directly to allocating a new request for
the BIO, re-using the usage reference count taken when the BIO was
plugged. This extra reference count is dropped in
blk_zone_write_plug_attempt_merge() for any plugged BIO that is
successfully merged. Given that BIO-based devices will not take this
path, the extra reference is dropped after a plugged BIO is unplugged
and submitted.
Zone write plugs are dynamically allocated and managed using a hash
table (an array of struct hlist_head) with RCU protection.
A zone write plug is allocated when a write BIO is received for the
zone and not freed until the zone is fully written, reset or finished.
To detect when a zone write plug can be freed, the write state of each
zone is tracked using a write pointer offset which corresponds to the
offset of a zone write pointer relative to the zone start. Write
operations always increment this write pointer offset. Zone reset
operations set it to 0 and zone finish operations set it to the zone
size.
If a write error happens, the wp_offset value of a zone write plug may
become incorrect and out of sync with the device managed write pointer.
This is handled using the zone write plug flag BLK_ZONE_WPLUG_ERROR.
The function blk_zone_wplug_handle_error() is called from the new disk
zone write plug work when this flag is set. This function executes a
report zone to update the zone write pointer offset to the current
value as indicated by the device. The disk zone write plug work is
scheduled whenever a BIO flagged with BIO_ZONE_WRITE_PLUGGING completes
with an error or when bio_zone_wplug_prepare_bio() detects an unaligned
write. Once scheduled, the disk zone write plugs work keeps running
until all zone errors are handled.
To match the new data structures used for zoned disks, the function
disk_free_zone_bitmaps() is renamed to the more generic
disk_free_zone_resources(). The function disk_init_zone_resources() is
also introduced to initialize zone write plugs resources when a gendisk
is allocated.
In order to guarantee that the user can simultaneously write up to a
number of zones equal to a device max active zone limit or max open zone
limit, zone write plugs are allocated using a mempool sized to the
maximum of these 2 device limits. For a device that does not have
active and open zone limits, 128 is used as the default mempool size.
If a change to the device active and open zone limits is detected, the
disk mempool is resized when blk_revalidate_disk_zones() is executed.
This commit contains contributions from Christoph Hellwig <hch@xxxxxx>.
Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
---
block/bio.c | 7 +
block/blk-merge.c | 11 +
block/blk-mq.c | 38 +-
block/blk-zoned.c | 1107 ++++++++++++++++++++++++++++++++++++-
block/blk.h | 36 +-
block/genhd.c | 3 +-
include/linux/blk-mq.h | 2 +
include/linux/blk_types.h | 8 +-
include/linux/blkdev.h | 13 +
9 files changed, 1214 insertions(+), 11 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index d24420ed1c4c..4ece8cef1fbe 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1576,6 +1576,13 @@ void bio_endio(struct bio *bio)
if (!bio_integrity_endio(bio))
return;
+ /*
+ * For BIOs handled through a zone write plug, signal the completion
+ * of the BIO so that the next plugged BIO can be submitted.
+ */
+ if (bio_zone_write_plugging(bio))
+ blk_zone_write_plug_bio_endio(bio);
+
Can't we move this check into blk_zone_write_plug_bio_endio()?
We'd need to check it anyway ...
rq_qos_done_bio(bio);
if (bio->bi_bdev && bio_flagged(bio, BIO_TRACE_COMPLETION)) {
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 3363b1321908..7a9f8187ea62 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -377,6 +377,7 @@ struct bio *__bio_split_to_limits(struct bio *bio,
blkcg_bio_issue_init(split);
bio_chain(split, bio);
trace_block_split(split, bio->bi_iter.bi_sector);
+ WARN_ON_ONCE(bio_zone_write_plugging(bio));
submit_bio_noacct(bio);
return split;
}
@@ -988,6 +989,9 @@ enum bio_merge_status bio_attempt_back_merge(struct request *req,
blk_update_mixed_merge(req, bio, false);
+ if (req->rq_flags & RQF_ZONE_WRITE_PLUGGING)
+ blk_zone_write_plug_bio_merged(bio);
+
Similar here
req->biotail->bi_next = bio;
req->biotail = bio;
req->__data_len += bio->bi_iter.bi_size;
@@ -1003,6 +1007,13 @@ static enum bio_merge_status bio_attempt_front_merge(struct request *req,
{
const blk_opf_t ff = bio_failfast(bio);
+ /*
+ * A front merge for zone writes can happen only if the user submitted
+ * writes out of order. Do not attempt this to let the write fail.
+ */
+ if (req->rq_flags & RQF_ZONE_WRITE_PLUGGING)
+ return BIO_MERGE_FAILED;
+
if (!ll_front_merge_fn(req, bio, nr_segs))
return BIO_MERGE_FAILED;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 88b541e8873f..73f2ca7c738d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -828,6 +828,9 @@ static void blk_complete_request(struct request *req)
bio = next;
} while (bio);
+ if (req->rq_flags & RQF_ZONE_WRITE_PLUGGING)
+ blk_zone_write_plug_complete_request(req);
+
And here.
/*
* Reset counters so that the request stacking driver
* can find how many bytes remain in the request
@@ -939,6 +942,9 @@ bool blk_update_request(struct request *req, blk_status_t error,
* completely done
*/
if (!req->bio) {
+ if (req->rq_flags & RQF_ZONE_WRITE_PLUGGING)
+ blk_zone_write_plug_complete_request(req);
+
And here.
/*
* Reset counters so that the request stacking driver
* can find how many bytes remain in the request
@@ -2963,15 +2969,30 @@ void blk_mq_submit_bio(struct bio *bio)
struct request *rq;
blk_status_t ret;
+ /*
+ * If the plug has a cached request for this queue, try use it.
+ */
+ rq = blk_mq_peek_cached_request(plug, q, bio->bi_opf);
+
+ /*
+ * A BIO that was released from a zone write plug has already been
+ * through the preparation in this function, already holds a reference
+ * on the queue usage counter, and is the only write BIO in-flight for
+ * the target zone. Go straight to preparing a request for it.
+ */
+ if (bio_zone_write_plugging(bio)) {
+ nr_segs = bio->__bi_nr_segments;
+ if (rq)
+ blk_queue_exit(q);
+ goto new_request;
+ }
+
bio = blk_queue_bounce(bio, q);
/*
- * If the plug has a cached request for this queue, try use it.
- *
* The cached request already holds a q_usage_counter reference and we
* don't have to acquire a new one if we use it.
*/
- rq = blk_mq_peek_cached_request(plug, q, bio->bi_opf);
if (!rq) {
if (unlikely(bio_queue_enter(bio)))
return;
@@ -2988,6 +3009,10 @@ void blk_mq_submit_bio(struct bio *bio)
if (blk_mq_attempt_bio_merge(q, bio, nr_segs))
goto queue_exit;
+ if (blk_queue_is_zoned(q) && blk_zone_write_plug_bio(bio, nr_segs))
+ goto queue_exit;
+
+new_request:
if (!rq) {
rq = blk_mq_get_new_requests(q, plug, bio, nr_segs);
if (unlikely(!rq))
@@ -3004,8 +3029,12 @@ void blk_mq_submit_bio(struct bio *bio)
ret = blk_crypto_rq_get_keyslot(rq);
if (ret != BLK_STS_OK) {
+ bool zwplugging = bio_zone_write_plugging(bio);
+
bio->bi_status = ret;
bio_endio(bio);
+ if (zwplugging)
+ blk_zone_write_plug_complete_request(rq);
blk_mq_free_request(rq);
return;
}
@@ -3013,6 +3042,9 @@ void blk_mq_submit_bio(struct bio *bio)
if (op_is_flush(bio->bi_opf) && blk_insert_flush(rq))
return;
+ if (bio_zone_write_plugging(bio))
+ blk_zone_write_plug_attempt_merge(rq);
+
And here.
if (plug) {
blk_add_rq_to_plug(plug, rq);
return;
diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 23d9bb21c459..c6130f17f359 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -7,6 +7,7 @@
*
* Copyright (c) 2016, Damien Le Moal
* Copyright (c) 2016, Western Digital
+ * Copyright (c) 2024, Western Digital Corporation or its affiliates.
*/
#include <linux/kernel.h>
@@ -16,8 +17,11 @@
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <linux/sched/mm.h>
+#include <linux/spinlock.h>
+#include <linux/atomic.h>
#include "blk.h"
+#include "blk-mq-sched.h"
#define ZONE_COND_NAME(name) [BLK_ZONE_COND_##name] = #name
static const char *const zone_cond_name[] = {
@@ -32,6 +36,64 @@ static const char *const zone_cond_name[] = {
};
#undef ZONE_COND_NAME
+/*
+ * Per-zone write plug.
+ * @node: hlist_node structure for managing the plug using a hash table.
+ * @link: To list the plug in the zone write plug error list of the disk.
+ * @ref: Zone write plug reference counter. A zone write plug reference is
+ * always at least 1 when the plug is hashed in the disk plug hash table.
+ * The reference is incremented whenever a new BIO needing plugging is
+ * submitted and when a function needs to manipulate a plug. The
+ * reference count is decremented whenever a plugged BIO completes and
+ * when a function that referenced the plug returns. The initial
+ * reference is dropped whenever the zone of the zone write plug is reset,
+ * finished and when the zone becomes full (last write BIO to the zone
+ * completes).
+ * @lock: Spinlock to atomically manipulate the plug.
+ * @flags: Flags indicating the plug state.
+ * @zone_no: The number of the zone the plug is managing.
+ * @wp_offset: The zone write pointer location relative to the start of the zone
+ * as a number of 512B sectors.
+ * @bio_list: The list of BIOs that are currently plugged.
+ * @bio_work: Work struct to handle issuing of plugged BIOs
+ * @rcu_head: RCU head to free zone write plugs with an RCU grace period.
+ * @disk: The gendisk the plug belongs to.
+ */
+struct blk_zone_wplug {
+ struct hlist_node node;
+ struct list_head link;
+ atomic_t ref;
+ spinlock_t lock;
+ unsigned int flags;
+ unsigned int zone_no;
+ unsigned int wp_offset;
+ struct bio_list bio_list;
+ struct work_struct bio_work;
+ struct rcu_head rcu_head;
+ struct gendisk *disk;
+};
+
+/*
+ * Zone write plug flags bits:
+ * - BLK_ZONE_WPLUG_PLUGGED: Indicate that the zone write plug is plugged,
+ * that is, that write BIOs are being throttled due to a write BIO already
+ * being executed or the zone write plug bio list is not empty.
+ * - BLK_ZONE_WPLUG_ERROR: Indicate that a write error happened which will be
+ * recovered with a report zone to update the zone write pointer offset.
+ * - BLK_ZONE_WPLUG_UNHASHED: Indicates that the zone write plug was removed
+ * from the disk hash table and that the initial reference to the zone
+ * write plug set when the plug was first added to the hash table has been
+ * dropped. This flag is set when a zone is reset, finished or become full,
+ * to prevent new references to the zone write plug to be taken for
+ * newly incoming BIOs. A zone write plug flagged with this flag will be
+ * freed once all remaining references from BIOs or functions are dropped.
+ */
+#define BLK_ZONE_WPLUG_PLUGGED (1U << 0)
+#define BLK_ZONE_WPLUG_ERROR (1U << 1)
+#define BLK_ZONE_WPLUG_UNHASHED (1U << 2)
+
+#define BLK_ZONE_WPLUG_BUSY (BLK_ZONE_WPLUG_PLUGGED | BLK_ZONE_WPLUG_ERROR)
+
/**
* blk_zone_cond_str - Return string XXX in BLK_ZONE_COND_XXX.
* @zone_cond: BLK_ZONE_COND_XXX.
@@ -425,12 +487,1027 @@ int blkdev_zone_mgmt_ioctl(struct block_device *bdev, blk_mode_t mode,
return ret;
}
-void disk_free_zone_bitmaps(struct gendisk *disk)
+static inline bool disk_zone_is_conv(struct gendisk *disk, sector_t sector)
+{
+ if (!disk->conv_zones_bitmap)
+ return false;
+ return test_bit(disk_zone_no(disk, sector), disk->conv_zones_bitmap);
+}
+
+static inline bool bio_zone_is_conv(struct bio *bio)
+{
+ return disk_zone_is_conv(bio->bi_bdev->bd_disk, bio->bi_iter.bi_sector);
+}
+
+static bool disk_insert_zone_wplug(struct gendisk *disk,
+ struct blk_zone_wplug *zwplug)
+{
+ struct blk_zone_wplug *zwplg;
+ unsigned long flags;
+ unsigned int idx =
+ hash_32(zwplug->zone_no, disk->zone_wplugs_hash_bits);
+
+ /*
+ * Add the new zone write plug to the hash table, but carefully as we
+ * are racing with other submission context, so we may already have a
+ * zone write plug for the same zone.
+ */
+ spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
+ hlist_for_each_entry_rcu(zwplg, &disk->zone_wplugs_hash[idx], node) {
+ if (zwplg->zone_no == zwplug->zone_no) {
+ spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
+ return false;
+ }
+ }
+ hlist_add_head_rcu(&zwplug->node, &disk->zone_wplugs_hash[idx]);
+ spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
+
+ return true;
+}
+
+static void disk_remove_zone_wplug(struct gendisk *disk,
+ struct blk_zone_wplug *zwplug)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
+ zwplug->flags |= BLK_ZONE_WPLUG_UNHASHED;
+ atomic_dec(&zwplug->ref);
+ hlist_del_init_rcu(&zwplug->node);
+ spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
+}
+
+static inline bool disk_should_remove_zone_wplug(struct gendisk *disk,
+ struct blk_zone_wplug *zwplug)
+{
+ /* If the zone is still busy, the plug cannot be removed. */
+ if (zwplug->flags & BLK_ZONE_WPLUG_BUSY)
+ return false;
+
+ /* We can remove zone write plugs for zones that are empty or full. */
+ return !zwplug->wp_offset ||
+ zwplug->wp_offset >= disk->zone_capacity;
+}
+
+static inline struct blk_zone_wplug *
+disk_lookup_zone_wplug(struct gendisk *disk, sector_t sector)
+{
+ unsigned int zno = disk_zone_no(disk, sector);
+ unsigned int idx = hash_32(zno, disk->zone_wplugs_hash_bits);
+ struct blk_zone_wplug *zwplug;
+
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(zwplug, &disk->zone_wplugs_hash[idx], node) {
+ if (zwplug->zone_no == zno)
+ goto unlock;
+ }
+ zwplug = NULL;
+
+unlock:
+ rcu_read_unlock();
+ return zwplug;
+}
+
+static inline struct blk_zone_wplug *bio_lookup_zone_wplug(struct bio *bio)
+{
+ return disk_lookup_zone_wplug(bio->bi_bdev->bd_disk,
+ bio->bi_iter.bi_sector);
+}
+
+static inline void blk_get_zone_wplug(struct blk_zone_wplug *zwplug)
+{
+ atomic_inc(&zwplug->ref);
+}
+
+static struct blk_zone_wplug *disk_get_zone_wplug(struct gendisk *disk,
+ sector_t sector)
+{
+ struct blk_zone_wplug *zwplug;
+
+ rcu_read_lock();
+ zwplug = disk_lookup_zone_wplug(disk, sector);
+ if (zwplug && !atomic_inc_not_zero(&zwplug->ref))
+ zwplug = NULL;
+ rcu_read_unlock();
+
+ return zwplug;
+}
+
+static void disk_free_zone_wplug_rcu(struct rcu_head *rcu_head)
+{
+ struct blk_zone_wplug *zwplug =
+ container_of(rcu_head, struct blk_zone_wplug, rcu_head);
+
+ mempool_free(zwplug, zwplug->disk->zone_wplugs_pool);
+}
+
+static inline void disk_put_zone_wplug(struct blk_zone_wplug *zwplug)
+{
+ if (atomic_dec_and_test(&zwplug->ref)) {
+ WARN_ON_ONCE(!bio_list_empty(&zwplug->bio_list));
+ WARN_ON_ONCE(!list_empty(&zwplug->link));
+
+ call_rcu(&zwplug->rcu_head, disk_free_zone_wplug_rcu);
+ }
+}
+
+static void blk_zone_wplug_bio_work(struct work_struct *work);
+
+/*
+ * Get a reference on the write plug for the zone containing @sector.
+ * If the plug does not exist, it is allocated and hashed.
+ * Return a pointer to the zone write plug with the plug spinlock held.
+ */
+static struct blk_zone_wplug *disk_get_and_lock_zone_wplug(struct gendisk *disk,
+ sector_t sector, gfp_t gfp_mask,
+ unsigned long *flags)
+{
+ unsigned int zno = disk_zone_no(disk, sector);
+ struct blk_zone_wplug *zwplug;
+
+again:
+ zwplug = disk_get_zone_wplug(disk, sector);
+ if (zwplug) {
+ /*
+ * Check that a BIO completion or a zone reset or finish
+ * operation has not already removed the zone write plug from
+ * the hash table and dropped its reference count. In such case,
+ * we need to get a new plug so start over from the beginning.
+ */
+ spin_lock_irqsave(&zwplug->lock, *flags);
+ if (zwplug->flags & BLK_ZONE_WPLUG_UNHASHED) {
+ spin_unlock_irqrestore(&zwplug->lock, *flags);
+ disk_put_zone_wplug(zwplug);
+ goto again;
+ }
+ return zwplug;
+ }
+
+ /*
+ * Allocate and initialize a zone write plug with an extra reference
+ * so that it is not freed when the zone write plug becomes idle without
+ * the zone being full.
+ */
+ zwplug = mempool_alloc(disk->zone_wplugs_pool, gfp_mask);
+ if (!zwplug)
+ return NULL;
+
+ INIT_HLIST_NODE(&zwplug->node);
+ INIT_LIST_HEAD(&zwplug->link);
+ atomic_set(&zwplug->ref, 2);
+ spin_lock_init(&zwplug->lock);
+ zwplug->flags = 0;
+ zwplug->zone_no = zno;
+ zwplug->wp_offset = sector & (disk->queue->limits.chunk_sectors - 1);
+ bio_list_init(&zwplug->bio_list);
+ INIT_WORK(&zwplug->bio_work, blk_zone_wplug_bio_work);
+ zwplug->disk = disk;
+
+ spin_lock_irqsave(&zwplug->lock, *flags);
+
+ /*
+ * Insert the new zone write plug in the hash table. This can fail only
+ * if another context already inserted a plug. Retry from the beginning
+ * in such case.
+ */
+ if (!disk_insert_zone_wplug(disk, zwplug)) {
+ spin_unlock_irqrestore(&zwplug->lock, *flags);
+ mempool_free(zwplug, disk->zone_wplugs_pool);
+ goto again;
+ }
+
+ return zwplug;
+}
+
+static struct blk_zone_wplug *bio_get_and_lock_zone_wplug(struct bio *bio,
+ unsigned long *flags)
+{
+ gfp_t gfp_mask;
+
+ if (bio->bi_opf & REQ_NOWAIT)
+ gfp_mask = GFP_NOWAIT;
+ else
+ gfp_mask = GFP_NOIO;
+
+ return disk_get_and_lock_zone_wplug(bio->bi_bdev->bd_disk,
+ bio->bi_iter.bi_sector, gfp_mask, flags);
+}
+
+static inline void blk_zone_wplug_bio_io_error(struct bio *bio)
+{
+ struct request_queue *q = bio->bi_bdev->bd_disk->queue;
+
+ bio_clear_flag(bio, BIO_ZONE_WRITE_PLUGGING);
+ bio_io_error(bio);
+ blk_queue_exit(q);
+}
+
+/*
+ * Abort (fail) all plugged BIOs of a zone write plug.
+ */
+static void disk_zone_wplug_abort(struct blk_zone_wplug *zwplug)
+{
+ struct bio *bio;
+
+ while ((bio = bio_list_pop(&zwplug->bio_list))) {
+ blk_zone_wplug_bio_io_error(bio);
+ disk_put_zone_wplug(zwplug);
+ }
+}
+
+/*
+ * Abort (fail) all plugged BIOs of a zone write plug that are not aligned
+ * with the assumed write pointer location of the zone when the BIO will
+ * be unplugged.
+ */
+static void disk_zone_wplug_abort_unaligned(struct gendisk *disk,
+ struct blk_zone_wplug *zwplug)
+{
+ unsigned int zone_capacity = disk->zone_capacity;
+ unsigned int wp_offset = zwplug->wp_offset;
+ struct bio_list bl = BIO_EMPTY_LIST;
+ struct bio *bio;
+
+ while ((bio = bio_list_pop(&zwplug->bio_list))) {
+ if (wp_offset >= zone_capacity ||
+ bio_offset_from_zone_start(bio) != wp_offset) {
+ blk_zone_wplug_bio_io_error(bio);
+ disk_put_zone_wplug(zwplug);
+ continue;
+ }
+
+ wp_offset += bio_sectors(bio);
+ bio_list_add(&bl, bio);
+ }
+
+ bio_list_merge(&zwplug->bio_list, &bl);
+}
+
+/*
+ * Set a zone write plug write pointer offset to either 0 (zone reset case)
+ * or to the zone size (zone finish case). This aborts all plugged BIOs, which
+ * is fine to do as doing a zone reset or zone finish while writes are in-flight
+ * is a mistake from the user which will most likely cause all plugged BIOs to
+ * fail anyway.
+ */
+static void disk_zone_wplug_set_wp_offset(struct gendisk *disk,
+ struct blk_zone_wplug *zwplug,
+ unsigned int wp_offset)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&zwplug->lock, flags);
+
+ /*
+ * Make sure that a BIO completion or another zone reset or finish
+ * operation has not already removed the plug from the hash table.
+ */
+ if (zwplug->flags & BLK_ZONE_WPLUG_UNHASHED) {
+ spin_unlock_irqrestore(&zwplug->lock, flags);
+ return;
+ }
+
+ /* Update the zone write pointer and abort all plugged BIOs. */
+ zwplug->wp_offset = wp_offset;
+ disk_zone_wplug_abort(zwplug);
+
+ /*
+ * Updating the write pointer offset puts back the zone
+ * in a good state. So clear the error flag and decrement the
+ * error count if we were in error state.
+ */
+ if (zwplug->flags & BLK_ZONE_WPLUG_ERROR) {
+ zwplug->flags &= ~BLK_ZONE_WPLUG_ERROR;
+ spin_lock(&disk->zone_wplugs_lock);
+ list_del_init(&zwplug->link);
+ spin_unlock(&disk->zone_wplugs_lock);
+ }
+
+ /*
+ * The zone write plug now has no BIO plugged: remove it from the
+ * hash table so that it cannot be seen. The plug will be freed
+ * when the last reference is dropped.
+ */
+ if (disk_should_remove_zone_wplug(disk, zwplug))
+ disk_remove_zone_wplug(disk, zwplug);
+
+ spin_unlock_irqrestore(&zwplug->lock, flags);
+}
+
+static bool blk_zone_wplug_handle_reset_or_finish(struct bio *bio,
+ unsigned int wp_offset)
+{
+ struct gendisk *disk = bio->bi_bdev->bd_disk;
+ struct blk_zone_wplug *zwplug;
+
+ /* Conventional zones cannot be reset nor finished. */
+ if (bio_zone_is_conv(bio)) {
+ bio_io_error(bio);
+ return true;
+ }
+
+ /*
+ * If we have a zone write plug, set its write pointer offset to 0
+ * (reset case) or to the zone size (finish case). This will abort all
+ * BIOs plugged for the target zone. It is fine as resetting or
+ * finishing zones while writes are still in-flight will result in the
+ * writes failing anyway.
+ */
+ zwplug = disk_get_zone_wplug(disk, bio->bi_iter.bi_sector);
+ if (zwplug) {
+ disk_zone_wplug_set_wp_offset(disk, zwplug, wp_offset);
+ disk_put_zone_wplug(zwplug);
+ }
+
+ return false;
+}
+
+static bool blk_zone_wplug_handle_reset_all(struct bio *bio)
+{
+ struct gendisk *disk = bio->bi_bdev->bd_disk;
+ struct blk_zone_wplug *zwplug;
+ sector_t sector;
+
+ /*
+ * Set the write pointer offset of all zone write plugs to 0. This will
+ * abort all plugged BIOs. It is fine as resetting zones while writes
+ * are still in-flight will result in the writes failing anyway.
+ */
+ for (sector = 0; sector < get_capacity(disk);
+ sector += disk->queue->limits.chunk_sectors) {
+ zwplug = disk_get_zone_wplug(disk, sector);
+ if (zwplug) {
+ disk_zone_wplug_set_wp_offset(disk, zwplug, 0);
+ disk_put_zone_wplug(zwplug);
+ }
+ }
+
+ return false;
+}
+
+static inline void blk_zone_wplug_add_bio(struct blk_zone_wplug *zwplug,
+ struct bio *bio, unsigned int nr_segs)
+{
+ /*
+ * Grab an extra reference on the BIO request queue usage counter.
+ * This reference will be reused to submit a request for the BIO for
+ * blk-mq devices and dropped when the BIO is failed and after
+ * it is issued in the case of BIO-based devices.
+ */
+ percpu_ref_get(&bio->bi_bdev->bd_disk->queue->q_usage_counter);
+
+ /*
+ * The BIO is being plugged and thus will have to wait for the on-going
+ * write and for all other writes already plugged. So polling makes
+ * no sense.
+ */
+ bio_clear_polled(bio);
+
+ /*
+ * Reuse the poll cookie field to store the number of segments when
+ * split to the hardware limits.
+ */
+ bio->__bi_nr_segments = nr_segs;
+
+ /*
+ * We always receive BIOs after they are split and ready to be issued.
+ * The block layer passes the parts of a split BIO in order, and the
+ * user must also issue write sequentially. So simply add the new BIO
+ * at the tail of the list to preserve the sequential write order.
+ */
+ bio_list_add(&zwplug->bio_list, bio);
+}
+
+/*
+ * Called from bio_attempt_back_merge() when a BIO was merged with a request.
+ */
+void blk_zone_write_plug_bio_merged(struct bio *bio)
+{
+ struct blk_zone_wplug *zwplug;
+ unsigned long flags;
+
+ /*
+ * If the BIO was already plugged, then we were called through
+ * blk_zone_write_plug_attempt_merge() -> blk_attempt_bio_merge().
+ * For this case, blk_zone_write_plug_attempt_merge() will handle the
+ * zone write pointer offset update.
+ */
+ if (bio_flagged(bio, BIO_ZONE_WRITE_PLUGGING))
+ return;
+
See? you have to check anyway ...
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Ivo Totev, Andrew McDonald,
Werner Knoblich
