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md/raid5: use md_write_start to count stripes, not bios

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We use md_write_start() to increase the count of pending writes, and
md_write_end() to decrement the count.  We currently count bios
submitted to md/raid5.  Change it count stripe_heads that a WRITE bio
has been attached to.

So now, raid5_make_request() calls md_write_start() and then
md_write_end() to keep the count elevated during the setup of the
request.

add_stripe_bio() calls md_write_start() for each stripe_head, and the
completion routines always call md_write_end(), instead of only
calling it when raid5_dec_bi_active_stripes() returns 0.
make_discard_request also calls md_write_start/end().

The parallel between md_write_{start,end} and use of bi_phys_segments
can be seen in that:
 Whenever we set bi_phys_segments to 1, we now call md_write_start.
 Whenever we increment it on non-read requests with
   raid5_inc_bi_active_stripes(), we now call md_write_start().
 Whenever we decrement bi_phys_segments on non-read requsts with
    raid5_dec_bi_active_stripes(), we now call md_write_end().

This reduces our dependence on keeping a per-bio count of active
stripes in bi_phys_segments.

md_write_inc() is added which parallels md_write_start(), but requires
that a write has already been started, and is certain never to sleep.
This can be used inside a spinlocked region when adding to a write
request.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
This commit is contained in:
NeilBrown 2017-03-15 14:05:12 +11:00 committed by Shaohua Li
parent 48df498daf
commit 497280509f
4 changed files with 32 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
drivers/md/md.c
View File

@ -7907,6 +7907,23 @@ void md_write_start(struct mddev *mddev, struct bio *bi)
}
EXPORT_SYMBOL(md_write_start);
/* md_write_inc can only be called when md_write_start() has
* already been called at least once of the current request.
* It increments the counter and is useful when a single request
* is split into several parts. Each part causes an increment and
* so needs a matching md_write_end().
* Unlike md_write_start(), it is safe to call md_write_inc() inside
* a spinlocked region.
*/
void md_write_inc(struct mddev *mddev, struct bio *bi)
{
if (bio_data_dir(bi) != WRITE)
return;
WARN_ON_ONCE(mddev->in_sync || mddev->ro);
atomic_inc(&mddev->writes_pending);
}
EXPORT_SYMBOL(md_write_inc);
void md_write_end(struct mddev *mddev)
{
if (atomic_dec_and_test(&mddev->writes_pending)) {

1
drivers/md/md.h
View File

@ -648,6 +648,7 @@ extern void md_wakeup_thread(struct md_thread *thread);
extern void md_check_recovery(struct mddev *mddev);
extern void md_reap_sync_thread(struct mddev *mddev);
extern void md_write_start(struct mddev *mddev, struct bio *bi);
extern void md_write_inc(struct mddev *mddev, struct bio *bi);
extern void md_write_end(struct mddev *mddev);
extern void md_done_sync(struct mddev *mddev, int blocks, int ok);
extern void md_error(struct mddev *mddev, struct md_rdev *rdev);

2
drivers/md/raid5-cache.c
View File

@ -318,8 +318,8 @@ r5c_return_dev_pending_writes(struct r5conf *conf, struct r5dev *dev,
while (wbi && wbi->bi_iter.bi_sector <
dev->sector + STRIPE_SECTORS) {
wbi2 = r5_next_bio(wbi, dev->sector);
md_write_end(conf->mddev);
if (!raid5_dec_bi_active_stripes(wbi)) {
md_write_end(conf->mddev);
bio_list_add(return_bi, wbi);
}
wbi = wbi2;

27
drivers/md/raid5.c
View File

@ -3274,6 +3274,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
bi->bi_next = *bip;
*bip = bi;
raid5_inc_bi_active_stripes(bi);
md_write_inc(conf->mddev, bi);
if (forwrite) {
/* check if page is covered */
@ -3397,10 +3398,9 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
bi->bi_error = -EIO;
if (!raid5_dec_bi_active_stripes(bi)) {
md_write_end(conf->mddev);
md_write_end(conf->mddev);
if (!raid5_dec_bi_active_stripes(bi))
bio_list_add(return_bi, bi);
}
bi = nextbi;
}
if (bitmap_end)
@ -3421,10 +3421,9 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
bi->bi_error = -EIO;
if (!raid5_dec_bi_active_stripes(bi)) {
md_write_end(conf->mddev);
md_write_end(conf->mddev);
if (!raid5_dec_bi_active_stripes(bi))
bio_list_add(return_bi, bi);
}
bi = bi2;
}
@ -3781,10 +3780,9 @@ returnbi:
while (wbi && wbi->bi_iter.bi_sector <
dev->sector + STRIPE_SECTORS) {
wbi2 = r5_next_bio(wbi, dev->sector);
if (!raid5_dec_bi_active_stripes(wbi)) {
md_write_end(conf->mddev);
md_write_end(conf->mddev);
if (!raid5_dec_bi_active_stripes(wbi))
bio_list_add(return_bi, wbi);
}
wbi = wbi2;
}
bitmap_endwrite(conf->mddev->bitmap, sh->sector,
@ -5487,6 +5485,7 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
bi->bi_next = NULL;
bi->bi_phys_segments = 1; /* over-loaded to count active stripes */
md_write_start(mddev, bi);
stripe_sectors = conf->chunk_sectors *
(conf->raid_disks - conf->max_degraded);
@ -5533,6 +5532,7 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
sh->dev[d].towrite = bi;
set_bit(R5_OVERWRITE, &sh->dev[d].flags);
raid5_inc_bi_active_stripes(bi);
md_write_inc(mddev, bi);
sh->overwrite_disks++;
}
spin_unlock_irq(&sh->stripe_lock);
@ -5555,9 +5555,9 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
release_stripe_plug(mddev, sh);
}
md_write_end(mddev);
remaining = raid5_dec_bi_active_stripes(bi);
if (remaining == 0) {
md_write_end(mddev);
bio_endio(bi);
}
}
@ -5592,8 +5592,6 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
do_flush = bi->bi_opf & REQ_PREFLUSH;
}
md_write_start(mddev, bi);
/*
* If array is degraded, better not do chunk aligned read because
* later we might have to read it again in order to reconstruct
@ -5615,6 +5613,7 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
last_sector = bio_end_sector(bi);
bi->bi_next = NULL;
bi->bi_phys_segments = 1; /* over-loaded to count active stripes */
md_write_start(mddev, bi);
prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
@ -5749,11 +5748,11 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
}
finish_wait(&conf->wait_for_overlap, &w);
if (rw == WRITE)
md_write_end(mddev);
remaining = raid5_dec_bi_active_stripes(bi);
if (remaining == 0) {
if ( rw == WRITE )
md_write_end(mddev);
trace_block_bio_complete(bdev_get_queue(bi->bi_bdev),
bi, 0);