btrfs: enable experimental large data folio support

With all the preparation patches already merged, it's pretty easy to
enable large data folios:

- Remove the ASSERT() on folio size in btrfs_end_repair_bio()

- Add a helper to properly set the max folio order
  Currently due to several call sites are fetching the bitmap content
  directly into an unsigned long, we can only support BITS_PER_LONG
  blocks for each bitmap.

- Call the helper when reading/creating an inode

The support has the following limits:

- No large folios for data reloc inode
  The relocation code still requires page sized folio.
  But it's not that hot nor common compared to regular buffered ios.

  Will be improved in the future.

- Requires CONFIG_BTRFS_EXPERIMENTAL

Unfortunately I do not have a physical machine for performance test, but
if everything goes like XFS/EXT4, it should mostly bring single digits
percentage performance improvement in the real world.

Although I believe there are still quite some optimizations to be done,
let's focus on testing the current large data folio support first.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: adam900710

fs/btrfs/bio.c

@@ -165,12 +165,6 @@ static void btrfs_end_repair_bio(struct btrfs_bio *repair_bbio,
 	struct bio_vec *bv = bio_first_bvec_all(&repair_bbio->bio);
 	int mirror = repair_bbio->mirror_num;
 
-	/*
-	 * We can only trigger this for data bio, which doesn't support larger
-	 * folios yet.
-	 */
-	ASSERT(folio_order(page_folio(bv->bv_page)) == 0);
-
 	if (repair_bbio->bio.bi_status ||
 	    !btrfs_data_csum_ok(repair_bbio, dev, 0, bv)) {
 		bio_reset(&repair_bbio->bio, NULL, REQ_OP_READ);

fs/btrfs/btrfs_inode.h

@@ -525,6 +525,23 @@ static inline void btrfs_update_inode_mapping_flags(struct btrfs_inode *inode)
 		mapping_set_stable_writes(inode->vfs_inode.i_mapping);
 }
 
+static inline void btrfs_set_inode_mapping_order(struct btrfs_inode *inode)
+{
+	/* Metadata inode should not reach here. */
+	ASSERT(is_data_inode(inode));
+
+	/* For data reloc inode, it still requires page sized folio. */
+	if (unlikely(btrfs_is_data_reloc_root(inode->root)))
+		return;
+
+	/* We only allows BITS_PER_LONGS blocks for each bitmap. */
+#ifdef CONFIG_BTRFS_EXPERIMENTAL
+	mapping_set_folio_order_range(inode->vfs_inode.i_mapping, 0,
+			ilog2(((BITS_PER_LONG << inode->root->fs_info->sectorsize_bits)
+				>> PAGE_SHIFT)));
+#endif
+}
+
 /* Array of bytes with variable length, hexadecimal format 0x1234 */
 #define CSUM_FMT				"0x%*phN"
 #define CSUM_FMT_VALUE(size, bytes)		size, bytes

fs/btrfs/inode.c

@@ -3946,6 +3946,7 @@ static int btrfs_read_locked_inode(struct btrfs_inode *inode, struct btrfs_path
 	btrfs_inode_split_flags(btrfs_inode_flags(leaf, inode_item),
 				&inode->flags, &inode->ro_flags);
 	btrfs_update_inode_mapping_flags(inode);
+	btrfs_set_inode_mapping_order(inode);
 
 cache_index:
 	/*
@@ -6463,6 +6464,7 @@ int btrfs_create_new_inode(struct btrfs_trans_handle *trans,
 			BTRFS_I(inode)->flags |= BTRFS_INODE_NODATACOW |
 				BTRFS_INODE_NODATASUM;
 		btrfs_update_inode_mapping_flags(BTRFS_I(inode));
+		btrfs_set_inode_mapping_order(BTRFS_I(inode));
 	}
 
 	ret = btrfs_insert_inode_locked(inode);