Commit 016c76ac authored by NeilBrown's avatar NeilBrown Committed by Shaohua Li
Browse files

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



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: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
parent bd83d0a2

drivers/md/raid5-cache.c

+1 −2
Original line number Diff line number Diff line
@@ -318,7 +318,6 @@ 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);

		wbi = wbi2;

	}

drivers/md/raid5.c

+13 −44
Original line number Diff line number Diff line
@@ -1322,7 +1322,6 @@ 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);

				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) {
@@ -3384,7 +3375,6 @@ 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);

			bi = nextbi;

		}
@@ -3407,7 +3397,6 @@ 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);

			bi = bi2;

		}
@@ -3433,7 +3422,6 @@ 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);

				bi = nextbi;

			}
@@ -3766,7 +3754,6 @@ 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);

					wbi = wbi2;

				}
@@ -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++;

		}
@@ -5532,11 +5517,8 @@ 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);

}

}



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);
@@ -5726,15 +5706,8 @@ 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);

}

}



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);

	}



	if (atomic_dec_and_test(&conf->active_aligned_reads))

		wake_up(&conf->wait_for_quiescent);

	return handled;

drivers/md/raid5.h

+1 −16
Original line number Diff line number Diff line
@@ -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)

{

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