[RFC 3/3] btrfs: add checksum offload

[Kanchan Joshi <joshi.k@samsung.com>]

Add new mount option 'datsum_offload'.

When passed
- Data checksumming at the FS level is disabled.
- Data checksumming at the device level is enabled. This is done by
setting REQ_INTEGRITY_OFFLOAD flag for data I/O if the underlying device is
capable.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
---
 fs/btrfs/bio.c   | 12 ++++++++++++
 fs/btrfs/fs.h    |  1 +
 fs/btrfs/super.c |  9 +++++++++
 3 files changed, 22 insertions(+)

diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c
index 7ea6f0b43b95..811d89c64991 100644
--- a/fs/btrfs/bio.c
+++ b/fs/btrfs/bio.c
@@ -5,6 +5,7 @@
  */
 
 #include <linux/bio.h>
+#include <linux/blk-integrity.h>
 #include "bio.h"
 #include "ctree.h"
 #include "volumes.h"
@@ -424,6 +425,15 @@ static void btrfs_clone_write_end_io(struct bio *bio)
 	bio_put(bio);
 }
 
+static void btrfs_prep_csum_offload_hw(struct btrfs_device *dev, struct bio *bio)
+{
+	struct blk_integrity *bi = blk_get_integrity(bio->bi_bdev->bd_disk);
+
+	if (btrfs_test_opt(dev->fs_info, DATASUM_OFFLOAD) &&
+	    bi && bi->offload_type != BLK_INTEGRITY_OFFLOAD_NONE)
+		bio->bi_opf |= REQ_INTEGRITY_OFFLOAD;
+}
+
 static void btrfs_submit_dev_bio(struct btrfs_device *dev, struct bio *bio)
 {
 	if (!dev || !dev->bdev ||
@@ -435,6 +445,8 @@ static void btrfs_submit_dev_bio(struct btrfs_device *dev, struct bio *bio)
 	}
 
 	bio_set_dev(bio, dev->bdev);
+	if (!(bio->bi_opf & REQ_META))
+		btrfs_prep_csum_offload_hw(dev, bio);
 
 	/*
 	 * For zone append writing, bi_sector must point the beginning of the
diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index 79a1a3d6f04d..88e493967100 100644
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -228,6 +228,7 @@ enum {
 	BTRFS_MOUNT_NOSPACECACHE		= (1ULL << 30),
 	BTRFS_MOUNT_IGNOREMETACSUMS		= (1ULL << 31),
 	BTRFS_MOUNT_IGNORESUPERFLAGS		= (1ULL << 32),
+	BTRFS_MOUNT_DATASUM_OFFLOAD		= (1ULL << 33),
 };
 
 /*
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 7dfe5005129a..d0d5b35c2df9 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -121,6 +121,7 @@ enum {
 	Opt_treelog,
 	Opt_user_subvol_rm_allowed,
 	Opt_norecovery,
+	Opt_datasum_offload,
 
 	/* Rescue options */
 	Opt_rescue,
@@ -223,6 +224,7 @@ static const struct fs_parameter_spec btrfs_fs_parameters[] = {
 	fsparam_string("compress-force", Opt_compress_force_type),
 	fsparam_flag_no("datacow", Opt_datacow),
 	fsparam_flag_no("datasum", Opt_datasum),
+	fsparam_flag_no("datasum_offload", Opt_datasum_offload),
 	fsparam_flag("degraded", Opt_degraded),
 	fsparam_string("device", Opt_device),
 	fsparam_flag_no("discard", Opt_discard),
@@ -323,6 +325,10 @@ static int btrfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 			btrfs_clear_opt(ctx->mount_opt, NODATASUM);
 		}
 		break;
+	case Opt_datasum_offload:
+		btrfs_set_opt(ctx->mount_opt, NODATASUM);
+		btrfs_set_opt(ctx->mount_opt, DATASUM_OFFLOAD);
+		break;
 	case Opt_datacow:
 		if (result.negated) {
 			btrfs_clear_opt(ctx->mount_opt, COMPRESS);
@@ -1057,6 +1063,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",degraded");
 	if (btrfs_test_opt(info, NODATASUM))
 		seq_puts(seq, ",nodatasum");
+	if (btrfs_test_opt(info, DATASUM_OFFLOAD))
+		seq_puts(seq, ",datasum_offload");
 	if (btrfs_test_opt(info, NODATACOW))
 		seq_puts(seq, ",nodatacow");
 	if (btrfs_test_opt(info, NOBARRIER))
@@ -1434,6 +1442,7 @@ static void btrfs_emit_options(struct btrfs_fs_info *info,
 	btrfs_info_if_set(info, old, NODATASUM, "setting nodatasum");
 	btrfs_info_if_set(info, old, DEGRADED, "allowing degraded mounts");
 	btrfs_info_if_set(info, old, NODATASUM, "setting nodatasum");
+	btrfs_info_if_set(info, old, DATASUM_OFFLOAD, "setting datasum offload to the device");
 	btrfs_info_if_set(info, old, SSD, "enabling ssd optimizations");
 	btrfs_info_if_set(info, old, SSD_SPREAD, "using spread ssd allocation scheme");
 	btrfs_info_if_set(info, old, NOBARRIER, "turning off barriers");
-- 
2.25.1