btrfs: centralize setting REQ_META

Set REQ_META in btrfs_submit_metadata_bio instead of the various callers.
We'll start relying on this flag inside of btrfs in a bit, and this
ensures it is always set correctly.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -914,6 +914,8 @@ void btrfs_submit_metadata_bio(struct inode *inode, struct bio *bio, int mirror_
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	blk_status_t ret;
 
+	bio->bi_opf |= REQ_META;
+
 	if (btrfs_op(bio) != BTRFS_MAP_WRITE) {
 		/*
 		 * called for a read, do the setup so that checksum validation

fs/btrfs/extent_io.c

@@ -4567,7 +4567,7 @@ static int write_one_subpage_eb(struct extent_buffer *eb,
 {
 	struct btrfs_fs_info *fs_info = eb->fs_info;
 	struct page *page = eb->pages[0];
-	unsigned int write_flags = wbc_to_write_flags(wbc) | REQ_META;
+	unsigned int write_flags = wbc_to_write_flags(wbc);
 	bool no_dirty_ebs = false;
 	int ret;
 
@@ -4612,7 +4612,7 @@ static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
 {
 	u64 disk_bytenr = eb->start;
 	int i, num_pages;
-	unsigned int write_flags = wbc_to_write_flags(wbc) | REQ_META;
+	unsigned int write_flags = wbc_to_write_flags(wbc);
 	int ret = 0;
 
 	prepare_eb_write(eb);
@@ -6630,7 +6630,7 @@ static int read_extent_buffer_subpage(struct extent_buffer *eb, int wait,
 	btrfs_subpage_clear_error(fs_info, page, eb->start, eb->len);
 
 	btrfs_subpage_start_reader(fs_info, page, eb->start, eb->len);
-	ret = submit_extent_page(REQ_OP_READ | REQ_META, NULL, &bio_ctrl,
+	ret = submit_extent_page(REQ_OP_READ, NULL, &bio_ctrl,
 				 page, eb->start, eb->len,
 				 eb->start - page_offset(page),
 				 end_bio_extent_readpage, mirror_num, 0,
@@ -6737,7 +6737,7 @@ int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num)
 			}
 
 			ClearPageError(page);
-			err = submit_extent_page(REQ_OP_READ | REQ_META, NULL,
+			err = submit_extent_page(REQ_OP_READ, NULL,
 					 &bio_ctrl, page, page_offset(page),
 					 PAGE_SIZE, 0, end_bio_extent_readpage,
 					 mirror_num, 0, false);