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Commit 387bb173 authored by Neil Brown's avatar Neil Brown Committed by Linus Torvalds
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[PATCH] md: fix various bugs with aligned reads in RAID5 



It is possible for raid5 to be sent a bio that is too big for an underlying
device.  So if it is a READ that we pass stright down to a device, it will
fail and confuse RAID5.

So in 'chunk_aligned_read' we check that the bio fits within the parameters
for the target device and if it doesn't fit, fall back on reading through
the stripe cache and making lots of one-page requests.

Note that this is the earliest time we can check against the device because
earlier we don't have a lock on the device, so it could change underneath
us.

Also, the code for handling a retry through the cache when a read fails has
not been tested and was badly broken.  This patch fixes that code.

Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Cc: "Kai" <epimetreus@fastmail.fm>
Cc: <stable@suse.de>
Cc: <org@suse.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6649a386

block/ll_rw_blk.c

+1 −1
Original line number Diff line number Diff line
@@ -1264,7 +1264,7 @@ void blk_recount_segments(request_queue_t *q, struct bio *bio) 
	bio->bi_hw_segments = nr_hw_segs;

	bio->bi_flags |= (1 << BIO_SEG_VALID);

}



EXPORT_SYMBOL(blk_recount_segments);



static int blk_phys_contig_segment(request_queue_t *q, struct bio *bio,

				   struct bio *nxt)

drivers/md/raid5.c

+39 −3
Original line number Diff line number Diff line
@@ -2620,7 +2620,7 @@ static struct bio *remove_bio_from_retry(raid5_conf_t *conf) 
	}

	bi = conf->retry_read_aligned_list;

	if(bi) {

		conf->retry_read_aligned = bi->bi_next;

		conf->retry_read_aligned_list = bi->bi_next;

		bi->bi_next = NULL;

		bi->bi_phys_segments = 1; /* biased count of active stripes */

		bi->bi_hw_segments = 0; /* count of processed stripes */
@@ -2669,6 +2669,27 @@ static int raid5_align_endio(struct bio *bi, unsigned int bytes, int error) 
	return 0;

}



static int bio_fits_rdev(struct bio *bi)

{

	request_queue_t *q = bdev_get_queue(bi->bi_bdev);



	if ((bi->bi_size>>9) > q->max_sectors)

		return 0;

	blk_recount_segments(q, bi);

	if (bi->bi_phys_segments > q->max_phys_segments ||

	    bi->bi_hw_segments > q->max_hw_segments)

		return 0;



	if (q->merge_bvec_fn)

		/* it's too hard to apply the merge_bvec_fn at this stage,

		 * just just give up

		 */

		return 0;



	return 1;

}





static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio)

{

	mddev_t *mddev = q->queuedata;
@@ -2715,6 +2736,13 @@ static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio) 
		align_bi->bi_flags &= ~(1 << BIO_SEG_VALID);

		align_bi->bi_sector += rdev->data_offset;



		if (!bio_fits_rdev(align_bi)) {

			/* too big in some way */

			bio_put(align_bi);

			rdev_dec_pending(rdev, mddev);

			return 0;

		}



		spin_lock_irq(&conf->device_lock);

		wait_event_lock_irq(conf->wait_for_stripe,

				    conf->quiesce == 0,
@@ -3107,7 +3135,9 @@ static int retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio) 
	last_sector = raid_bio->bi_sector + (raid_bio->bi_size>>9);



	for (; logical_sector < last_sector;

	     logical_sector += STRIPE_SECTORS, scnt++) {

	     logical_sector += STRIPE_SECTORS,

		     sector += STRIPE_SECTORS,

		     scnt++) {



		if (scnt < raid_bio->bi_hw_segments)

			/* already done this stripe */
@@ -3123,7 +3153,13 @@ static int retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio) 
		}



		set_bit(R5_ReadError, &sh->dev[dd_idx].flags);

		add_stripe_bio(sh, raid_bio, dd_idx, 0);

		if (!add_stripe_bio(sh, raid_bio, dd_idx, 0)) {

			release_stripe(sh);

			raid_bio->bi_hw_segments = scnt;

			conf->retry_read_aligned = raid_bio;

			return handled;

		}



		handle_stripe(sh, NULL);

		release_stripe(sh);

		handled++;