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[libvirt] [PATCH] util: allow creation of file with virFileWriteStr



Making this change will allow the future patches to use
virFileWriteStr to create a file, rather than its current limitation
of only working on pre-existing files.

* src/util/util.h (virFileWriteStr): Alter signature.
* src/util/util.c (virFileWriteStr): Allow file creation.
* src/network/bridge_driver.c (networkEnableIpForwarding)
(networkDisableIPV6): Adjust clients.
* src/node_device/node_device_driver.c
(nodeDeviceVportCreateDelete): Likewise.
* src/util/cgroup.c (virCgroupSetValueStr): Likewise.
* src/util/pci.c (pciBindDeviceToStub, pciUnBindDeviceFromStub):
Likewise.
Based on a report from Jean-Baptiste Rouault.
---

> Alternatively, I only counted 16 existing users of virFileWriteStr; and
> this is an internal API.  We could easily rewrite all clients to always
> pass a third parameter, and change the signature of virFileWriteStr to
> require a mode_t argument.  Hmm; some of those clients are writing to
> kernel files that should always exist (/proc/sys/net/ipv4/ip_forward,
> for example), where it's tough to justify what we would pass as a mode_t
> argument.  So maybe pass mode==0 as a sentinel to require a pre-existing
> file

How does this look?  Admittedly, all existing uses were okay with a
mode parameter of 0; and I haven't yet seen your patch that would
use a non-zero mode, but this still makes more sense to me.

Oh, and VIR_FORCE_CLOSE preserves errno, so I was able to simplify
virFileWriteStr in the process.

 src/network/bridge_driver.c          |    8 ++++----
 src/node_device/node_device_driver.c |    2 +-
 src/util/cgroup.c                    |    2 +-
 src/util/pci.c                       |   16 ++++++++--------
 src/util/util.c                      |   13 ++++++++-----
 src/util/util.h                      |    3 ++-
 6 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
index 54890f9..62639e4 100644
--- a/src/network/bridge_driver.c
+++ b/src/network/bridge_driver.c
@@ -1024,7 +1024,7 @@ networkReloadIptablesRules(struct network_driver *driver)
 static int
 networkEnableIpForwarding(void)
 {
-    return virFileWriteStr("/proc/sys/net/ipv4/ip_forward", "1\n");
+    return virFileWriteStr("/proc/sys/net/ipv4/ip_forward", "1\n", 0);
 }

 #define SYSCTL_PATH "/proc/sys"
@@ -1045,7 +1045,7 @@ static int networkDisableIPV6(virNetworkObjPtr network)
         goto cleanup;
     }

-    if (virFileWriteStr(field, "1") < 0) {
+    if (virFileWriteStr(field, "1", 0) < 0) {
         virReportSystemError(errno,
                              _("cannot enable %s"), field);
         goto cleanup;
@@ -1057,7 +1057,7 @@ static int networkDisableIPV6(virNetworkObjPtr network)
         goto cleanup;
     }

-    if (virFileWriteStr(field, "0") < 0) {
+    if (virFileWriteStr(field, "0", 0) < 0) {
         virReportSystemError(errno,
                              _("cannot disable %s"), field);
         goto cleanup;
@@ -1069,7 +1069,7 @@ static int networkDisableIPV6(virNetworkObjPtr network)
         goto cleanup;
     }

-    if (virFileWriteStr(field, "1") < 0) {
+    if (virFileWriteStr(field, "1", 0) < 0) {
         virReportSystemError(errno,
                              _("cannot enable %s"), field);
         goto cleanup;
diff --git a/src/node_device/node_device_driver.c b/src/node_device/node_device_driver.c
index 448cfd3..a6c6042 100644
--- a/src/node_device/node_device_driver.c
+++ b/src/node_device/node_device_driver.c
@@ -454,7 +454,7 @@ nodeDeviceVportCreateDelete(const int parent_host,
         goto cleanup;
     }

-    if (virFileWriteStr(operation_path, vport_name) == -1) {
+    if (virFileWriteStr(operation_path, vport_name, 0) == -1) {
         virReportSystemError(errno,
                              _("Write of '%s' to '%s' during "
                                "vport create/delete failed"),
diff --git a/src/util/cgroup.c b/src/util/cgroup.c
index 2758a8f..3ba6325 100644
--- a/src/util/cgroup.c
+++ b/src/util/cgroup.c
@@ -288,7 +288,7 @@ static int virCgroupSetValueStr(virCgroupPtr group,
         return rc;

     VIR_DEBUG("Set value '%s' to '%s'", keypath, value);
-    rc = virFileWriteStr(keypath, value);
+    rc = virFileWriteStr(keypath, value, 0);
     if (rc < 0) {
         DEBUG("Failed to write value '%s': %m", value);
         rc = -errno;
diff --git a/src/util/pci.c b/src/util/pci.c
index d38cefa..095ad3f 100644
--- a/src/util/pci.c
+++ b/src/util/pci.c
@@ -849,7 +849,7 @@ pciBindDeviceToStub(pciDevice *dev, const char *driver)
      * bound by the stub.
      */
     pciDriverFile(path, sizeof(path), driver, "new_id");
-    if (virFileWriteStr(path, dev->id) < 0) {
+    if (virFileWriteStr(path, dev->id, 0) < 0) {
         virReportSystemError(errno,
                              _("Failed to add PCI device ID '%s' to %s"),
                              dev->id, driver);
@@ -862,7 +862,7 @@ pciBindDeviceToStub(pciDevice *dev, const char *driver)
      * your root filesystem.
      */
     pciDeviceFile(path, sizeof(path), dev->name, "driver/unbind");
-    if (virFileExists(path) && virFileWriteStr(path, dev->name) < 0) {
+    if (virFileExists(path) && virFileWriteStr(path, dev->name, 0) < 0) {
         virReportSystemError(errno,
                              _("Failed to unbind PCI device '%s'"), dev->name);
         return -1;
@@ -875,7 +875,7 @@ pciBindDeviceToStub(pciDevice *dev, const char *driver)
     if (!virFileLinkPointsTo(path, drvdir)) {
         /* Xen's pciback.ko wants you to use new_slot first */
         pciDriverFile(path, sizeof(path), driver, "new_slot");
-        if (virFileExists(path) && virFileWriteStr(path, dev->name) < 0) {
+        if (virFileExists(path) && virFileWriteStr(path, dev->name, 0) < 0) {
             virReportSystemError(errno,
                                  _("Failed to add slot for PCI device '%s' to %s"),
                                  dev->name, driver);
@@ -883,7 +883,7 @@ pciBindDeviceToStub(pciDevice *dev, const char *driver)
         }

         pciDriverFile(path, sizeof(path), driver, "bind");
-        if (virFileWriteStr(path, dev->name) < 0) {
+        if (virFileWriteStr(path, dev->name, 0) < 0) {
             virReportSystemError(errno,
                                  _("Failed to bind PCI device '%s' to %s"),
                                  dev->name, driver);
@@ -895,7 +895,7 @@ pciBindDeviceToStub(pciDevice *dev, const char *driver)
      * ID table so that 'drivers_probe' works below.
      */
     pciDriverFile(path, sizeof(path), driver, "remove_id");
-    if (virFileExists(path) && virFileWriteStr(path, dev->id) < 0) {
+    if (virFileExists(path) && virFileWriteStr(path, dev->id, 0) < 0) {
         virReportSystemError(errno,
                              _("Failed to remove PCI ID '%s' from %s"),
                              dev->id, driver);
@@ -936,7 +936,7 @@ pciUnBindDeviceFromStub(pciDevice *dev, const char *driver)
     pciDeviceFile(path, sizeof(path), dev->name, "driver");
     if (virFileExists(drvdir) && virFileLinkPointsTo(path, drvdir)) {
         pciDriverFile(path, sizeof(path), driver, "unbind");
-        if (virFileWriteStr(path, dev->name) < 0) {
+        if (virFileWriteStr(path, dev->name, 0) < 0) {
             virReportSystemError(errno,
                                  _("Failed to bind PCI device '%s' to %s"),
                                  dev->name, driver);
@@ -946,7 +946,7 @@ pciUnBindDeviceFromStub(pciDevice *dev, const char *driver)

     /* Xen's pciback.ko wants you to use remove_slot on the specific device */
     pciDriverFile(path, sizeof(path), driver, "remove_slot");
-    if (virFileExists(path) && virFileWriteStr(path, dev->name) < 0) {
+    if (virFileExists(path) && virFileWriteStr(path, dev->name, 0) < 0) {
         virReportSystemError(errno,
                              _("Failed to remove slot for PCI device '%s' to %s"),
                              dev->name, driver);
@@ -961,7 +961,7 @@ pciUnBindDeviceFromStub(pciDevice *dev, const char *driver)
      */
     pciDriverFile(path, sizeof(path), driver, "remove_id");
     if (!virFileExists(drvdir) || virFileExists(path)) {
-        if (virFileWriteStr(PCI_SYSFS "drivers_probe", dev->name) < 0) {
+        if (virFileWriteStr(PCI_SYSFS "drivers_probe", dev->name, 0) < 0) {
             virReportSystemError(errno,
                                  _("Failed to trigger a re-probe for PCI device '%s'"),
                                  dev->name);
diff --git a/src/util/util.c b/src/util/util.c
index f6050de..79ca5d3 100644
--- a/src/util/util.c
+++ b/src/util/util.c
@@ -1125,20 +1125,23 @@ int virFileReadAll(const char *path, int maxlen, char **buf)
     return len;
 }

-/* Truncate @path and write @str to it.
+/* Truncate @path and write @str to it.  If @mode is 0, ensure that
+   @path exists; otherwise, use @mode if @path must be created.
    Return 0 for success, nonzero for failure.
    Be careful to preserve any errno value upon failure. */
-int virFileWriteStr(const char *path, const char *str)
+int virFileWriteStr(const char *path, const char *str, mode_t mode)
 {
     int fd;

-    if ((fd = open(path, O_WRONLY|O_TRUNC)) == -1)
+    if (mode)
+        fd = open(path, O_WRONLY|O_TRUNC|O_CREAT, mode);
+    else
+        fd = open(path, O_WRONLY|O_TRUNC);
+    if (fd == -1)
         return -1;

     if (safewrite(fd, str, strlen(str)) < 0) {
-        int saved_errno = errno;
         VIR_FORCE_CLOSE(fd);
-        errno = saved_errno;
         return -1;
     }

diff --git a/src/util/util.h b/src/util/util.h
index deaf8bb..ef4fc13 100644
--- a/src/util/util.h
+++ b/src/util/util.h
@@ -97,7 +97,8 @@ int virFileReadLimFD(int fd, int maxlen, char **buf) ATTRIBUTE_RETURN_CHECK;

 int virFileReadAll(const char *path, int maxlen, char **buf) ATTRIBUTE_RETURN_CHECK;

-int virFileWriteStr(const char *path, const char *str) ATTRIBUTE_RETURN_CHECK;
+int virFileWriteStr(const char *path, const char *str, mode_t mode)
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_RETURN_CHECK;

 int virFileMatchesNameSuffix(const char *file,
                              const char *name,
-- 
1.7.3.2


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