btrfs: pre-load data checksum for reads in btrfs_submit_bio

Instead of calling btrfs_lookup_bio_sums in every caller of
btrfs_submit_bio that reads data, do the call once in btrfs_submit_bio.
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/bio.c

@@ -14,6 +14,7 @@
 #include "dev-replace.h"
 #include "rcu-string.h"
 #include "zoned.h"
+#include "file-item.h"
 
 static struct bio_set btrfs_bioset;
 
@@ -253,9 +254,16 @@ void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror
 		BUG();
 	}
 
-	/* Save the iter for the end_io handler for data reads. */
-	if (bio_op(bio) == REQ_OP_READ && !(bio->bi_opf & REQ_META))
+	/*
+	 * Save the iter for the end_io handler and preload the checksums for
+	 * data reads.
+	 */
+	if (bio_op(bio) == REQ_OP_READ && !(bio->bi_opf & REQ_META)) {
 		bbio->iter = bio->bi_iter;
+		ret = btrfs_lookup_bio_sums(bbio);
+		if (ret)
+			goto fail;
+	}
 
 	if (!bioc) {
 		/* Single mirror read/write fast path */

fs/btrfs/compression.c

@@ -797,12 +797,6 @@ void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 			 */
 			btrfs_bio(comp_bio)->file_offset = file_offset;
 
-			ret = btrfs_lookup_bio_sums(btrfs_bio(comp_bio));
-			if (ret) {
-				btrfs_bio_end_io(btrfs_bio(comp_bio), ret);
-				break;
-			}
-
 			ASSERT(comp_bio->bi_iter.bi_size);
 			btrfs_submit_bio(fs_info, comp_bio, mirror_num);
 			comp_bio = NULL;

fs/btrfs/inode.c

@@ -2762,7 +2762,6 @@ void btrfs_submit_data_read_bio(struct btrfs_inode *inode, struct bio *bio,
 			int mirror_num, enum btrfs_compression_type compress_type)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
-	blk_status_t ret;
 
 	if (compress_type != BTRFS_COMPRESS_NONE) {
 		/*
@@ -2773,16 +2772,6 @@ void btrfs_submit_data_read_bio(struct btrfs_inode *inode, struct bio *bio,
 		return;
 	}
 
-	/*
-	 * Lookup bio sums does extra checks around whether we need to csum or
-	 * not, which is why we ignore skip_sum here.
-	 */
-	ret = btrfs_lookup_bio_sums(btrfs_bio(bio));
-	if (ret) {
-		btrfs_bio_end_io(btrfs_bio(bio), ret);
-		return;
-	}
-
 	btrfs_submit_bio(fs_info, bio, mirror_num);
 }
 
@@ -8004,12 +7993,6 @@ static void btrfs_submit_dio_bio(struct bio *bio, struct btrfs_inode *inode,
 			btrfs_bio_end_io(btrfs_bio(bio), ret);
 			return;
 		}
-	} else {
-		ret = btrfs_lookup_bio_sums(btrfs_bio(bio));
-		if (ret) {
-			btrfs_bio_end_io(btrfs_bio(bio), ret);
-			return;
-		}
 	}
 map:
 	btrfs_submit_bio(fs_info, bio, 0);
@@ -10269,13 +10252,6 @@ static blk_status_t submit_encoded_read_bio(struct btrfs_inode *inode,
 {
 	struct btrfs_encoded_read_private *priv = btrfs_bio(bio)->private;
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
-	blk_status_t ret;
-
-	if (!priv->skip_csum) {
-		ret = btrfs_lookup_bio_sums(btrfs_bio(bio));
-		if (ret)
-			return ret;
-	}
 
 	atomic_inc(&priv->pending);
 	btrfs_submit_bio(fs_info, bio, mirror_num);