[libvirt] [PATCH 3/5] storage: Add TRIM algorithm to storage volume API

[Wido den Hollander]

This new algorithm adds support for wiping volumes using TRIM.

It does not overwrite all the data in a volume, but it tells the
backing storage pool/driver that all bytes in a volume can be
discarded.

It depends on the backing storage pool how this is handled.

A SCSI backend might send UNMAP commands to remove all data present
on a LUN.

A Ceph backend might use rbd_discard() to instruct the Ceph cluster
that all data on that RBD volume can be discarded.

Signed-off-by: Wido den Hollander <wido at widodh.nl>
---
 include/libvirt/libvirt-storage.h | 3 +++
 src/storage/storage_backend.c     | 4 ++++
 tools/virsh-volume.c              | 2 +-
 tools/virsh.pod                   | 1 +
 4 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/libvirt/libvirt-storage.h b/include/libvirt/libvirt-storage.h
index 2c55c93..232b4d3 100644
--- a/include/libvirt/libvirt-storage.h
+++ b/include/libvirt/libvirt-storage.h
@@ -153,6 +153,9 @@ typedef enum {
 
     VIR_STORAGE_VOL_WIPE_ALG_RANDOM = 8, /* 1-pass random */
 
+    VIR_STORAGE_VOL_WIPE_ALG_TRIM = 9, /* 1-pass, trim all data on the
+                                          volume by using TRIM or DISCARD */
+
 # ifdef VIR_ENUM_SENTINELS
     VIR_STORAGE_VOL_WIPE_ALG_LAST
     /*
diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
index 15e9109..1bb44a7 100644
--- a/src/storage/storage_backend.c
+++ b/src/storage/storage_backend.c
@@ -2065,6 +2065,7 @@ virStorageBackendVolWipeLocal(virConnectPtr conn ATTRIBUTE_UNUSED,
                   VIR_STORAGE_VOL_WIPE_ALG_PFITZNER7 |
                   VIR_STORAGE_VOL_WIPE_ALG_PFITZNER33 |
                   VIR_STORAGE_VOL_WIPE_ALG_RANDOM |
+                  VIR_STORAGE_VOL_WIPE_ALG_TRIM |
                   VIR_STORAGE_VOL_WIPE_ALG_LAST, -1);
 
     VIR_DEBUG("Wiping volume with path '%s' and algorithm %u",
@@ -2112,6 +2113,9 @@ virStorageBackendVolWipeLocal(virConnectPtr conn ATTRIBUTE_UNUSED,
         case VIR_STORAGE_VOL_WIPE_ALG_RANDOM:
             alg_char = "random";
             break;
+        case VIR_STORAGE_VOL_WIPE_ALG_TRIM:
+            alg_char = "trim";
+            break;
         default:
             virReportError(VIR_ERR_INVALID_ARG,
                            _("unsupported algorithm %d"),
diff --git a/tools/virsh-volume.c b/tools/virsh-volume.c
index 661c876..35f0cbd 100644
--- a/tools/virsh-volume.c
+++ b/tools/virsh-volume.c
@@ -906,7 +906,7 @@ static const vshCmdOptDef opts_vol_wipe[] = {
 VIR_ENUM_DECL(virStorageVolWipeAlgorithm)
 VIR_ENUM_IMPL(virStorageVolWipeAlgorithm, VIR_STORAGE_VOL_WIPE_ALG_LAST,
               "zero", "nnsa", "dod", "bsi", "gutmann", "schneier",
-              "pfitzner7", "pfitzner33", "random");
+              "pfitzner7", "pfitzner33", "random", "trim");
 
 static bool
 cmdVolWipe(vshControl *ctl, const vshCmd *cmd)
diff --git a/tools/virsh.pod b/tools/virsh.pod
index e830c59..b259507 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -3546,6 +3546,7 @@ B<Supported algorithms>
   pfitzner7  - Roy Pfitzner's 7-random-pass method: random x7.
   pfitzner33 - Roy Pfitzner's 33-random-pass method: random x33.
   random     - 1-pass pattern: random.
+  trim       - 1-pass trimming the volume using TRIM or DISCARD
 
 B<Note>: The availability of algorithms may be limited by the version
 of the C<scrub> binary installed on the host.
-- 
1.9.1