[PATCH 11/15] btrfs: put direct I/O checksums in btrfs_dio_private instead of bio

[Omar Sandoval <osandov@osandov.com>]

From: Omar Sandoval <osandov@fb.com>

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 those in btrfs_dio_private and get rid of the awkward
logic that looks up the checksums for orig_bio when the first split bio
is submitted. (Interestingly, btrfs_dio_private did contain the
checksums before commit 23ea8e5a0767 ("Btrfs: load checksum data once
when submitting a direct read io"), but it didn't look them up up
front.)

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 fs/btrfs/inode.c | 79 ++++++++++++++++++++++++------------------------
 1 file changed, 39 insertions(+), 40 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a7fb0ba8cde4..4a2e44f3e66e 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -84,6 +84,9 @@ struct btrfs_dio_private {
 	 */
 	blk_status_t (*subio_endio)(struct inode *, struct btrfs_io_bio *,
 			blk_status_t);
+
+	/* Checksums. */
+	u8 sums[];
 };
 
 struct btrfs_dio_data {
@@ -7753,7 +7756,6 @@ 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);
 }
 
@@ -7865,39 +7867,6 @@ 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)
 {
@@ -7933,10 +7902,12 @@ 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;
+		u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+		size_t csum_offset;
+
+		csum_offset = ((file_offset - dip->logical_offset) >>
+			       inode->i_sb->s_blocksize_bits) * csum_size;
+		btrfs_io_bio(bio)->csum = dip->sums + csum_offset;
 	}
 map:
 	ret = btrfs_map_bio(fs_info, bio, 0);
@@ -8047,13 +8018,25 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
 				loff_t file_offset)
 {
 	struct btrfs_dio_private *dip = NULL;
+	size_t dip_size;
 	struct bio *bio = NULL;
 	struct btrfs_io_bio *io_bio;
 	bool write = (bio_op(dio_bio) == REQ_OP_WRITE);
+	const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);
 
 	bio = btrfs_bio_clone(dio_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);
+		u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+		size_t 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) {
 		if (!write) {
 			unlock_extent(&BTRFS_I(inode)->io_tree, file_offset,
@@ -8093,11 +8076,27 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
 			dip->bytes;
 		dio_data->unsubmitted_oe_range_start =
 			dio_data->unsubmitted_oe_range_end;
-
 		bio->bi_end_io = btrfs_endio_direct_write;
 	} else {
 		bio->bi_end_io = btrfs_endio_direct_read;
 		dip->subio_endio = btrfs_subio_endio_read;
+
+		if (csum) {
+			blk_status_t status;
+
+			/*
+			 * 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->sums);
+			if (status != BLK_STS_OK) {
+				dip->errors = 1;
+				if (refcount_dec_and_test(&dip->refs))
+					bio_io_error(dip->orig_bio);
+				return;
+			}
+		}
 	}
 
 	btrfs_submit_direct_hook(dip);
-- 
2.25.1