btrfs: put direct I/O checksums in btrfs_dio_private instead of bio

The next commit will get rid of btrfs_dio_private->orig_bio. The only
thing we really need it for is containing all of the checksums, but we
can easily put the checksum array in btrfs_dio_private and have the
submitted bios reference the array. We can also look the checksums up
while we're setting up instead of the current awkward logic that looks
them up for orig_bio when the first split bio is submitted.

(Interestingly, btrfs_dio_private did contain the
checksums before commit 23ea8e5a ("Btrfs: load checksum data once
when submitting a direct read io"), but it didn't look them up up
front.)
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/btrfs_inode.h

@@ -324,6 +324,9 @@ struct btrfs_dio_private {
 	 */
 	blk_status_t (*subio_endio)(struct inode *, struct btrfs_io_bio *,
 			blk_status_t);
+
+	/* Array of checksums */
+	u8 csums[];
 };
 
 /*

fs/btrfs/inode.c

@@ -7712,7 +7712,6 @@ static void btrfs_endio_direct_read(struct bio *bio)
 
 	dio_bio->bi_status = err;
 	dio_end_io(dio_bio);
-	btrfs_io_bio_free_csum(io_bio);
 	bio_put(bio);
 }
 
@@ -7824,39 +7823,6 @@ static void btrfs_end_dio_bio(struct bio *bio)
 	bio_put(bio);
 }
 
-static inline blk_status_t btrfs_lookup_and_bind_dio_csum(struct inode *inode,
-						 struct btrfs_dio_private *dip,
-						 struct bio *bio,
-						 u64 file_offset)
-{
-	struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
-	struct btrfs_io_bio *orig_io_bio = btrfs_io_bio(dip->orig_bio);
-	u16 csum_size;
-	blk_status_t ret;
-
-	/*
-	 * We load all the csum data we need when we submit
-	 * the first bio to reduce the csum tree search and
-	 * contention.
-	 */
-	if (dip->logical_offset == file_offset) {
-		ret = btrfs_lookup_bio_sums(inode, dip->orig_bio, file_offset,
-					    NULL);
-		if (ret)
-			return ret;
-	}
-
-	if (bio == dip->orig_bio)
-		return 0;
-
-	file_offset -= dip->logical_offset;
-	file_offset >>= inode->i_sb->s_blocksize_bits;
-	csum_size = btrfs_super_csum_size(btrfs_sb(inode->i_sb)->super_copy);
-	io_bio->csum = orig_io_bio->csum + csum_size * file_offset;
-
-	return 0;
-}
-
 static inline blk_status_t btrfs_submit_dio_bio(struct bio *bio,
 		struct inode *inode, u64 file_offset, int async_submit)
 {
@@ -7892,10 +7858,12 @@ static inline blk_status_t btrfs_submit_dio_bio(struct bio *bio,
 		if (ret)
 			goto err;
 	} else {
-		ret = btrfs_lookup_and_bind_dio_csum(inode, dip, bio,
-						     file_offset);
-		if (ret)
-			goto err;
+		u64 csum_offset;
+
+		csum_offset = file_offset - dip->logical_offset;
+		csum_offset >>= inode->i_sb->s_blocksize_bits;
+		csum_offset *= btrfs_super_csum_size(fs_info->super_copy);
+		btrfs_io_bio(bio)->csum = dip->csums + csum_offset;
 	}
 map:
 	ret = btrfs_map_bio(fs_info, bio, 0);
@@ -7912,10 +7880,22 @@ static struct btrfs_dio_private *btrfs_create_dio_private(struct bio *dio_bio,
 							  loff_t file_offset)
 {
 	const bool write = (bio_op(dio_bio) == REQ_OP_WRITE);
+	const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);
+	size_t dip_size;
 	struct btrfs_dio_private *dip;
 	struct bio *bio;
 
-	dip = kzalloc(sizeof(*dip), GFP_NOFS);
+	dip_size = sizeof(*dip);
+	if (!write && csum) {
+		struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+		const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+		size_t nblocks;
+
+		nblocks = dio_bio->bi_iter.bi_size >> inode->i_sb->s_blocksize_bits;
+		dip_size += csum_size * nblocks;
+	}
+
+	dip = kzalloc(dip_size, GFP_NOFS);
 	if (!dip)
 		return NULL;
 
@@ -7955,6 +7935,7 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
 				loff_t file_offset)
 {
 	const bool write = (bio_op(dio_bio) == REQ_OP_WRITE);
+	const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_dio_private *dip;
 	struct bio *bio;
@@ -7979,6 +7960,17 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
 		return;
 	}
 
+	if (!write && csum) {
+		/*
+		 * Load the csums up front to reduce csum tree searches and
+		 * contention when submitting bios.
+		 */
+		status = btrfs_lookup_bio_sums(inode, dio_bio, file_offset,
+					       dip->csums);
+		if (status != BLK_STS_OK)
+			goto out_err;
+	}
+
 	orig_bio = dip->orig_bio;
 	start_sector = orig_bio->bi_iter.bi_sector;
 	submit_len = orig_bio->bi_iter.bi_size;