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[PATCH] md: fix various bugs with aligned reads in RAID5

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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: Neil 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Neil Brown 2007-02-08 14:20:29 -08:00 committed by Linus Torvalds
parent 6649a38632
commit 387bb17374
2 changed files with 40 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
block/ll_rw_blk.c
View file

@ -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)

42
drivers/md/raid5.c
View file

@ -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++;