[PATCH] dm.c - device-mapper I/O path fixes

Kevin Corry (corryk@us.ibm.com)
Tue, 10 Dec 2002 16:03:47 -0600


Joe, Linus,

This patch fixes problems with the device-mapper I/O path in 2.5.51. The
existing code does not properly split requests when necessary, and can
cause segfaults and/or data corruption. This can easily manifest itself
when running XFS on striped LVM volumes.

Notes:
- New bio's must be alloc'd instead of clone'd, since the bio vector may need
to be adjusted if the end of the split request does not fill a page.
- Fix reference counting of md->pending. This should only be incremented once
for each incoming bio, not for each split bio that is resubmitted.
- Copy the correct bvec when splitting the tail-end of a page.

-- 
Kevin Corry
corryk@us.ibm.com
http://evms.sourceforge.net/

--- linux-2.5.51a/drivers/md/dm.c Tue Dec 10 11:01:13 2002 +++ linux-2.5.51b/drivers/md/dm.c Tue Dec 10 11:03:55 2002 @@ -242,17 +242,18 @@ static spinlock_t _uptodate_lock = SPIN_LOCK_UNLOCKED; unsigned long flags; - spin_lock_irqsave(&_uptodate_lock, flags); - if (error) + if (error) { + spin_lock_irqsave(&_uptodate_lock, flags); io->error = error; - spin_unlock_irqrestore(&_uptodate_lock, flags); + spin_unlock_irqrestore(&_uptodate_lock, flags); + } if (atomic_dec_and_test(&io->io_count)) { if (atomic_dec_and_test(&io->md->pending)) /* nudge anyone waiting on suspend queue */ wake_up(&io->md->wait); - bio_endio(io->bio, io->error ? 0 : io->bio->bi_size, io->error); + bio_endio(io->bio, io->bio->bi_size, io->error); free_io(io); } } @@ -261,15 +262,15 @@ { struct dm_io *io = bio->bi_private; - /* - * Only call dec_pending if the clone has completely - * finished. If a partial io errors I'm assuming it won't - * be requeued. FIXME: check this. - */ - if (error || !bio->bi_size) { - dec_pending(io, error); - bio_put(bio); + if (bio->bi_size) + return 1; + + if (error) { + struct gendisk *disk = dm_disk(io->md); + DMWARN("I/O error (%d) on device %s\n", error, disk->disk_name); } + dec_pending(io, error); + bio_put(bio); return 0; } @@ -313,7 +314,6 @@ * anything, the target has assumed ownership of * this io. */ - atomic_inc(&io->md->pending); atomic_inc(&io->io_count); r = ti->type->map(ti, clone); if (r > 0) @@ -341,9 +341,7 @@ { struct dm_target *ti = dm_table_find_target(ci->md->map, ci->sector); struct bio *clone, *bio = ci->bio; - struct bio_vec *bv = bio->bi_io_vec + (bio->bi_vcnt - 1); - - DMWARN("splitting page"); + struct bio_vec *bv = bio->bi_io_vec + ci->idx; if (len > ci->sector_count) len = ci->sector_count; @@ -353,11 +351,13 @@ clone->bi_sector = ci->sector; clone->bi_bdev = bio->bi_bdev; - clone->bi_flags = bio->bi_flags | (1 << BIO_SEG_VALID); clone->bi_rw = bio->bi_rw; + clone->bi_vcnt = 1; clone->bi_size = len << SECTOR_SHIFT; clone->bi_end_io = clone_endio; clone->bi_private = ci->io; + clone->bi_io_vec->bv_offset = clone->bi_io_vec->bv_len - clone->bi_size; + clone->bi_io_vec->bv_len = clone->bi_size; ci->sector += len; ci->sector_count -= len; @@ -369,24 +369,48 @@ { struct bio *clone, *bio = ci->bio; struct dm_target *ti = dm_table_find_target(ci->md->map, ci->sector); - sector_t len = max_io_len(ci->md, bio->bi_sector, ti); + sector_t bv_len, len = max_io_len(ci->md, ci->sector, ti); + struct bio_vec *bv; + int i, vcnt = bio->bi_vcnt - ci->idx; /* shorter than current target ? */ if (ci->sector_count < len) len = ci->sector_count; /* create the clone */ - clone = bio_clone(ci->bio, GFP_NOIO); + clone = bio_alloc(GFP_NOIO, vcnt); + if (!clone) { + dec_pending(ci->io, -ENOMEM); + return; + } clone->bi_sector = ci->sector; - clone->bi_idx = ci->idx; + clone->bi_bdev = bio->bi_bdev; + clone->bi_rw = bio->bi_rw; + clone->bi_vcnt = vcnt; clone->bi_size = len << SECTOR_SHIFT; clone->bi_end_io = clone_endio; clone->bi_private = ci->io; + /* copy the original vector and adjust if necessary. */ + memcpy(clone->bi_io_vec, bio->bi_io_vec + ci->idx, + vcnt * sizeof(*clone->bi_io_vec)); + bv_len = len << SECTOR_SHIFT; + bio_for_each_segment(bv, clone, i) { + if (bv_len >= bv->bv_len) { + bv_len -= bv->bv_len; + } else { + bv->bv_len = bv_len; + clone->bi_vcnt = i + 1; + break; + } + } + + /* submit this io */ + __map_bio(ti, clone); + /* adjust the remaining io */ ci->sector += len; ci->sector_count -= len; - __map_bio(ti, clone); /* * If we are not performing all remaining io in this @@ -395,8 +419,8 @@ */ if (ci->sector_count) { while (len) { - struct bio_vec *bv = clone->bi_io_vec + ci->idx; - sector_t bv_len = bv->bv_len >> SECTOR_SHIFT; + bv = bio->bi_io_vec + ci->idx; + bv_len = bv->bv_len >> SECTOR_SHIFT; if (bv_len <= len) len -= bv_len; @@ -427,6 +451,8 @@ ci.sector_count = bio_sectors(bio); ci.idx = 0; + atomic_inc(&ci.io->md->pending); + while (ci.sector_count) __clone_and_map(&ci); @@ -457,13 +483,13 @@ up_read(&md->lock); if (bio_rw(bio) == READA) { - bio_io_error(bio, 0); + bio_io_error(bio, bio->bi_size); return 0; } r = queue_io(md, bio); if (r < 0) { - bio_io_error(bio, 0); + bio_io_error(bio, bio->bi_size); return 0; } else if (r == 0) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/