On Tue, 30 Aug 2016, Mike Snitzer wrote: > On Tue, Aug 30 2016 at 8:19P -0400, > Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > > > > > On Tue, 30 Aug 2016, Ming Lei wrote: > > > > > On Tue, Aug 30, 2016 at 5:57 AM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > > > > > > > > > > On Mon, 29 Aug 2016, Ming Lei wrote: > > > > > > > >> On Sat, Aug 27, 2016 at 11:09 PM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > >> > > > > >> > But this patch won't work for device mapper, blk_bio_segment_split is > > > >> > called from blk_queue_split and device mapper doesn't use blk_queue_split > > > >> > (it can't because it frees queue->bio_split). > > > >> > > > > >> > We still need these two patches: > > > >> > https://www.redhat.com/archives/dm-devel/2016-May/msg00211.html > > > >> > https://www.redhat.com/archives/dm-devel/2016-May/msg00210.html > > > >> > > > >> About the 2nd patch, it might not be good enough because in theory > > > >> a small size bio still may include big bvecs, such as, each bvec points > > > >> to 512byte buffer, so strictly speaking the bvec number should > > > >> be checked instead of bio size. > > > >> > > > >> Ming Lei > > > > > > > > This is not a problem. > > > > > > I meant the following code in your 2nd patch: > > > > > > + if (unlikely(bio->bi_iter.bi_size > BIO_MAX_SIZE) && > > > + (bio->bi_rw & (REQ_FLUSH | REQ_DISCARD | REQ_WRITE)) == REQ_WRITE) > > > + dm_accept_partial_bio(bio, BIO_MAX_SIZE >> SECTOR_SHIFT); > > > > > > And the check on .bi_size may not work. > > > > kcryptd_crypt_write_convert calls: > > crypt_alloc_buffer(io, io->base_bio->bi_iter.bi_size) > > > > crypt_alloc_buffer does: > > unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; > > clone = bio_alloc_bioset(GFP_NOIO, nr_iovecs, cc->bs); > > > > So, if io->base_bio->bi_iter.bi_size <= BIO_MAX_SIZE, then nr_iovecs will > > be less or equal than BIO_MAX_PAGES and the function bio_alloc_bioset will > > succeed. > > > > (BTW. BIO_MAX_SIZE was removed in the current kernel, we should use > > (BIO_MAX_PAGES << PAGE_SHIFT) instead). > > Is this revised patch OK with you? Drop that "#ifdef CONFIG_BCACHE". Anyone should be allowed to create a big bio, not just bcache. That one test has no performance impact, there is no need to hide it behind #ifdef. Mikulas > From: Mikulas Patocka <mpatocka@xxxxxxxxxx> > Date: Tue, 30 Aug 2016 16:38:42 -0400 > Subject: [PATCH] dm crypt: fix error with too large bcache bios > > When dm-crypt processes writes, it allocates a new bio in > crypt_alloc_buffer(). The bio is allocated from a bio set and it can > have at most BIO_MAX_PAGES vector entries, however the incoming bio can be > larger if it was allocated by bcache. If the incoming bio is larger, > bio_alloc_bioset() fails and an error is returned. > > To avoid the error, we test for a too large bio in the function > crypt_map() and use dm_accept_partial_bio() to split the bio. > dm_accept_partial_bio() trims the current bio to the desired size and > asks DM core to send another bio with the rest of the data. > > This fix is wrapped with a check for CONFIG_BCACHE because there > currently isn't any other code that generates too large bios. So unless > bcache is configured there is no point wasting time making this check. > > Signed-off-by: Mikulas Patocka <mpatocka redhat com> > Cc: stable@xxxxxxxxxxxxxxx # v3.16+ > --- > drivers/md/dm-crypt.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c > index eedba67..743f548 100644 > --- a/drivers/md/dm-crypt.c > +++ b/drivers/md/dm-crypt.c > @@ -1924,6 +1924,12 @@ static int crypt_map(struct dm_target *ti, struct bio *bio) > return DM_MAPIO_REMAPPED; > } > > +#ifdef CONFIG_BCACHE > + if (unlikely(bio->bi_iter.bi_size > (BIO_MAX_PAGES << PAGE_SHIFT)) && > + bio_data_dir(bio) == WRITE) > + dm_accept_partial_bio(bio, ((BIO_MAX_PAGES << PAGE_SHIFT) >> SECTOR_SHIFT)); > +#endif > + > io = dm_per_bio_data(bio, cc->per_bio_data_size); > crypt_io_init(io, cc, bio, dm_target_offset(ti, bio->bi_iter.bi_sector)); > io->ctx.req = (struct skcipher_request *)(io + 1); > -- > 2.7.4 (Apple Git-66) > -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
