dm crypt: use smaller bvecs in clones

Allocate smaller clones

With the previous dm-crypt fixes, there is no need for the clone bios to have
the same bvec size as the original - we just need to make them big enough for
the remaining number of pages.  The only requirement is that we clear the
"out" index in convert_context, so that crypt_convert starts storing data at
the right position within the clone bio.

Signed-off-by: Olaf Kirch <olaf.kirch@oracle.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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>

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 339b575..1ecee5e 100644 (file)
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -379,8 +379,7 @@ static int crypt_convert(struct crypt_config *cc,
  * This should never violate the device limitations
  * May return a smaller bio when running out of pages
  */
-static struct bio *crypt_alloc_buffer(struct crypt_io *io, unsigned int size,
-                                     unsigned int *bio_vec_idx)
+static struct bio *crypt_alloc_buffer(struct crypt_io *io, unsigned int size)
 {
        struct crypt_config *cc = io->target->private;
        struct bio *clone;
@@ -394,16 +393,7 @@ static struct bio *crypt_alloc_buffer(struct crypt_io *io, unsigned int size,
 
        clone_init(io, clone);
 
-       /* if the last bio was not complete, continue where that one ended */
-       clone->bi_idx = *bio_vec_idx;
-       clone->bi_vcnt = *bio_vec_idx;
-       clone->bi_size = 0;
-       clone->bi_flags &= ~(1 << BIO_SEG_VALID);
-
-       /* clone->bi_idx pages have already been allocated */
-       size -= clone->bi_idx * PAGE_SIZE;
-
-       for (i = clone->bi_idx; i < nr_iovecs; i++) {
+       for (i = 0; i < nr_iovecs; i++) {
                struct bio_vec *bv = bio_iovec_idx(clone, i);
 
                bv->bv_page = mempool_alloc(cc->page_pool, gfp_mask);
@@ -415,7 +405,7 @@ static struct bio *crypt_alloc_buffer(struct crypt_io *io, unsigned int size,
                 * return a partially allocated bio, the caller will then try
                 * to allocate additional bios while submitting this partial bio
                 */
-               if ((i - clone->bi_idx) == (MIN_BIO_PAGES - 1))
+               if (i == (MIN_BIO_PAGES - 1))
                        gfp_mask = (gfp_mask | __GFP_NOWARN) & ~__GFP_WAIT;
 
                bv->bv_offset = 0;
@@ -434,12 +424,6 @@ static struct bio *crypt_alloc_buffer(struct crypt_io *io, unsigned int size,
                return NULL;
        }
 
-       /*
-        * Remember the last bio_vec allocated to be able
-        * to correctly continue after the splitting.
-        */
-       *bio_vec_idx = clone->bi_vcnt;
-
        return clone;
 }
 
@@ -597,7 +581,6 @@ static void process_write(struct crypt_io *io)
        struct convert_context ctx;
        unsigned remaining = base_bio->bi_size;
        sector_t sector = base_bio->bi_sector - io->target->begin;
-       unsigned bvec_idx = 0;
 
        atomic_inc(&io->pending);
 
@@ -608,13 +591,14 @@ static void process_write(struct crypt_io *io)
         * so repeat the whole process until all the data can be handled.
         */
        while (remaining) {
-               clone = crypt_alloc_buffer(io, base_bio->bi_size, &bvec_idx);
+               clone = crypt_alloc_buffer(io, remaining);
                if (unlikely(!clone)) {
                        dec_pending(io, -ENOMEM);
                        return;
                }
 
                ctx.bio_out = clone;
+               ctx.idx_out = 0;
 
                if (unlikely(crypt_convert(cc, &ctx) < 0)) {
                        crypt_free_buffer_pages(cc, clone, clone->bi_size);
@@ -623,6 +607,9 @@ static void process_write(struct crypt_io *io)
                        return;
                }
 
+               /* crypt_convert should have filled the clone bio */
+               BUG_ON(ctx.idx_out < clone->bi_vcnt);
+
                clone->bi_sector = cc->start + sector;
                remaining -= clone->bi_size;
                sector += bio_sectors(clone);