Re: [PATCH 2/2] md: raid1: use bio_rewind() before bio_copy_data()
From: NeilBrown <hidden>
Date: 2013-07-09 04:33:52
On Mon, 8 Jul 2013 16:25:14 -0400 Joe Lawrence [off-list ref] wrote:
bio_copy_data() cannot execute on a fully completed source (or destination) bio. MD RAID1 is recycling a completed read bio for RAID repair purposes and needs to fix up the source and destination bios for bio_copy_data(): in particular, the io-vector index needs to be rewound and the bios unchained. Suggested-by: NeilBrown <redacted> Signed-off-by: Joe Lawrence <redacted>
Thanks Joe. Jens: are you happy with this? If so is it OK for me to forward to Linus and -stable for 3.10, or would you rather? The follow-on patch which uses the so avoid a crash is http://marc.info/?l=linux-raid&m=137331514131503&w=2 (This is sitting near the top of "git://neil.brown.name/md for-next" if you want to cherry-pick it). Thanks, NeilBrown
quoted hunk ↗ jump to hunk
--- drivers/md/raid1.c | 28 +++++----------------------- 1 file changed, 5 insertions(+), 23 deletions(-)diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 6e17f81..bb1e80f 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c@@ -1861,7 +1861,6 @@ static int process_checks(struct r1bio *r1_bio) int j; struct bio *pbio = r1_bio->bios[primary]; struct bio *sbio = r1_bio->bios[i]; - int size; if (sbio->bi_end_io != end_sync_read) continue;@@ -1887,28 +1886,11 @@ static int process_checks(struct r1bio *r1_bio) rdev_dec_pending(conf->mirrors[i].rdev, mddev); continue; } - /* fixup the bio for reuse */ - bio_reset(sbio); - sbio->bi_vcnt = vcnt; - sbio->bi_size = r1_bio->sectors << 9; - sbio->bi_sector = r1_bio->sector + - conf->mirrors[i].rdev->data_offset; - sbio->bi_bdev = conf->mirrors[i].rdev->bdev; - sbio->bi_end_io = end_sync_read; - sbio->bi_private = r1_bio; - - size = sbio->bi_size; - for (j = 0; j < vcnt ; j++) { - struct bio_vec *bi; - bi = &sbio->bi_io_vec[j]; - bi->bv_offset = 0; - if (size > PAGE_SIZE) - bi->bv_len = PAGE_SIZE; - else - bi->bv_len = size; - size -= PAGE_SIZE; - } - + /* copy pbio io_vec data into sbio, but first reset io_vec + * index and unchain both */ + bio_rewind(pbio); + bio_rewind(sbio); + pbio->bi_next = sbio->bi_next = NULL; bio_copy_data(sbio, pbio); } return 0;
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