block: simplify bio_map_kern

Just open code the trivial mapping from a kernel virtual address to
a bio instead of going through the complex user address mapping
machinery.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 44 insertions, 16 deletions

diff --git a/block/bio.c b/block/bio.c
index 471d7382c7d1..54da51ed43de 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1563,9 +1563,8 @@ static void bio_copy_kern_endio(struct bio *bio, int err)
 {
         struct bio_vec *bvec;
         const int read = bio_data_dir(bio) == READ;
-        struct bio_map_data *bmd = bio->bi_private;
+        char *p = bio->bi_private;
         int i;
-        char *p = bmd->sgvecs[0].iov_base;
 
         bio_for_each_segment_all(bvec, bio, i) {
                 char *addr = page_address(bvec->bv_page);
@@ -1577,7 +1576,6 @@ static void bio_copy_kern_endio(struct bio *bio, int err)
                 p += bvec->bv_len;
         }
 
-        kfree(bmd);
         bio_put(bio);
 }
 
@@ -1595,28 +1593,58 @@ static void bio_copy_kern_endio(struct bio *bio, int err)
 struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
                           gfp_t gfp_mask, int reading)
 {
-        struct bio *bio;
+        unsigned long kaddr = (unsigned long)data;
+        unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+        unsigned long start = kaddr >> PAGE_SHIFT;
         struct bio_vec *bvec;
-        int i;
+        struct bio *bio;
+        void *p = data;
+        int nr_pages = 0, i;
 
-        bio = bio_copy_user(q, NULL, (unsigned long)data, len, 1, gfp_mask);
-        if (IS_ERR(bio))
-                return bio;
+        /*
+         * Overflow, abort
+         */
+        if (end < start)
+                return ERR_PTR(-EINVAL);
 
-        if (!reading) {
-                void *p = data;
+        nr_pages = end - start;
+        bio = bio_kmalloc(gfp_mask, nr_pages);
+        if (!bio)
+                return ERR_PTR(-ENOMEM);
 
-                bio_for_each_segment_all(bvec, bio, i) {
-                        char *addr = page_address(bvec->bv_page);
+        while (len) {
+                struct page *page;
+                unsigned int bytes = PAGE_SIZE;
 
-                        memcpy(addr, p, bvec->bv_len);
-                        p += bvec->bv_len;
-                }
+                if (bytes > len)
+                        bytes = len;
+
+                page = alloc_page(q->bounce_gfp | gfp_mask);
+                if (!page)
+                        goto cleanup;
+
+                if (!reading)
+                        memcpy(page_address(page), p, bytes);
+
+                if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes)
+                        break;
+
+                len -= bytes;
+                p += bytes;
         }
 
-        bio->bi_end_io = bio_copy_kern_endio;
+        if (!reading)
+                bio->bi_rw |= REQ_WRITE;
 
+        bio->bi_private = data;
+        bio->bi_end_io = bio_copy_kern_endio;
         return bio;
+
+cleanup:
+        bio_for_each_segment_all(bvec, bio, i)
+                __free_page(bvec->bv_page);
+        bio_put(bio);
+        return ERR_PTR(-ENOMEM);
 }
 EXPORT_SYMBOL(bio_copy_kern);