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>

1 files changed, 8 insertions, 21 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 339b575ce07f..1ecee5e1c548 100644
--- 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);