btrfs: refactor end_bio_extent_readpage code flow

Untangle the goto and move the code it jumps to so it goes in the order
of the most likely states first.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -3017,7 +3017,6 @@ static void end_bio_extent_readpage(struct bio *bio)
 	 */
 	u32 bio_offset = 0;
 	int mirror;
-	int ret;
 	struct bvec_iter_all iter_all;
 
 	ASSERT(!bio_flagged(bio, BIO_CLONED));
@@ -3028,6 +3027,7 @@ static void end_bio_extent_readpage(struct bio *bio)
 		struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 		const u32 sectorsize = fs_info->sectorsize;
 		unsigned int error_bitmap = (unsigned int)-1;
+		bool repair = false;
 		u64 start;
 		u64 end;
 		u32 len;
@@ -3065,55 +3065,23 @@ static void end_bio_extent_readpage(struct bio *bio)
 			if (is_data_inode(inode)) {
 				error_bitmap = btrfs_verify_data_csum(bbio,
 						bio_offset, page, start, end);
-				ret = error_bitmap;
+				if (error_bitmap)
+					uptodate = false;
 			} else {
-				ret = btrfs_validate_metadata_buffer(bbio,
-					page, start, end, mirror);
+				if (btrfs_validate_metadata_buffer(bbio,
+						page, start, end, mirror))
+					uptodate = false;
 			}
-			if (ret)
-				uptodate = false;
-			else
-				clean_io_failure(BTRFS_I(inode)->root->fs_info,
-						 failure_tree, tree, start,
-						 page,
-						 btrfs_ino(BTRFS_I(inode)), 0);
 		}
 
-		if (likely(uptodate))
-			goto readpage_ok;
-
-		if (is_data_inode(inode)) {
-			/*
-			 * If we failed to submit the IO at all we'll have a
-			 * mirror_num == 0, in which case we need to just mark
-			 * the page with an error and unlock it and carry on.
-			 */
-			if (mirror == 0)
-				goto readpage_ok;
-
-			/*
-			 * submit_data_read_repair() will handle all the good
-			 * and bad sectors, we just continue to the next bvec.
-			 */
-			submit_data_read_repair(inode, bio, bio_offset, bvec,
-						mirror, error_bitmap);
-
-			ASSERT(bio_offset + len > bio_offset);
-			bio_offset += len;
-			continue;
-		} else {
-			struct extent_buffer *eb;
-
-			eb = find_extent_buffer_readpage(fs_info, page, start);
-			set_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
-			eb->read_mirror = mirror;
-			atomic_dec(&eb->io_pages);
-		}
-readpage_ok:
 		if (likely(uptodate)) {
 			loff_t i_size = i_size_read(inode);
 			pgoff_t end_index = i_size >> PAGE_SHIFT;
 
+			clean_io_failure(BTRFS_I(inode)->root->fs_info,
+					 failure_tree, tree, start, page,
+					 btrfs_ino(BTRFS_I(inode)), 0);
+
 			/*
 			 * Zero out the remaining part if this range straddles
 			 * i_size.
@@ -3130,14 +3098,40 @@ static void end_bio_extent_readpage(struct bio *bio)
 				zero_user_segment(page, zero_start,
 						  offset_in_page(end) + 1);
 			}
+		} else if (is_data_inode(inode)) {
+			/*
+			 * Only try to repair bios that actually made it to a
+			 * device.  If the bio failed to be submitted mirror
+			 * is 0 and we need to fail it without retrying.
+			 */
+			if (mirror > 0)
+				repair = true;
+		} else {
+			struct extent_buffer *eb;
+
+			eb = find_extent_buffer_readpage(fs_info, page, start);
+			set_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
+			eb->read_mirror = mirror;
+			atomic_dec(&eb->io_pages);
 		}
+
+		if (repair) {
+			/*
+			 * submit_data_read_repair() will handle all the good
+			 * and bad sectors, we just continue to the next bvec.
+			 */
+			submit_data_read_repair(inode, bio, bio_offset, bvec,
+						mirror, error_bitmap);
+		} else {
+			/* Update page status and unlock */
+			end_page_read(page, uptodate, start, len);
+			endio_readpage_release_extent(&processed, BTRFS_I(inode),
+					start, end, PageUptodate(page));
+		}
+
 		ASSERT(bio_offset + len > bio_offset);
 		bio_offset += len;
 
-		/* Update page status and unlock */
-		end_page_read(page, uptodate, start, len);
-		endio_readpage_release_extent(&processed, BTRFS_I(inode),
-					      start, end, PageUptodate(page));
 	}
 	/* Release the last extent */
 	endio_readpage_release_extent(&processed, NULL, 0, 0, false);