btrfs: sink mirror_num argument in extent_read_full_page

It's always set to 0 from the sole caller - btrfs_readpage.
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

@@ -3365,7 +3365,7 @@ static inline void contiguous_readpages(struct page *pages[], int nr_pages,
 	}
 }
 
-int extent_read_full_page(struct page *page, struct bio **bio, int mirror_num,
+int extent_read_full_page(struct page *page, struct bio **bio,
 			  unsigned long *bio_flags, unsigned int read_flags)
 {
 	struct btrfs_inode *inode = BTRFS_I(page->mapping->host);
@@ -3375,8 +3375,7 @@ int extent_read_full_page(struct page *page, struct bio **bio, int mirror_num,
 
 	btrfs_lock_and_flush_ordered_range(inode, start, end, NULL);
 
-	ret = __do_readpage(page, NULL, bio, mirror_num, bio_flags, read_flags,
-			    NULL);
+	ret = __do_readpage(page, NULL, bio, 0, bio_flags, read_flags, NULL);
 	return ret;
 }
 

fs/btrfs/extent_io.h

@@ -195,7 +195,7 @@ int try_release_extent_buffer(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,
+int extent_read_full_page(struct page *page, struct bio **bio,
 			  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,

fs/btrfs/inode.c

@@ -8044,7 +8044,7 @@ int btrfs_readpage(struct file *file, struct page *page)
 	unsigned long bio_flags = 0;
 	int ret;
 
-	ret = extent_read_full_page(page, &bio, 0, &bio_flags, 0);
+	ret = extent_read_full_page(page, &bio, &bio_flags, 0);
 	if (bio)
 		ret = submit_one_bio(bio, 0, bio_flags);
 	return ret;