block: introduce struct rq_map_data to use reserved pages

This patch introduces struct rq_map_data to enable bio_copy_use_iov()
use reserved pages.

Currently, bio_copy_user_iov allocates bounce pages but
drivers/scsi/sg.c wants to allocate pages by itself and use
them. struct rq_map_data can be used to pass allocated pages to
bio_copy_user_iov.

The current users of bio_copy_user_iov simply passes NULL (they don't
want to use pre-allocated pages).

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Douglas Gilbert <dougg@torque.net>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 41 insertions, 17 deletions

diff --git a/fs/bio.c b/fs/bio.c
index 3d2e9ad24728..a2f072647cdf 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -439,16 +439,19 @@ int bio_add_page(struct bio *bio, struct page *page, unsigned int len,
 
 struct bio_map_data {
         struct bio_vec *iovecs;
-        int nr_sgvecs;
         struct sg_iovec *sgvecs;
+        int nr_sgvecs;
+        int is_our_pages;
 };
 
 static void bio_set_map_data(struct bio_map_data *bmd, struct bio *bio,
-                             struct sg_iovec *iov, int iov_count)
+                             struct sg_iovec *iov, int iov_count,
+                             int is_our_pages)
 {
         memcpy(bmd->iovecs, bio->bi_io_vec, sizeof(struct bio_vec) * bio->bi_vcnt);
         memcpy(bmd->sgvecs, iov, sizeof(struct sg_iovec) * iov_count);
         bmd->nr_sgvecs = iov_count;
+        bmd->is_our_pages = is_our_pages;
         bio->bi_private = bmd;
 }
 
@@ -483,7 +486,8 @@ static struct bio_map_data *bio_alloc_map_data(int nr_segs, int iov_count,
 }
 
 static int __bio_copy_iov(struct bio *bio, struct bio_vec *iovecs,
-                          struct sg_iovec *iov, int iov_count, int uncopy)
+                          struct sg_iovec *iov, int iov_count, int uncopy,
+                          int do_free_page)
 {
         int ret = 0, i;
         struct bio_vec *bvec;
@@ -526,7 +530,7 @@ static int __bio_copy_iov(struct bio *bio, struct bio_vec *iovecs,
                         }
                 }
 
-                if (uncopy)
+                if (do_free_page)
                         __free_page(bvec->bv_page);
         }
 
@@ -545,7 +549,8 @@ int bio_uncopy_user(struct bio *bio)
         struct bio_map_data *bmd = bio->bi_private;
         int ret;
 
-        ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs, bmd->nr_sgvecs, 1);
+        ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs, bmd->nr_sgvecs, 1,
+                             bmd->is_our_pages);
 
         bio_free_map_data(bmd);
         bio_put(bio);
@@ -555,6 +560,7 @@ int bio_uncopy_user(struct bio *bio)
 /**
  *      bio_copy_user_iov       -       copy user data to bio
  *      @q: destination block queue
+ *      @map_data: pointer to the rq_map_data holding pages (if necessary)
  *      @iov:   the iovec.
  *      @iov_count: number of elements in the iovec
  *      @write_to_vm: bool indicating writing to pages or not
@@ -564,8 +570,10 @@ int bio_uncopy_user(struct bio *bio)
  *      to/from kernel pages as necessary. Must be paired with
  *      call bio_uncopy_user() on io completion.
  */
-struct bio *bio_copy_user_iov(struct request_queue *q, struct sg_iovec *iov,
-                              int iov_count, int write_to_vm, gfp_t gfp_mask)
+struct bio *bio_copy_user_iov(struct request_queue *q,
+                              struct rq_map_data *map_data,
+                              struct sg_iovec *iov, int iov_count,
+                              int write_to_vm, gfp_t gfp_mask)
 {
         struct bio_map_data *bmd;
         struct bio_vec *bvec;
@@ -600,13 +608,26 @@ struct bio *bio_copy_user_iov(struct request_queue *q, struct sg_iovec *iov,
         bio->bi_rw |= (!write_to_vm << BIO_RW);
 
         ret = 0;
+        i = 0;
         while (len) {
-                unsigned int bytes = PAGE_SIZE;
+                unsigned int bytes;
+
+                if (map_data)
+                        bytes = 1U << (PAGE_SHIFT + map_data->page_order);
+                else
+                        bytes = PAGE_SIZE;
 
                 if (bytes > len)
                         bytes = len;
 
-                page = alloc_page(q->bounce_gfp | gfp_mask);
+                if (map_data) {
+                        if (i == map_data->nr_entries) {
+                                ret = -ENOMEM;
+                                break;
+                        }
+                        page = map_data->pages[i++];
+                } else
+                        page = alloc_page(q->bounce_gfp | gfp_mask);
                 if (!page) {
                         ret = -ENOMEM;
                         break;
@@ -625,16 +646,17 @@ struct bio *bio_copy_user_iov(struct request_queue *q, struct sg_iovec *iov,
          * success
          */
         if (!write_to_vm) {
-                ret = __bio_copy_iov(bio, bio->bi_io_vec, iov, iov_count, 0);
+                ret = __bio_copy_iov(bio, bio->bi_io_vec, iov, iov_count, 0, 0);
                 if (ret)
                         goto cleanup;
         }
 
-        bio_set_map_data(bmd, bio, iov, iov_count);
+        bio_set_map_data(bmd, bio, iov, iov_count, map_data ? 0 : 1);
         return bio;
 cleanup:
-        bio_for_each_segment(bvec, bio, i)
-                __free_page(bvec->bv_page);
+        if (!map_data)
+                bio_for_each_segment(bvec, bio, i)
+                        __free_page(bvec->bv_page);
 
         bio_put(bio);
 out_bmd:
@@ -645,6 +667,7 @@ out_bmd:
 /**
  *      bio_copy_user   -       copy user data to bio
  *      @q: destination block queue
+ *      @map_data: pointer to the rq_map_data holding pages (if necessary)
  *      @uaddr: start of user address
  *      @len: length in bytes
  *      @write_to_vm: bool indicating writing to pages or not
@@ -654,15 +677,16 @@ out_bmd:
  *      to/from kernel pages as necessary. Must be paired with
  *      call bio_uncopy_user() on io completion.
  */
-struct bio *bio_copy_user(struct request_queue *q, unsigned long uaddr,
-                          unsigned int len, int write_to_vm, gfp_t gfp_mask)
+struct bio *bio_copy_user(struct request_queue *q, struct rq_map_data *map_data,
+                          unsigned long uaddr, unsigned int len,
+                          int write_to_vm, gfp_t gfp_mask)
 {
         struct sg_iovec iov;
 
         iov.iov_base = (void __user *)uaddr;
         iov.iov_len = len;
 
-        return bio_copy_user_iov(q, &iov, 1, write_to_vm, gfp_mask);
+        return bio_copy_user_iov(q, map_data, &iov, 1, write_to_vm, gfp_mask);
 }
 
 static struct bio *__bio_map_user_iov(struct request_queue *q,
@@ -1028,7 +1052,7 @@ struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
         bio->bi_private = bmd;
         bio->bi_end_io = bio_copy_kern_endio;
 
-        bio_set_map_data(bmd, bio, &iov, 1);
+        bio_set_map_data(bmd, bio, &iov, 1, 1);
         return bio;
 cleanup:
         bio_for_each_segment(bvec, bio, i)