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Merge branch 'for-4.12/block' of git://git.kernel.dk/linux-block

Browse source 
Pull block layer updates from Jens Axboe:

 - Add BFQ IO scheduler under the new blk-mq scheduling framework. BFQ
   was initially a fork of CFQ, but subsequently changed to implement
   fairness based on B-WF2Q+, a modified variant of WF2Q. BFQ is meant
   to be used on desktop type single drives, providing good fairness.
   From Paolo.

 - Add Kyber IO scheduler. This is a full multiqueue aware scheduler,
   using a scalable token based algorithm that throttles IO based on
   live completion IO stats, similary to blk-wbt. From Omar.

 - A series from Jan, moving users to separately allocated backing
   devices. This continues the work of separating backing device life
   times, solving various problems with hot removal.

 - A series of updates for lightnvm, mostly from Javier. Includes a
   'pblk' target that exposes an open channel SSD as a physical block
   device.

 - A series of fixes and improvements for nbd from Josef.

 - A series from Omar, removing queue sharing between devices on mostly
   legacy drivers. This helps us clean up other bits, if we know that a
   queue only has a single device backing. This has been overdue for
   more than a decade.

 - Fixes for the blk-stats, and improvements to unify the stats and user
   windows. This both improves blk-wbt, and enables other users to
   register a need to receive IO stats for a device. From Omar.

 - blk-throttle improvements from Shaohua. This provides a scalable
   framework for implementing scalable priotization - particularly for
   blk-mq, but applicable to any type of block device. The interface is
   marked experimental for now.

 - Bucketized IO stats for IO polling from Stephen Bates. This improves
   efficiency of polled workloads in the presence of mixed block size
   IO.

 - A few fixes for opal, from Scott.

 - A few pulls for NVMe, including a lot of fixes for NVMe-over-fabrics.
   From a variety of folks, mostly Sagi and James Smart.

 - A series from Bart, improving our exposed info and capabilities from
   the blk-mq debugfs support.

 - A series from Christoph, cleaning up how handle WRITE_ZEROES.

 - A series from Christoph, cleaning up the block layer handling of how
   we track errors in a request. On top of being a nice cleanup, it also
   shrinks the size of struct request a bit.

 - Removal of mg_disk and hd (sorry Linus) by Christoph. The former was
   never used by platforms, and the latter has outlived it's usefulness.

 - Various little bug fixes and cleanups from a wide variety of folks.

* 'for-4.12/block' of git://git.kernel.dk/linux-block: (329 commits)
  block: hide badblocks attribute by default
  blk-mq: unify hctx delay_work and run_work
  block: add kblock_mod_delayed_work_on()
  blk-mq: unify hctx delayed_run_work and run_work
  nbd: fix use after free on module unload
  MAINTAINERS: bfq: Add Paolo as maintainer for the BFQ I/O scheduler
  blk-mq-sched: alloate reserved tags out of normal pool
  mtip32xx: use runtime tag to initialize command header
  scsi: Implement blk_mq_ops.show_rq()
  blk-mq: Add blk_mq_ops.show_rq()
  blk-mq: Show operation, cmd_flags and rq_flags names
  blk-mq: Make blk_flags_show() callers append a newline character
  blk-mq: Move the "state" debugfs attribute one level down
  blk-mq: Unregister debugfs attributes earlier
  blk-mq: Only unregister hctxs for which registration succeeded
  blk-mq-debugfs: Rename functions for registering and unregistering the mq directory
  blk-mq: Let blk_mq_debugfs_register() look up the queue name
  blk-mq: Register <dev>/queue/mq after having registered <dev>/queue
  ide-pm: always pass 0 error to ide_complete_rq in ide_do_devset
  ide-pm: always pass 0 error to __blk_end_request_all
  ..
This commit is contained in:
Linus Torvalds 2017-05-01 10:39:57 -07:00
commit 694752922b
255 changed files with 24643 additions and 6152 deletions
Download patch file Download diff file Expand all files Collapse all files

1
drivers/md/dm-cache-target.c
View file

@ -2773,7 +2773,6 @@ static int cache_create(struct cache_args *ca, struct cache **result)
ti->num_discard_bios = 1;
ti->discards_supported = true;
ti->discard_zeroes_data_unsupported = true;
ti->split_discard_bios = false;
cache->features = ca->features;

1
drivers/md/dm-core.h
View file

@ -132,6 +132,7 @@ void dm_init_md_queue(struct mapped_device *md);
void dm_init_normal_md_queue(struct mapped_device *md);
int md_in_flight(struct mapped_device *md);
void disable_write_same(struct mapped_device *md);
void disable_write_zeroes(struct mapped_device *md);
static inline struct completion *dm_get_completion_from_kobject(struct kobject *kobj)
{

1
drivers/md/dm-crypt.c
View file

@ -2030,7 +2030,6 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
wake_up_process(cc->write_thread);
ti->num_flush_bios = 1;
ti->discard_zeroes_data_unsupported = true;
return 0;

18
drivers/md/dm-io.c
View file

@ -312,9 +312,12 @@ static void do_region(int op, int op_flags, unsigned region,
*/
if (op == REQ_OP_DISCARD)
special_cmd_max_sectors = q->limits.max_discard_sectors;
else if (op == REQ_OP_WRITE_ZEROES)
special_cmd_max_sectors = q->limits.max_write_zeroes_sectors;
else if (op == REQ_OP_WRITE_SAME)
special_cmd_max_sectors = q->limits.max_write_same_sectors;
if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_SAME) &&
if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES ||
op == REQ_OP_WRITE_SAME) &&
special_cmd_max_sectors == 0) {
dec_count(io, region, -EOPNOTSUPP);
return;
@ -328,11 +331,18 @@ static void do_region(int op, int op_flags, unsigned region,
/*
* Allocate a suitably sized-bio.
*/
if ((op == REQ_OP_DISCARD) || (op == REQ_OP_WRITE_SAME))
switch (op) {
case REQ_OP_DISCARD:
case REQ_OP_WRITE_ZEROES:
num_bvecs = 0;
break;
case REQ_OP_WRITE_SAME:
num_bvecs = 1;
else
break;
default:
num_bvecs = min_t(int, BIO_MAX_PAGES,
dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
}
bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
bio->bi_iter.bi_sector = where->sector + (where->count - remaining);
@ -341,7 +351,7 @@ static void do_region(int op, int op_flags, unsigned region,
bio_set_op_attrs(bio, op, op_flags);
store_io_and_region_in_bio(bio, io, region);
if (op == REQ_OP_DISCARD) {
if (op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES) {
num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
remaining -= num_sectors;

6
drivers/md/dm-kcopyd.c
View file

@ -733,11 +733,11 @@ int dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
job->pages = &zero_page_list;
/*
* Use WRITE SAME to optimize zeroing if all dests support it.
* Use WRITE ZEROES to optimize zeroing if all dests support it.
*/
job->rw = REQ_OP_WRITE_SAME;
job->rw = REQ_OP_WRITE_ZEROES;
for (i = 0; i < job->num_dests; i++)
if (!bdev_write_same(job->dests[i].bdev)) {
if (!bdev_write_zeroes_sectors(job->dests[i].bdev)) {
job->rw = WRITE;
break;
}

1
drivers/md/dm-linear.c
View file

@ -59,6 +59,7 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->num_flush_bios = 1;
ti->num_discard_bios = 1;
ti->num_write_same_bios = 1;
ti->num_write_zeroes_bios = 1;
ti->private = lc;
return 0;

3
drivers/md/dm-mpath.c
View file

@ -1103,6 +1103,7 @@ static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
ti->num_flush_bios = 1;
ti->num_discard_bios = 1;
ti->num_write_same_bios = 1;
ti->num_write_zeroes_bios = 1;
if (m->queue_mode == DM_TYPE_BIO_BASED)
ti->per_io_data_size = multipath_per_bio_data_size();
else
@ -1491,7 +1492,7 @@ static int do_end_io(struct multipath *m, struct request *clone,
*/
int r = DM_ENDIO_REQUEUE;
if (!error && !clone->errors)
if (!error)
return 0; /* I/O complete */
if (noretry_error(error))

6
drivers/md/dm-raid.c
View file

@ -2813,7 +2813,9 @@ static void configure_discard_support(struct raid_set *rs)
/* Assume discards not supported until after checks below. */
ti->discards_supported = false;
/* RAID level 4,5,6 require discard_zeroes_data for data integrity! */
/*
* XXX: RAID level 4,5,6 require zeroing for safety.
*/
raid456 = (rs->md.level == 4 || rs->md.level == 5 || rs->md.level == 6);
for (i = 0; i < rs->raid_disks; i++) {
@ -2827,8 +2829,6 @@ static void configure_discard_support(struct raid_set *rs)
return;
if (raid456) {
if (!q->limits.discard_zeroes_data)
return;
if (!devices_handle_discard_safely) {
DMERR("raid456 discard support disabled due to discard_zeroes_data uncertainty.");
DMERR("Set dm-raid.devices_handle_discard_safely=Y to override.");

1
drivers/md/dm-raid1.c
View file

@ -1124,7 +1124,6 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->num_flush_bios = 1;
ti->num_discard_bios = 1;
ti->per_io_data_size = sizeof(struct dm_raid1_bio_record);
ti->discard_zeroes_data_unsupported = true;
ms->kmirrord_wq = alloc_workqueue("kmirrord", WQ_MEM_RECLAIM, 0);
if (!ms->kmirrord_wq) {

15
drivers/md/dm-rq.c
View file

@ -298,9 +298,14 @@ static void dm_done(struct request *clone, int error, bool mapped)
r = rq_end_io(tio->ti, clone, error, &tio->info);
}
if (unlikely(r == -EREMOTEIO && (req_op(clone) == REQ_OP_WRITE_SAME) &&
!clone->q->limits.max_write_same_sectors))
disable_write_same(tio->md);
if (unlikely(r == -EREMOTEIO)) {
if (req_op(clone) == REQ_OP_WRITE_SAME &&
!clone->q->limits.max_write_same_sectors)
disable_write_same(tio->md);
if (req_op(clone) == REQ_OP_WRITE_ZEROES &&
!clone->q->limits.max_write_zeroes_sectors)
disable_write_zeroes(tio->md);
}
if (r <= 0)
/* The target wants to complete the I/O */
@ -358,7 +363,7 @@ static void dm_complete_request(struct request *rq, int error)
if (!rq->q->mq_ops)
blk_complete_request(rq);
else
blk_mq_complete_request(rq, error);
blk_mq_complete_request(rq);
}
/*
@ -762,7 +767,7 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
return BLK_MQ_RQ_QUEUE_OK;
}
static struct blk_mq_ops dm_mq_ops = {
static const struct blk_mq_ops dm_mq_ops = {
.queue_rq = dm_mq_queue_rq,
.complete = dm_softirq_done,
.init_request = dm_mq_init_request,

2
drivers/md/dm-stripe.c
View file

@ -169,6 +169,7 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->num_flush_bios = stripes;
ti->num_discard_bios = stripes;
ti->num_write_same_bios = stripes;
ti->num_write_zeroes_bios = stripes;
sc->chunk_size = chunk_size;
if (chunk_size & (chunk_size - 1))
@ -293,6 +294,7 @@ static int stripe_map(struct dm_target *ti, struct bio *bio)
return DM_MAPIO_REMAPPED;
}
if (unlikely(bio_op(bio) == REQ_OP_DISCARD) ||
unlikely(bio_op(bio) == REQ_OP_WRITE_ZEROES) ||
unlikely(bio_op(bio) == REQ_OP_WRITE_SAME)) {
target_bio_nr = dm_bio_get_target_bio_nr(bio);
BUG_ON(target_bio_nr >= sc->stripes);

49
drivers/md/dm-table.c
View file

@ -1449,22 +1449,6 @@ static bool dm_table_supports_flush(struct dm_table *t, unsigned long flush)
return false;
}
static bool dm_table_discard_zeroes_data(struct dm_table *t)
{
struct dm_target *ti;
unsigned i = 0;
/* Ensure that all targets supports discard_zeroes_data. */
while (i < dm_table_get_num_targets(t)) {
ti = dm_table_get_target(t, i++);
if (ti->discard_zeroes_data_unsupported)
return false;
}
return true;
}
static int device_is_nonrot(struct dm_target *ti, struct dm_dev *dev,
sector_t start, sector_t len, void *data)
{
@ -1533,6 +1517,34 @@ static bool dm_table_supports_write_same(struct dm_table *t)
return true;
}
static int device_not_write_zeroes_capable(struct dm_target *ti, struct dm_dev *dev,
sector_t start, sector_t len, void *data)
{
struct request_queue *q = bdev_get_queue(dev->bdev);
return q && !q->limits.max_write_zeroes_sectors;
}
static bool dm_table_supports_write_zeroes(struct dm_table *t)
{
struct dm_target *ti;
unsigned i = 0;
while (i < dm_table_get_num_targets(t)) {
ti = dm_table_get_target(t, i++);
if (!ti->num_write_zeroes_bios)
return false;
if (!ti->type->iterate_devices ||
ti->type->iterate_devices(ti, device_not_write_zeroes_capable, NULL))
return false;
}
return true;
}
static int device_discard_capable(struct dm_target *ti, struct dm_dev *dev,
sector_t start, sector_t len, void *data)
{
@ -1592,9 +1604,6 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
}
blk_queue_write_cache(q, wc, fua);
if (!dm_table_discard_zeroes_data(t))
q->limits.discard_zeroes_data = 0;
/* Ensure that all underlying devices are non-rotational. */
if (dm_table_all_devices_attribute(t, device_is_nonrot))
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);
@ -1603,6 +1612,8 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
if (!dm_table_supports_write_same(t))
q->limits.max_write_same_sectors = 0;
if (!dm_table_supports_write_zeroes(t))
q->limits.max_write_zeroes_sectors = 0;
if (dm_table_all_devices_attribute(t, queue_supports_sg_merge))
queue_flag_clear_unlocked(QUEUE_FLAG_NO_SG_MERGE, q);

2
drivers/md/dm-thin.c
View file

@ -3263,7 +3263,6 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
* them down to the data device. The thin device's discard
* processing will cause mappings to be removed from the btree.
*/
ti->discard_zeroes_data_unsupported = true;
if (pf.discard_enabled && pf.discard_passdown) {
ti->num_discard_bios = 1;
@ -4119,7 +4118,6 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
ti->per_io_data_size = sizeof(struct dm_thin_endio_hook);
/* In case the pool supports discards, pass them on. */
ti->discard_zeroes_data_unsupported = true;
if (tc->pool->pf.discard_enabled) {
ti->discards_supported = true;
ti->num_discard_bios = 1;

32
drivers/md/dm.c
View file

@ -810,7 +810,6 @@ static void dec_pending(struct dm_io *io, int error)
queue_io(md, bio);
} else {
/* done with normal IO or empty flush */
trace_block_bio_complete(md->queue, bio, io_error);
bio->bi_error = io_error;
bio_endio(bio);
}
@ -825,6 +824,14 @@ void disable_write_same(struct mapped_device *md)
limits->max_write_same_sectors = 0;
}
void disable_write_zeroes(struct mapped_device *md)
{
struct queue_limits *limits = dm_get_queue_limits(md);
/* device doesn't really support WRITE ZEROES, disable it */
limits->max_write_zeroes_sectors = 0;
}
static void clone_endio(struct bio *bio)
{
int error = bio->bi_error;
@ -851,9 +858,14 @@ static void clone_endio(struct bio *bio)
}
}
if (unlikely(r == -EREMOTEIO && (bio_op(bio) == REQ_OP_WRITE_SAME) &&
!bdev_get_queue(bio->bi_bdev)->limits.max_write_same_sectors))
disable_write_same(md);
if (unlikely(r == -EREMOTEIO)) {
if (bio_op(bio) == REQ_OP_WRITE_SAME &&
!bdev_get_queue(bio->bi_bdev)->limits.max_write_same_sectors)
disable_write_same(md);
if (bio_op(bio) == REQ_OP_WRITE_ZEROES &&
!bdev_get_queue(bio->bi_bdev)->limits.max_write_zeroes_sectors)
disable_write_zeroes(md);
}
free_tio(tio);
dec_pending(io, error);
@ -1202,6 +1214,11 @@ static unsigned get_num_write_same_bios(struct dm_target *ti)
return ti->num_write_same_bios;
}
static unsigned get_num_write_zeroes_bios(struct dm_target *ti)
{
return ti->num_write_zeroes_bios;
}
typedef bool (*is_split_required_fn)(struct dm_target *ti);
static bool is_split_required_for_discard(struct dm_target *ti)
@ -1256,6 +1273,11 @@ static int __send_write_same(struct clone_info *ci)
return __send_changing_extent_only(ci, get_num_write_same_bios, NULL);
}
static int __send_write_zeroes(struct clone_info *ci)
{
return __send_changing_extent_only(ci, get_num_write_zeroes_bios, NULL);
}
/*
* Select the correct strategy for processing a non-flush bio.
*/
@ -1270,6 +1292,8 @@ static int __split_and_process_non_flush(struct clone_info *ci)
return __send_discard(ci);
else if (unlikely(bio_op(bio) == REQ_OP_WRITE_SAME))
return __send_write_same(ci);
else if (unlikely(bio_op(bio) == REQ_OP_WRITE_ZEROES))
return __send_write_zeroes(ci);
ti = dm_table_find_target(ci->map, ci->sector);
if (!dm_target_is_valid(ti))

1
drivers/md/linear.c
View file

@ -293,6 +293,7 @@ static void linear_make_request(struct mddev *mddev, struct bio *bio)
split, disk_devt(mddev->gendisk),
bio_sector);
mddev_check_writesame(mddev, split);
mddev_check_write_zeroes(mddev, split);
generic_make_request(split);
}
} while (split != bio);

7
drivers/md/md.h
View file

@ -709,4 +709,11 @@ static inline void mddev_check_writesame(struct mddev *mddev, struct bio *bio)
!bdev_get_queue(bio->bi_bdev)->limits.max_write_same_sectors)
mddev->queue->limits.max_write_same_sectors = 0;
}
static inline void mddev_check_write_zeroes(struct mddev *mddev, struct bio *bio)
{
if (bio_op(bio) == REQ_OP_WRITE_ZEROES &&
!bdev_get_queue(bio->bi_bdev)->limits.max_write_zeroes_sectors)
mddev->queue->limits.max_write_zeroes_sectors = 0;
}
#endif /* _MD_MD_H */

1
drivers/md/multipath.c
View file

@ -139,6 +139,7 @@ static void multipath_make_request(struct mddev *mddev, struct bio * bio)
mp_bh->bio.bi_end_io = multipath_end_request;
mp_bh->bio.bi_private = mp_bh;
mddev_check_writesame(mddev, &mp_bh->bio);
mddev_check_write_zeroes(mddev, &mp_bh->bio);
generic_make_request(&mp_bh->bio);
return;
}

2
drivers/md/raid0.c
View file

@ -383,6 +383,7 @@ static int raid0_run(struct mddev *mddev)
blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
blk_queue_max_write_same_sectors(mddev->queue, mddev->chunk_sectors);
blk_queue_max_write_zeroes_sectors(mddev->queue, mddev->chunk_sectors);
blk_queue_max_discard_sectors(mddev->queue, mddev->chunk_sectors);
blk_queue_io_min(mddev->queue, mddev->chunk_sectors << 9);
@ -504,6 +505,7 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
split, disk_devt(mddev->gendisk),
bio_sector);
mddev_check_writesame(mddev, split);
mddev_check_write_zeroes(mddev, split);
generic_make_request(split);
}
} while (split != bio);

4
drivers/md/raid1.c
View file

@ -3177,8 +3177,10 @@ static int raid1_run(struct mddev *mddev)
if (IS_ERR(conf))
return PTR_ERR(conf);
if (mddev->queue)
if (mddev->queue) {
blk_queue_max_write_same_sectors(mddev->queue, 0);
blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
}
rdev_for_each(rdev, mddev) {
if (!mddev->gendisk)

1
drivers/md/raid10.c
View file

@ -3749,6 +3749,7 @@ static int raid10_run(struct mddev *mddev)
blk_queue_max_discard_sectors(mddev->queue,
mddev->chunk_sectors);
blk_queue_max_write_same_sectors(mddev->queue, 0);
blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
blk_queue_io_min(mddev->queue, chunk_size);
if (conf->geo.raid_disks % conf->geo.near_copies)
blk_queue_io_opt(mddev->queue, chunk_size * conf->geo.raid_disks);

53
drivers/md/raid5.c
View file

@ -5031,8 +5031,6 @@ static void raid5_align_endio(struct bio *bi)
rdev_dec_pending(rdev, conf->mddev);
if (!error) {
trace_block_bio_complete(bdev_get_queue(raid_bi->bi_bdev),
raid_bi, 0);
bio_endio(raid_bi);
if (atomic_dec_and_test(&conf->active_aligned_reads))
wake_up(&conf->wait_for_quiescent);
@ -7229,7 +7227,6 @@ static int raid5_run(struct mddev *mddev)
if (mddev->queue) {
int chunk_size;
bool discard_supported = true;
/* read-ahead size must cover two whole stripes, which
* is 2 * (datadisks) * chunksize where 'n' is the
* number of raid devices
@ -7265,48 +7262,32 @@ static int raid5_run(struct mddev *mddev)
blk_queue_max_discard_sectors(mddev->queue,
0xfffe * STRIPE_SECTORS);
/*
* unaligned part of discard request will be ignored, so can't
* guarantee discard_zeroes_data
*/
mddev->queue->limits.discard_zeroes_data = 0;
blk_queue_max_write_same_sectors(mddev->queue, 0);
blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
rdev_for_each(rdev, mddev) {
disk_stack_limits(mddev->gendisk, rdev->bdev,
rdev->data_offset << 9);
disk_stack_limits(mddev->gendisk, rdev->bdev,
rdev->new_data_offset << 9);
/*
* discard_zeroes_data is required, otherwise data
* could be lost. Consider a scenario: discard a stripe
* (the stripe could be inconsistent if
* discard_zeroes_data is 0); write one disk of the
* stripe (the stripe could be inconsistent again
* depending on which disks are used to calculate
* parity); the disk is broken; The stripe data of this
* disk is lost.
*/
if (!blk_queue_discard(bdev_get_queue(rdev->bdev)) ||
!bdev_get_queue(rdev->bdev)->
limits.discard_zeroes_data)
discard_supported = false;
/* Unfortunately, discard_zeroes_data is not currently
* a guarantee - just a hint. So we only allow DISCARD
* if the sysadmin has confirmed that only safe devices
* are in use by setting a module parameter.
*/
if (!devices_handle_discard_safely) {
if (discard_supported) {
pr_info("md/raid456: discard support disabled due to uncertainty.\n");
pr_info("Set raid456.devices_handle_discard_safely=Y to override.\n");
}
discard_supported = false;
}
}
if (discard_supported &&
/*
* zeroing is required, otherwise data
* could be lost. Consider a scenario: discard a stripe
* (the stripe could be inconsistent if
* discard_zeroes_data is 0); write one disk of the
* stripe (the stripe could be inconsistent again
* depending on which disks are used to calculate
* parity); the disk is broken; The stripe data of this
* disk is lost.
*
* We only allow DISCARD if the sysadmin has confirmed that
* only safe devices are in use by setting a module parameter.
* A better idea might be to turn DISCARD into WRITE_ZEROES
* requests, as that is required to be safe.
*/
if (devices_handle_discard_safely &&
mddev->queue->limits.max_discard_sectors >= (stripe >> 9) &&
mddev->queue->limits.discard_granularity >= stripe)
queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,