bio: fix bio_copy_kern() handling of bio->bv_len

The commit 68154e90c9d1492d570671ae181d9a8f8530da55 introduced
bio_copy_kern() to add bounce support to blk_rq_map_kern.

bio_copy_kern() uses bio->bv_len to copy data for READ commands after
the completion but it doesn't work with a request that partially
completed. SCSI always completes a PC request as a whole but seems
some don't.

This patch fixes bio_copy_kern to handle the above case. As
bio_copy_user does, bio_copy_kern uses struct bio_map_data to store
struct bio_vec.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Reported-by: Nix <nix@esperi.org.uk>
Tested-by: Nix <nix@esperi.org.uk>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 28 insertions, 10 deletions

diff --git a/fs/bio.c b/fs/bio.c
index 8000e2fa16cb..8b1f5ee6f83c 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -469,20 +469,21 @@ static void bio_free_map_data(struct bio_map_data *bmd)
         kfree(bmd);
 }
 
-static struct bio_map_data *bio_alloc_map_data(int nr_segs, int iov_count)
+static struct bio_map_data *bio_alloc_map_data(int nr_segs, int iov_count,
+                                               gfp_t gfp_mask)
 {
-        struct bio_map_data *bmd = kmalloc(sizeof(*bmd), GFP_KERNEL);
+        struct bio_map_data *bmd = kmalloc(sizeof(*bmd), gfp_mask);
 
         if (!bmd)
                 return NULL;
 
-        bmd->iovecs = kmalloc(sizeof(struct bio_vec) * nr_segs, GFP_KERNEL);
+        bmd->iovecs = kmalloc(sizeof(struct bio_vec) * nr_segs, gfp_mask);
         if (!bmd->iovecs) {
                 kfree(bmd);
                 return NULL;
         }
 
-        bmd->sgvecs = kmalloc(sizeof(struct sg_iovec) * iov_count, GFP_KERNEL);
+        bmd->sgvecs = kmalloc(sizeof(struct sg_iovec) * iov_count, gfp_mask);
         if (bmd->sgvecs)
                 return bmd;
 
@@ -596,7 +597,7 @@ struct bio *bio_copy_user_iov(struct request_queue *q, struct sg_iovec *iov,
                 len += iov[i].iov_len;
         }
 
-        bmd = bio_alloc_map_data(nr_pages, iov_count);
+        bmd = bio_alloc_map_data(nr_pages, iov_count, GFP_KERNEL);
         if (!bmd)
                 return ERR_PTR(-ENOMEM);
 
@@ -942,19 +943,22 @@ static void bio_copy_kern_endio(struct bio *bio, int err)
 {
         struct bio_vec *bvec;
         const int read = bio_data_dir(bio) == READ;
-        char *p = bio->bi_private;
+        struct bio_map_data *bmd = bio->bi_private;
         int i;
+        char *p = bmd->sgvecs[0].iov_base;
 
         __bio_for_each_segment(bvec, bio, i, 0) {
                 char *addr = page_address(bvec->bv_page);
+                int len = bmd->iovecs[i].bv_len;
 
                 if (read && !err)
-                        memcpy(p, addr, bvec->bv_len);
+                        memcpy(p, addr, len);
 
                 __free_page(bvec->bv_page);
-                p += bvec->bv_len;
+                p += len;
         }
 
+        bio_free_map_data(bmd);
         bio_put(bio);
 }
 
@@ -978,11 +982,21 @@ struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
         const int nr_pages = end - start;
         struct bio *bio;
         struct bio_vec *bvec;
+        struct bio_map_data *bmd;
         int i, ret;
+        struct sg_iovec iov;
+
+        iov.iov_base = data;
+        iov.iov_len = len;
+
+        bmd = bio_alloc_map_data(nr_pages, 1, gfp_mask);
+        if (!bmd)
+                return ERR_PTR(-ENOMEM);
 
+        ret = -ENOMEM;
         bio = bio_alloc(gfp_mask, nr_pages);
         if (!bio)
-                return ERR_PTR(-ENOMEM);
+                goto out_bmd;
 
         while (len) {
                 struct page *page;
@@ -1016,14 +1030,18 @@ struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
                 }
         }
 
-        bio->bi_private = data;
+        bio->bi_private = bmd;
         bio->bi_end_io = bio_copy_kern_endio;
+
+        bio_set_map_data(bmd, bio, &iov, 1);
         return bio;
 cleanup:
         bio_for_each_segment(bvec, bio, i)
                 __free_page(bvec->bv_page);
 
         bio_put(bio);
+out_bmd:
+        bio_free_map_data(bmd);
 
         return ERR_PTR(ret);
 }