gluster: add support for PREALLOC_MODE_FALLOC

Add missing support for "preallocation=falloc" to the Gluster block
driver. This change bases its logic on that of block/file-posix.c and
removed the gluster_supports_zerofill() and qemu_gluster_zerofill()
functions in favour of #ifdef checks in an easy to read
switch-statement.

Both glfs_zerofill() and glfs_fallocate() have been introduced with
GlusterFS 3.5.0 (pkg-config glusterfs-api = 6). A #define for the
availability of glfs_fallocate() has been added to ./configure.

Reported-by: Satheesaran Sundaramoorthi <sasundar@redhat.com>
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Message-id: 20170528063114.28691-1-ndevos@redhat.com
URL: https://bugzilla.redhat.com/1450759
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>

block/gluster.c

@@ -964,29 +964,6 @@ static coroutine_fn int qemu_gluster_co_pwrite_zeroes(BlockDriverState *bs,
     qemu_coroutine_yield();
     return acb.ret;
 }
-
-static inline bool gluster_supports_zerofill(void)
-{
-    return 1;
-}
-
-static inline int qemu_gluster_zerofill(struct glfs_fd *fd, int64_t offset,
-                                        int64_t size)
-{
-    return glfs_zerofill(fd, offset, size);
-}
-
-#else
-static inline bool gluster_supports_zerofill(void)
-{
-    return 0;
-}
-
-static inline int qemu_gluster_zerofill(struct glfs_fd *fd, int64_t offset,
-                                        int64_t size)
-{
-    return 0;
-}
 #endif
 
 static int qemu_gluster_create(const char *filename,
@@ -996,9 +973,10 @@ static int qemu_gluster_create(const char *filename,
     struct glfs *glfs;
     struct glfs_fd *fd;
     int ret = 0;
-    int prealloc = 0;
+    PreallocMode prealloc;
     int64_t total_size = 0;
     char *tmp = NULL;
+    Error *local_err = NULL;
 
     gconf = g_new0(BlockdevOptionsGluster, 1);
     gconf->debug = qemu_opt_get_number_del(opts, GLUSTER_OPT_DEBUG,
@@ -1026,13 +1004,12 @@ static int qemu_gluster_create(const char *filename,
                           BDRV_SECTOR_SIZE);
 
     tmp = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
-    if (!tmp || !strcmp(tmp, "off")) {
-        prealloc = 0;
-    } else if (!strcmp(tmp, "full") && gluster_supports_zerofill()) {
-        prealloc = 1;
-    } else {
-        error_setg(errp, "Invalid preallocation mode: '%s'"
-                         " or GlusterFS doesn't support zerofill API", tmp);
+    prealloc = qapi_enum_parse(PreallocMode_lookup, tmp,
+                               PREALLOC_MODE__MAX, PREALLOC_MODE_OFF,
+                               &local_err);
+    g_free(tmp);
+    if (local_err) {
+        error_propagate(errp, local_err);
         ret = -EINVAL;
         goto out;
     }
@@ -1041,21 +1018,48 @@ static int qemu_gluster_create(const char *filename,
                     O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, S_IRUSR | S_IWUSR);
     if (!fd) {
         ret = -errno;
-    } else {
+        goto out;
+    }
+
+    switch (prealloc) {
+#ifdef CONFIG_GLUSTERFS_FALLOCATE
+    case PREALLOC_MODE_FALLOC:
+        if (glfs_fallocate(fd, 0, 0, total_size)) {
+            error_setg(errp, "Could not preallocate data for the new file");
+            ret = -errno;
+        }
+        break;
+#endif /* CONFIG_GLUSTERFS_FALLOCATE */
+#ifdef CONFIG_GLUSTERFS_ZEROFILL
+    case PREALLOC_MODE_FULL:
         if (!glfs_ftruncate(fd, total_size)) {
-            if (prealloc && qemu_gluster_zerofill(fd, 0, total_size)) {
+            if (glfs_zerofill(fd, 0, total_size)) {
+                error_setg(errp, "Could not zerofill the new file");
                 ret = -errno;
             }
         } else {
+            error_setg(errp, "Could not resize file");
             ret = -errno;
         }
-
-        if (glfs_close(fd) != 0) {
+        break;
+#endif /* CONFIG_GLUSTERFS_ZEROFILL */
+    case PREALLOC_MODE_OFF:
+        if (glfs_ftruncate(fd, total_size) != 0) {
             ret = -errno;
+            error_setg(errp, "Could not resize file");
         }
+        break;
+    default:
+        ret = -EINVAL;
+        error_setg(errp, "Unsupported preallocation mode: %s",
+                   PreallocMode_lookup[prealloc]);
+        break;
+    }
+
+    if (glfs_close(fd) != 0) {
+        ret = -errno;
     }
 out:
-    g_free(tmp);
     qapi_free_BlockdevOptionsGluster(gconf);
     glfs_clear_preopened(glfs);
     return ret;

configure

@@ -300,6 +300,7 @@ seccomp=""
 glusterfs=""
 glusterfs_xlator_opt="no"
 glusterfs_discard="no"
+glusterfs_fallocate="no"
 glusterfs_zerofill="no"
 gtk=""
 gtkabi=""
@@ -3583,6 +3584,7 @@ if test "$glusterfs" != "no" ; then
       glusterfs_discard="yes"
     fi
     if $pkg_config --atleast-version=6 glusterfs-api; then
+      glusterfs_fallocate="yes"
       glusterfs_zerofill="yes"
     fi
   else
@@ -5757,6 +5759,10 @@ if test "$glusterfs_discard" = "yes" ; then
   echo "CONFIG_GLUSTERFS_DISCARD=y" >> $config_host_mak
 fi
 
+if test "$glusterfs_fallocate" = "yes" ; then
+  echo "CONFIG_GLUSTERFS_FALLOCATE=y" >> $config_host_mak
+fi
+
 if test "$glusterfs_zerofill" = "yes" ; then
   echo "CONFIG_GLUSTERFS_ZEROFILL=y" >> $config_host_mak
 fi