1 files changed, 54 insertions, 9 deletions

diff --git a/fs/bio.c b/fs/bio.c
index 460554b07ff9..7b3069589951 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -126,6 +126,7 @@ static void bio_fs_destructor(struct bio *bio)
 inline void bio_init(struct bio *bio)
 {
         bio->bi_next = NULL;
+        bio->bi_bdev = NULL;
         bio->bi_flags = 1 << BIO_UPTODATE;
         bio->bi_rw = 0;
         bio->bi_vcnt = 0;
@@ -313,7 +314,8 @@ int bio_get_nr_vecs(struct block_device *bdev)
 }
 
 static int __bio_add_page(request_queue_t *q, struct bio *bio, struct page
-                          *page, unsigned int len, unsigned int offset)
+                          *page, unsigned int len, unsigned int offset,
+                          unsigned short max_sectors)
 {
         int retried_segments = 0;
         struct bio_vec *bvec;
@@ -324,10 +326,31 @@ static int __bio_add_page(request_queue_t *q, struct bio *bio, struct page
         if (unlikely(bio_flagged(bio, BIO_CLONED)))
                 return 0;
 
-        if (bio->bi_vcnt >= bio->bi_max_vecs)
+        if (((bio->bi_size + len) >> 9) > max_sectors)
                 return 0;
 
-        if (((bio->bi_size + len) >> 9) > q->max_sectors)
+        /*
+         * For filesystems with a blocksize smaller than the pagesize
+         * we will often be called with the same page as last time and
+         * a consecutive offset.  Optimize this special case.
+         */
+        if (bio->bi_vcnt > 0) {
+                struct bio_vec *prev = &bio->bi_io_vec[bio->bi_vcnt - 1];
+
+                if (page == prev->bv_page &&
+                    offset == prev->bv_offset + prev->bv_len) {
+                        prev->bv_len += len;
+                        if (q->merge_bvec_fn &&
+                            q->merge_bvec_fn(q, bio, prev) < len) {
+                                prev->bv_len -= len;
+                                return 0;
+                        }
+
+                        goto done;
+                }
+        }
+
+        if (bio->bi_vcnt >= bio->bi_max_vecs)
                 return 0;
 
         /*
@@ -381,11 +404,31 @@ static int __bio_add_page(request_queue_t *q, struct bio *bio, struct page
         bio->bi_vcnt++;
         bio->bi_phys_segments++;
         bio->bi_hw_segments++;
+ done:
         bio->bi_size += len;
         return len;
 }
 
 /**
+ *      bio_add_pc_page -       attempt to add page to bio
+ *      @bio: destination bio
+ *      @page: page to add
+ *      @len: vec entry length
+ *      @offset: vec entry offset
+ *
+ *      Attempt to add a page to the bio_vec maplist. This can fail for a
+ *      number of reasons, such as the bio being full or target block
+ *      device limitations. The target block device must allow bio's
+ *      smaller than PAGE_SIZE, so it is always possible to add a single
+ *      page to an empty bio. This should only be used by REQ_PC bios.
+ */
+int bio_add_pc_page(request_queue_t *q, struct bio *bio, struct page *page,
+                    unsigned int len, unsigned int offset)
+{
+        return __bio_add_page(q, bio, page, len, offset, q->max_hw_sectors);
+}
+
+/**
  *      bio_add_page    -       attempt to add page to bio
  *      @bio: destination bio
  *      @page: page to add
@@ -401,8 +444,8 @@ static int __bio_add_page(request_queue_t *q, struct bio *bio, struct page
 int bio_add_page(struct bio *bio, struct page *page, unsigned int len,
                  unsigned int offset)
 {
-        return __bio_add_page(bdev_get_queue(bio->bi_bdev), bio, page,
-                              len, offset);
+        struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+        return __bio_add_page(q, bio, page, len, offset, q->max_sectors);
 }
 
 struct bio_map_data {
@@ -514,7 +557,7 @@ struct bio *bio_copy_user(request_queue_t *q, unsigned long uaddr,
                         break;
                 }
 
-                if (__bio_add_page(q, bio, page, bytes, 0) < bytes) {
+                if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes) {
                         ret = -EINVAL;
                         break;
                 }
@@ -628,7 +671,8 @@ static struct bio *__bio_map_user_iov(request_queue_t *q,
                         /*
                          * sorry...
                          */
-                        if (__bio_add_page(q, bio, pages[j], bytes, offset) < bytes)
+                        if (bio_add_pc_page(q, bio, pages[j], bytes, offset) <
+                                            bytes)
                                 break;
 
                         len -= bytes;
@@ -801,8 +845,8 @@ static struct bio *__bio_map_kern(request_queue_t *q, void *data,
                 if (bytes > len)
                         bytes = len;
 
-                if (__bio_add_page(q, bio, virt_to_page(data), bytes,
-                                   offset) < bytes)
+                if (bio_add_pc_page(q, bio, virt_to_page(data), bytes,
+                                    offset) < bytes)
                         break;
 
                 data += bytes;
@@ -1228,6 +1272,7 @@ EXPORT_SYMBOL(bio_clone);
 EXPORT_SYMBOL(bio_phys_segments);
 EXPORT_SYMBOL(bio_hw_segments);
 EXPORT_SYMBOL(bio_add_page);
+EXPORT_SYMBOL(bio_add_pc_page);
 EXPORT_SYMBOL(bio_get_nr_vecs);
 EXPORT_SYMBOL(bio_map_user);
 EXPORT_SYMBOL(bio_unmap_user);