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md: incorporate new plugging into raid5. 

In raid5 plugging is used for 2 things:
 1/ collecting writes that require a bitmap update
 2/ collecting writes in the hope that we can create full
    stripes - or at least more-full.

We now release these different sets of stripes when plug_cnt
is zero.

Also in make_request, we call mddev_check_plug to hopefully increase
plug_cnt, and wake up the thread at the end if plugging wasn't
achieved for some reason.

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2011-04-18 18:25:43 +10:00
parent 97658cdd3a
commit 7c13edc875
1 changed files with 16 additions and 7 deletions
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23
drivers/md/raid5.c
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@ -27,12 +27,12 @@
*
* We group bitmap updates into batches. Each batch has a number.
* We may write out several batches at once, but that isn't very important.
* conf->bm_write is the number of the last batch successfully written.
* conf->bm_flush is the number of the last batch that was closed to
* conf->seq_write is the number of the last batch successfully written.
* conf->seq_flush is the number of the last batch that was closed to
* new additions.
* When we discover that we will need to write to any block in a stripe
* (in add_stripe_bio) we update the in-memory bitmap and record in sh->bm_seq
* the number of the batch it will be in. This is bm_flush+1.
* the number of the batch it will be in. This is seq_flush+1.
* When we are ready to do a write, if that batch hasn't been written yet,
* we plug the array and queue the stripe for later.
* When an unplug happens, we increment bm_flush, thus closing the current
@ -459,7 +459,7 @@ get_active_stripe(raid5_conf_t *conf, sector_t sector,
< (conf->max_nr_stripes *3/4)
|| !conf->inactive_blocked),
conf->device_lock,
md_wakeup_thread(conf->mddev->thread));
);
conf->inactive_blocked = 0;
} else
init_stripe(sh, sector, previous);
@ -3927,6 +3927,7 @@ static int make_request(mddev_t *mddev, struct bio * bi)
struct stripe_head *sh;
const int rw = bio_data_dir(bi);
int remaining;
int plugged;
if (unlikely(bi->bi_rw & REQ_FLUSH)) {
md_flush_request(mddev, bi);
@ -3945,6 +3946,7 @@ static int make_request(mddev_t *mddev, struct bio * bi)
bi->bi_next = NULL;
bi->bi_phys_segments = 1; /* over-loaded to count active stripes */
plugged = mddev_check_plugged(mddev);
for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
DEFINE_WAIT(w);
int disks, data_disks;
@ -4059,6 +4061,9 @@ static int make_request(mddev_t *mddev, struct bio * bi)
}
}
if (!plugged)
md_wakeup_thread(mddev->thread);
spin_lock_irq(&conf->device_lock);
remaining = raid5_dec_bi_phys_segments(bi);
spin_unlock_irq(&conf->device_lock);
@ -4472,14 +4477,18 @@ static void raid5d(mddev_t *mddev)
while (1) {
struct bio *bio;
if (conf->seq_flush != conf->seq_write) {
int seq = conf->seq_flush;
if (atomic_read(&mddev->plug_cnt) == 0 &&
!list_empty(&conf->bitmap_list)) {
/* Now is a good time to flush some bitmap updates */
conf->seq_flush++;
spin_unlock_irq(&conf->device_lock);
bitmap_unplug(mddev->bitmap);
spin_lock_irq(&conf->device_lock);
conf->seq_write = seq;
conf->seq_write = conf->seq_flush;
activate_bit_delay(conf);
}
if (atomic_read(&mddev->plug_cnt) == 0)
raid5_activate_delayed(conf);
while ((bio = remove_bio_from_retry(conf))) {
int ok;