btrfs: promote extent_read_full_page to btrfs_readpage

Now that btrfs_readpage is the only caller of extent_read_full_page the
latter can be open coded in the former. Use the occassion to rename
__extent_read_full_page to extent_read_full_page. To facillitate this
change submit_one_bio has to be exported as well.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -160,7 +160,7 @@ static int add_extent_changeset(struct extent_state *state, unsigned bits,
 	return ret;
 }
 
-static int __must_check submit_one_bio(struct bio *bio, int mirror_num,
+int __must_check submit_one_bio(struct bio *bio, int mirror_num,
 				unsigned long bio_flags)
 {
 	blk_status_t ret = 0;
@@ -3365,9 +3365,8 @@ static inline void contiguous_readpages(struct page *pages[], int nr_pages,
 	}
 }
 
-static int __extent_read_full_page(struct page *page, struct bio **bio,
-				   int mirror_num, unsigned long *bio_flags,
-				   unsigned int read_flags)
+int extent_read_full_page(struct page *page, struct bio **bio, int mirror_num,
+			  unsigned long *bio_flags, unsigned int read_flags)
 {
 	struct btrfs_inode *inode = BTRFS_I(page->mapping->host);
 	u64 start = page_offset(page);
@@ -3381,18 +3380,6 @@ static int __extent_read_full_page(struct page *page, struct bio **bio,
 	return ret;
 }
 
-int extent_read_full_page(struct page *page)
-{
-	struct bio *bio = NULL;
-	unsigned long bio_flags = 0;
-	int ret;
-
-	ret = __extent_read_full_page(page, &bio, 0, &bio_flags, 0);
-	if (bio)
-		ret = submit_one_bio(bio, 0, bio_flags);
-	return ret;
-}
-
 static void update_nr_written(struct writeback_control *wbc,
 			      unsigned long nr_written)
 {

fs/btrfs/extent_io.h

@@ -193,7 +193,10 @@ typedef struct extent_map *(get_extent_t)(struct btrfs_inode *inode,
 int try_release_extent_mapping(struct page *page, gfp_t mask);
 int try_release_extent_buffer(struct page *page);
 
-int extent_read_full_page(struct page *page);
+int __must_check submit_one_bio(struct bio *bio, int mirror_num,
+				unsigned long bio_flags);
+int extent_read_full_page(struct page *page, struct bio **bio, int mirror_num,
+			  unsigned long *bio_flags, unsigned int read_flags);
 int extent_write_full_page(struct page *page, struct writeback_control *wbc);
 int extent_write_locked_range(struct inode *inode, u64 start, u64 end,
 			      int mode);

fs/btrfs/inode.c

@@ -8040,7 +8040,14 @@ static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 
 int btrfs_readpage(struct file *file, struct page *page)
 {
-	return extent_read_full_page(page);
+	struct bio *bio = NULL;
+	unsigned long bio_flags = 0;
+	int ret;
+
+	ret = extent_read_full_page(page, &bio, 0, &bio_flags, 0);
+	if (bio)
+		ret = submit_one_bio(bio, 0, bio_flags);
+	return ret;
 }
 
 static int btrfs_writepage(struct page *page, struct writeback_control *wbc)