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md/raid5: use bio_inc_remaining() instead of repurposing bi_phys_segments as a counter

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md/raid5 needs to keep track of how many stripe_heads are processing a
bio so that it can delay calling bio_endio() until all stripe_heads
have completed.  It currently uses 16 bits of ->bi_phys_segments for
this purpose.

16 bits is only enough for 256M requests, and it is possible for a
single bio to be larger than this, which causes problems.  Also, the
bio struct contains a larger counter, __bi_remaining, which has a
purpose very similar to the purpose of our counter.  So stop using
->bi_phys_segments, and instead use __bi_remaining.

This means we don't need to initialize the counter, as our caller
initializes it to '1'.  It also means we can call bio_endio() directly
as it tests this counter internally.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
This commit is contained in:
NeilBrown 2017-03-15 14:05:13 +11:00 committed by Shaohua Li
parent bd83d0a28c
commit 016c76ac76
3 changed files with 15 additions and 62 deletions
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3
drivers/md/raid5-cache.c
View File

@ -318,8 +318,7 @@ r5c_return_dev_pending_writes(struct r5conf *conf, struct r5dev *dev)
dev->sector + STRIPE_SECTORS) {
wbi2 = r5_next_bio(wbi, dev->sector);
md_write_end(conf->mddev);
if (!raid5_dec_bi_active_stripes(wbi))
bio_endio(wbi);
bio_endio(wbi);
wbi = wbi2;
}
}

57
drivers/md/raid5.c
View File

@ -1322,8 +1322,7 @@ static void ops_complete_biofill(void *stripe_head_ref)
while (rbi && rbi->bi_iter.bi_sector <
dev->sector + STRIPE_SECTORS) {
rbi2 = r5_next_bio(rbi, dev->sector);
if (!raid5_dec_bi_active_stripes(rbi))
bio_endio(rbi);
bio_endio(rbi);
rbi = rbi2;
}
}
@ -3196,14 +3195,6 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
(unsigned long long)bi->bi_iter.bi_sector,
(unsigned long long)sh->sector);
/*
* If several bio share a stripe. The bio bi_phys_segments acts as a
* reference count to avoid race. The reference count should already be
* increased before this function is called (for example, in
* raid5_make_request()), so other bio sharing this stripe will not free the
* stripe. If a stripe is owned by one stripe, the stripe lock will
* protect it.
*/
spin_lock_irq(&sh->stripe_lock);
/* Don't allow new IO added to stripes in batch list */
if (sh->batch_head)
@ -3259,7 +3250,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
if (*bip)
bi->bi_next = *bip;
*bip = bi;
raid5_inc_bi_active_stripes(bi);
bio_inc_remaining(bi);
md_write_inc(conf->mddev, bi);
if (forwrite) {
@ -3384,8 +3375,7 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
bi->bi_error = -EIO;
md_write_end(conf->mddev);
if (!raid5_dec_bi_active_stripes(bi))
bio_endio(bi);
bio_endio(bi);
bi = nextbi;
}
if (bitmap_end)
@ -3407,8 +3397,7 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
bi->bi_error = -EIO;
md_write_end(conf->mddev);
if (!raid5_dec_bi_active_stripes(bi))
bio_endio(bi);
bio_endio(bi);
bi = bi2;
}
@ -3433,8 +3422,7 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
r5_next_bio(bi, sh->dev[i].sector);
bi->bi_error = -EIO;
if (!raid5_dec_bi_active_stripes(bi))
bio_endio(bi);
bio_endio(bi);
bi = nextbi;
}
}
@ -3766,8 +3754,7 @@ returnbi:
dev->sector + STRIPE_SECTORS) {
wbi2 = r5_next_bio(wbi, dev->sector);
md_write_end(conf->mddev);
if (!raid5_dec_bi_active_stripes(wbi))
bio_endio(wbi);
bio_endio(wbi);
wbi = wbi2;
}
bitmap_endwrite(conf->mddev->bitmap, sh->sector,
@ -5112,7 +5099,7 @@ static struct bio *remove_bio_from_retry(struct r5conf *conf)
* this sets the active strip count to 1 and the processed
* strip count to zero (upper 8 bits)
*/
raid5_set_bi_stripes(bi, 1); /* biased count of active stripes */
raid5_set_bi_processed_stripes(bi, 0);
}
return bi;
@ -5449,7 +5436,6 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
struct r5conf *conf = mddev->private;
sector_t logical_sector, last_sector;
struct stripe_head *sh;
int remaining;
int stripe_sectors;
if (mddev->reshape_position != MaxSector)
@ -5460,7 +5446,6 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
last_sector = bi->bi_iter.bi_sector + (bi->bi_iter.bi_size>>9);
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 *
@ -5507,7 +5492,7 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
continue;
sh->dev[d].towrite = bi;
set_bit(R5_OVERWRITE, &sh->dev[d].flags);
raid5_inc_bi_active_stripes(bi);
bio_inc_remaining(bi);
md_write_inc(mddev, bi);
sh->overwrite_disks++;
}
@ -5532,10 +5517,7 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
}
md_write_end(mddev);
remaining = raid5_dec_bi_active_stripes(bi);
if (remaining == 0) {
bio_endio(bi);
}
bio_endio(bi);
}
static void raid5_make_request(struct mddev *mddev, struct bio * bi)
@ -5546,7 +5528,6 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
sector_t logical_sector, last_sector;
struct stripe_head *sh;
const int rw = bio_data_dir(bi);
int remaining;
DEFINE_WAIT(w);
bool do_prepare;
bool do_flush = false;
@ -5588,7 +5569,6 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
logical_sector = bi->bi_iter.bi_sector & ~((sector_t)STRIPE_SECTORS-1);
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);
@ -5726,14 +5706,7 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
if (rw == WRITE)
md_write_end(mddev);
remaining = raid5_dec_bi_active_stripes(bi);
if (remaining == 0) {
trace_block_bio_complete(bdev_get_queue(bi->bi_bdev),
bi, 0);
bio_endio(bi);
}
bio_endio(bi);
}
static sector_t raid5_size(struct mddev *mddev, sector_t sectors, int raid_disks);
@ -6098,7 +6071,6 @@ static int retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
int dd_idx;
sector_t sector, logical_sector, last_sector;
int scnt = 0;
int remaining;
int handled = 0;
logical_sector = raid_bio->bi_iter.bi_sector &
@ -6137,12 +6109,9 @@ static int retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
raid5_release_stripe(sh);
handled++;
}
remaining = raid5_dec_bi_active_stripes(raid_bio);
if (remaining == 0) {
trace_block_bio_complete(bdev_get_queue(raid_bio->bi_bdev),
raid_bio, 0);
bio_endio(raid_bio);
}
bio_endio(raid_bio);
if (atomic_dec_and_test(&conf->active_aligned_reads))
wake_up(&conf->wait_for_quiescent);
return handled;

17
drivers/md/raid5.h
View File

@ -488,8 +488,7 @@ static inline struct bio *r5_next_bio(struct bio *bio, sector_t sector)
}
/*
* We maintain a biased count of active stripes in the bottom 16 bits of
* bi_phys_segments, and a count of processed stripes in the upper 16 bits
* We maintain a count of processed stripes in the upper 16 bits
*/
static inline int raid5_bi_processed_stripes(struct bio *bio)
{
@ -498,20 +497,6 @@ static inline int raid5_bi_processed_stripes(struct bio *bio)
return (atomic_read(segments) >> 16) & 0xffff;
}
static inline int raid5_dec_bi_active_stripes(struct bio *bio)
{
atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
return atomic_sub_return(1, segments) & 0xffff;
}
static inline void raid5_inc_bi_active_stripes(struct bio *bio)
{
atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
atomic_inc(segments);
}
static inline void raid5_set_bi_processed_stripes(struct bio *bio,
unsigned int cnt)
{