dm: remove nr_iovecs parameter from alloc_tio() (99778273) · Commits · 戴 / test

alloc_tio() uses bio_alloc_bioset() to allocate a clone-bio for a bio. alloc_tio() takes the number of bvecs to allocate for the clone-bio. However, with v3.14's immutable biovec changes DM now uses __bio_clone_fast() and no longer needs to allocate bvecs. In practice, the 'nr_iovecs' passed to alloc_tio() is always effectively 0. __clone_and_map_simple_bio() looked like it was passing non-zero nr_iovecs, but its value was always within the range of inline bvecs and no allocation actually happened. If allocation happened, the BUG_ON() in __bio_clone_fast() would've triggered. Remove the nr_iovecs parameter from alloc_tio() to prevent possible future bio_alloc_bioset() mis-use of a new bioset interface that will no longer allow bvecs to be allocated. Also fix extra whitespace before the __bio_clone_fast() call in __clone_and_map_simple_bio(). Signed-off-by:

Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Signed-off-by:

Mike Snitzer <snitzer@redhat.com>

drivers/md/dm.c

+5 −10

Original line number	Diff line number	Diff line
		@@ -1249,13 +1249,13 @@ static void clone_bio(struct dm_target_io tio, struct bio bio,
		}

		static struct dm_target_io alloc_tio(struct clone_info ci,
		struct dm_target *ti, int nr_iovecs,
		struct dm_target *ti,
		unsigned target_bio_nr)
		{
		struct dm_target_io *tio;
		struct bio *clone;

		clone = bio_alloc_bioset(GFP_NOIO, nr_iovecs, ci->md->bs);
		clone = bio_alloc_bioset(GFP_NOIO, 0, ci->md->bs);
		tio = container_of(clone, struct dm_target_io, clone);

		tio->io = ci->io;
		@@ -1269,16 +1269,11 @@ static void __clone_and_map_simple_bio(struct clone_info *ci,
		struct dm_target *ti,
		unsigned target_bio_nr, unsigned *len)
		{
		struct dm_target_io *tio = alloc_tio(ci, ti, ci->bio->bi_max_vecs, target_bio_nr);
		struct dm_target_io *tio = alloc_tio(ci, ti, target_bio_nr);
		struct bio *clone = &tio->clone;

		tio->len_ptr = len;

		/*
		* Discard requests require the bio's inline iovecs be initialized.
		* ci->bio->bi_max_vecs is BIO_INLINE_VECS anyway, for both flush
		* and discard, so no need for concern about wasted bvec allocations.
		*/
		__bio_clone_fast(clone, ci->bio);
		if (len)
		bio_setup_sector(clone, ci->sector, *len);
		@@ -1322,7 +1317,7 @@ static void __clone_and_map_data_bio(struct clone_info ci, struct dm_target ti
		num_target_bios = ti->num_write_bios(ti, bio);

		for (target_bio_nr = 0; target_bio_nr < num_target_bios; target_bio_nr++) {
		tio = alloc_tio(ci, ti, 0, target_bio_nr);
		tio = alloc_tio(ci, ti, target_bio_nr);
		tio->len_ptr = len;
		clone_bio(tio, bio, sector, *len);
		__map_bio(tio);

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