commit ccc0b45917fa76a77ff83f1ddfd30836c8c3805e
Author: Chunyan Liu <cyliu@suse.com>
Date:   Wed May 7 12:45:40 2014 +0800

    add nocow to vol xml
    
    Updated patch. Rebase to git master.
    
    Signed-off-by: Chunyan Liu <cyliu@suse.com>

Index: libvirt-1.2.6/docs/schemas/storagevol.rng
===================================================================
--- libvirt-1.2.6.orig/docs/schemas/storagevol.rng
+++ libvirt-1.2.6/docs/schemas/storagevol.rng
@@ -138,6 +138,11 @@
           <ref name='compat'/>
         </optional>
         <optional>
+          <element name='nocow'>
+            <empty/>
+          </element>
+        </optional>
+        <optional>
           <ref name='fileFormatFeatures'/>
         </optional>
       </interleave>
Index: libvirt-1.2.6/src/conf/storage_conf.c
===================================================================
--- libvirt-1.2.6.orig/src/conf/storage_conf.c
+++ libvirt-1.2.6/src/conf/storage_conf.c
@@ -1397,6 +1397,9 @@ virStorageVolDefParseXML(virStoragePoolD
         virStringFreeList(version);
     }
 
+    if (virXPathNode("./target/nocow", ctxt))
+        ret->target.nocow = true;
+
     if (options->featureFromString && virXPathNode("./target/features", ctxt)) {
         if ((n = virXPathNodeSet("./target/features/*", ctxt, &nodes)) < 0)
             goto error;
Index: libvirt-1.2.6/src/storage/storage_backend.c
===================================================================
--- libvirt-1.2.6.orig/src/storage/storage_backend.c
+++ libvirt-1.2.6/src/storage/storage_backend.c
@@ -37,6 +37,9 @@
 #ifdef __linux__
 # include <sys/ioctl.h>
 # include <linux/fs.h>
+# ifndef FS_NOCOW_FL
+#  define FS_NOCOW_FL                     0x00800000 /* Do not cow file */
+# endif
 #endif
 
 #if WITH_SELINUX
@@ -452,6 +455,21 @@ virStorageBackendCreateRaw(virConnectPtr
         goto cleanup;
     }
 
+    if (vol->target.nocow) {
+#ifdef __linux__
+        int attr;
+
+        /* Set NOCOW flag. This is an optimisation for btrfs.
+         * The FS_IOC_SETFLAGS ioctl return value will be ignored since any
+         * failure of this operation should not block the left work.
+         */
+        if (ioctl(fd, FS_IOC_GETFLAGS, &attr) == 0) {
+            attr |= FS_NOCOW_FL;
+            ioctl(fd, FS_IOC_SETFLAGS, &attr);
+        }
+#endif
+    }
+
     if ((ret = createRawFile(fd, vol, inputvol)) < 0)
         /* createRawFile already reported the exact error. */
         ret = -1;
@@ -717,6 +735,7 @@ virStorageBackendCreateQemuImgOpts(char
                                    bool preallocate,
                                    int format,
                                    const char *compat,
+                                   bool nocow,
                                    virBitmapPtr features)
 {
     virBuffer buf = VIR_BUFFER_INITIALIZER;
@@ -729,6 +748,8 @@ virStorageBackendCreateQemuImgOpts(char
         virBufferAddLit(&buf, "encryption=on,");
     if (preallocate)
         virBufferAddLit(&buf, "preallocation=metadata,");
+    if (nocow)
+        virBufferAddLit(&buf, "nocow=on,");
 
     if (compat)
         virBufferAsprintf(&buf, "compat=%s,", compat);
@@ -950,6 +971,7 @@ virStorageBackendCreateQemuImgCmd(virCon
                                                do_encryption, preallocate,
                                                vol->target.format,
                                                compat,
+                                               vol->target.nocow,
                                                vol->target.features) < 0) {
             virCommandFree(cmd);
             return NULL;
Index: libvirt-1.2.6/src/util/virstoragefile.h
===================================================================
--- libvirt-1.2.6.orig/src/util/virstoragefile.h
+++ libvirt-1.2.6/src/util/virstoragefile.h
@@ -232,6 +232,7 @@ struct _virStorageSource {
                  * pool-specific enum for storage volumes */
     virBitmapPtr features;
     char *compat;
+    bool nocow;
 
     virStoragePermsPtr perms;
     virStorageTimestampsPtr timestamps;