virstoragefile: Have virStorageFileResize use safezero

Currently virStorageFileResize() function uses build conditionals to
choose either the posix_fallocate() or syscall(SYS_fallocate) with no
fallback in order to preallocate the space in the newly resized file.

Since the safezero code has a similar set of conditionals modify the
resize and safezero code in order to allow the resize logic to make use
of safezero to unify the look/feel of the code paths.

Add a new boolean (resize) to safezero() to make the optional decision
whether to try syscall(SYS_fallocate) if the posix_fallocate fails because
HAVE_POSIX_FALLOCATE is not defined (eg, return -1 and errno == 0).

Create a local safezero_sys_fallocate in order to handle the resize
code paths that support that.  If not present, the set errno = ENOSYS
in order to allow the caller to handle the failure scenarios.

Signed-off-by: John Ferlan <jferlan@redhat.com>

src/locking/lock_driver_sanlock.c

@@ -281,7 +281,7 @@ static int virLockManagerSanlockSetupLockspace(void)
             /*
              * Pre allocate enough data for 1 block of leases at preferred alignment
              */
-            if (safezero(fd, 0, rv) < 0) {
+            if (safezero(fd, 0, rv, false) < 0) {
                 virReportSystemError(errno,
                                      _("Unable to allocate lockspace %s"),
                                      path);
@@ -690,7 +690,7 @@ static int virLockManagerSanlockCreateLease(struct sanlk_resource *res)
             /*
              * Pre allocate enough data for 1 block of leases at preferred alignment
              */
-            if (safezero(fd, 0, rv) < 0) {
+            if (safezero(fd, 0, rv, false) < 0) {
                 virReportSystemError(errno,
                                      _("Unable to allocate lease %s"),
                                      res->disks[0].path);

src/storage/storage_backend.c

@@ -399,7 +399,7 @@ createRawFile(int fd, virStorageVolDefPtr vol,
     }
 
     if (remain && need_alloc) {
-        if (safezero(fd, vol->target.allocation - remain, remain) < 0) {
+        if (safezero(fd, vol->target.allocation - remain, remain, false) < 0) {
             ret = -errno;
             virReportSystemError(errno, _("cannot fill file '%s'"),
                                  vol->target.path);

src/util/virfile.c

@@ -42,6 +42,9 @@
 #if HAVE_MMAP
 # include <sys/mman.h>
 #endif
+#if HAVE_SYS_SYSCALL_H
+# include <sys/syscall.h>
+#endif
 
 #ifdef __linux__
 # if HAVE_LINUX_MAGIC_H
@@ -1046,6 +1049,20 @@ safezero_posix_fallocate(int fd, off_t offset, off_t len)
     return -1;
 }
 
+static int
+safezero_sys_fallocate(int fd,
+                       off_t offset,
+                       off_t len)
+{
+    int rc = -1;
+#if HAVE_SYS_SYSCALL_H && defined(SYS_fallocate)
+    rc = syscall(SYS_fallocate, fd, 0, offset, len);
+#else
+    errno = ENOSYS;
+#endif
+    return rc;
+}
+
 static int
 safezero_mmap(int fd, off_t offset, off_t len)
 {
@@ -1119,7 +1136,7 @@ safezero_slow(int fd, off_t offset, off_t len)
     return 0;
 }
 
-int safezero(int fd, off_t offset, off_t len)
+int safezero(int fd, off_t offset, off_t len, bool resize)
 {
     int ret;
 
@@ -1134,6 +1151,9 @@ int safezero(int fd, off_t offset, off_t len)
     if (ret == 0 || errno != 0)
         return ret;
 
+    if (resize)
+        return safezero_sys_fallocate(fd, offset, len);
+
     if (safezero_mmap(fd, offset, len) == 0)
         return 0;
     return safezero_slow(fd, offset, len);

src/util/virfile.h

@@ -41,7 +41,7 @@ typedef enum {
 ssize_t saferead(int fd, void *buf, size_t count) ATTRIBUTE_RETURN_CHECK;
 ssize_t safewrite(int fd, const void *buf, size_t count)
     ATTRIBUTE_RETURN_CHECK;
-int safezero(int fd, off_t offset, off_t len)
+int safezero(int fd, off_t offset, off_t len, bool resize)
     ATTRIBUTE_RETURN_CHECK;
 
 /* Don't call these directly - use the macros below */

src/util/virstoragefile.c

@@ -43,9 +43,6 @@
 #include "viruri.h"
 #include "dirname.h"
 #include "virbuffer.h"
-#if HAVE_SYS_SYSCALL_H
-# include <sys/syscall.h>
-#endif
 
 #define VIR_FROM_THIS VIR_FROM_STORAGE
 
@@ -1120,25 +1117,17 @@ virStorageFileResize(const char *path,
     }
 
     if (pre_allocate) {
-#if HAVE_POSIX_FALLOCATE
-        if ((rc = posix_fallocate(fd, offset, len)) != 0) {
-            virReportSystemError(rc,
-                                 _("Failed to pre-allocate space for "
-                                   "file '%s'"), path);
+        if (safezero(fd, offset, len, true) != 0) {
+            if (errno == ENOSYS)
+                virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                               _("preallocate is not supported on this "
+                                 "platform"));
+            else
+                virReportSystemError(errno,
+                                     _("Failed to pre-allocate space for "
+                                       "file '%s'"), path);
             goto cleanup;
         }
-#elif HAVE_SYS_SYSCALL_H && defined(SYS_fallocate)
-        if (syscall(SYS_fallocate, fd, 0, offset, len) != 0) {
-            virReportSystemError(errno,
-                                 _("Failed to pre-allocate space for "
-                                   "file '%s'"), path);
-            goto cleanup;
-        }
-#else
-        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
-                       _("preallocate is not supported on this platform"));
-        goto cleanup;
-#endif
     } else {
         if (ftruncate(fd, capacity) < 0) {
             virReportSystemError(errno,