block: Add a disk flag to block integrity profile

So far we have relied on the app tag size to determine whether a disk
has been formatted with T10 protection information or not. However, not
all target devices provide application tag storage.

Add a flag to the block integrity profile that indicates whether the
disk has been formatted with protection information.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Sagi Grimberg <sagig@dev.mellanox.co.il>
Signed-off-by: Jens Axboe <axboe@fb.com>

4 files changed, 28 insertions, 1 deletions

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index 279da08f7541..8df003963d99 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -53,6 +53,14 @@ Description:
                 512 bytes of data.
 
 
+What:           /sys/block/<disk>/integrity/device_is_integrity_capable
+Date:           July 2014
+Contact:        Martin K. Petersen <martin.petersen@oracle.com>
+Description:
+                Indicates whether a storage device is capable of storing
+                integrity metadata. Set if the device is T10 PI-capable.
+
+
 What:           /sys/block/<disk>/integrity/write_generate
 Date:           June 2008
 Contact:        Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/block/blk-integrity.c b/block/blk-integrity.c
index a7436ccc936b..1c6ba442cd91 100644
--- a/block/blk-integrity.c
+++ b/block/blk-integrity.c
@@ -307,6 +307,12 @@ static ssize_t integrity_generate_show(struct blk_integrity *bi, char *page)
         return sprintf(page, "%d\n", (bi->flags & BLK_INTEGRITY_GENERATE) != 0);
 }
 
+static ssize_t integrity_device_show(struct blk_integrity *bi, char *page)
+{
+        return sprintf(page, "%u\n",
+                       (bi->flags & BLK_INTEGRITY_DEVICE_CAPABLE) != 0);
+}
+
 static struct integrity_sysfs_entry integrity_format_entry = {
         .attr = { .name = "format", .mode = S_IRUGO },
         .show = integrity_format_show,
@@ -329,11 +335,17 @@ static struct integrity_sysfs_entry integrity_generate_entry = {
         .store = integrity_generate_store,
 };
 
+static struct integrity_sysfs_entry integrity_device_entry = {
+        .attr = { .name = "device_is_integrity_capable", .mode = S_IRUGO },
+        .show = integrity_device_show,
+};
+
 static struct attribute *integrity_attrs[] = {
         &integrity_format_entry.attr,
         &integrity_tag_size_entry.attr,
         &integrity_verify_entry.attr,
         &integrity_generate_entry.attr,
+        &integrity_device_entry.attr,
         NULL,
 };
 
diff --git a/drivers/scsi/sd_dif.c b/drivers/scsi/sd_dif.c
index 801c41851a01..1e971c6f8c2b 100644
--- a/drivers/scsi/sd_dif.c
+++ b/drivers/scsi/sd_dif.c
@@ -270,7 +270,13 @@ void sd_dif_config_host(struct scsi_disk *sdkp)
                   "Enabling DIX %s protection\n", disk->integrity->name);
 
         /* Signal to block layer that we support sector tagging */
-        if (dif && type && sdkp->ATO) {
+        if (dif && type) {
+
+                disk->integrity->flags |= BLK_INTEGRITY_DEVICE_CAPABLE;
+
+                if (!sdkp)
+                        return;
+
                 if (type == SD_DIF_TYPE3_PROTECTION)
                         disk->integrity->tag_size = sizeof(u16) + sizeof(u32);
                 else
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index cf92eb031ae9..4600fc63e3fc 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1461,6 +1461,7 @@ static inline uint64_t rq_io_start_time_ns(struct request *req)
 enum blk_integrity_flags {
         BLK_INTEGRITY_VERIFY            = 1 << 0,
         BLK_INTEGRITY_GENERATE          = 1 << 1,
+        BLK_INTEGRITY_DEVICE_CAPABLE    = 1 << 2,
 };
 
 struct blk_integrity_iter {