[Qemu-devel] [PATCH] Add QMP fsfreeze support

[Jes . Sorensen]

From: Jes Sorensen <address@hidden>

This patch adds the following QMP commands:
qga-guest-fsfreeze:
 - Freezes all local file systems in the guest. Command will return
   the number of file systems that were frozen.
qga-guest-fsthaw:
 - Thaws all local file systems in the guest. Command will return
   the number of file systems that were thawed.

Signed-off-by: Jes Sorensen <address@hidden>
---
 qapi-schema.json           |   24 ++++++
 qga/guest-agent-commands.c |  177 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 201 insertions(+), 0 deletions(-)

diff --git a/qapi-schema.json b/qapi-schema.json
index e2f209d..2c86cec 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1562,6 +1562,30 @@
 { 'option': 'blockdev', 'data': 'BlockdevConfig', 'implicit': 'id' }
 
 ##
+# @guest-fsfreeze:
+#
+# json gibberish for guest-fsfreeze command
+#
+# Returns: Number of file systems frozen
+#
+# Since: 0.15.0
+##
+{ 'command': 'guest-fsfreeze',
+  'returns': 'int' }
+
+##
+# @guest-fsthaw:
+#
+# json gibberish for guest-fsthaw command
+#
+# Returns: Number of file systems thawed
+#
+# Since: 0.15.0
+##
+{ 'command': 'guest-fsthaw',
+  'returns': 'int' }
+
+##
 # @VncConfig:
 #
 # Configuration options for the built-in VNC server.
diff --git a/qga/guest-agent-commands.c b/qga/guest-agent-commands.c
index 843ef36..4bc2c57 100644
--- a/qga/guest-agent-commands.c
+++ b/qga/guest-agent-commands.c
@@ -11,6 +11,10 @@
  */
 
 #include <glib.h>
+#include <mntent.h>
+#include <sys/types.h>
+#include <sys/ioctl.h>
+#include <linux/fs.h>
 #include "guest-agent.h"
 
 static bool enable_syslog = true;
@@ -262,6 +266,179 @@ struct GuestFileSeek *qga_guest_file_seek(int64_t 
filehandle, int64_t offset,
     return seek_data;
 }
 
+/*
+ * Walk the mount table and build a list of local file systems
+ */
+struct direntry {
+    char *dirname;
+    char *devtype;
+    struct direntry *next;
+};
+
+struct va_freezestate {
+    struct direntry *mount_list;
+    int status;
+};
+
+/*
+ * This should be in a header file, but we have none :(
+ */
+enum va_fsfreeze_status {
+    FREEZE_ERROR = -1,
+    FREEZE_THAWED = 0,
+    FREEZE_INPROGRESS = 1,
+    FREEZE_FROZEN = 2,
+    FREEZE_THAWINPROGRESS = 3,
+};
+
+static struct va_freezestate freezestate;
+
+static int build_mount_list(void)
+{
+    struct mntent *mnt;
+    struct direntry *entry;
+    struct direntry *next;
+    char const *mtab = MOUNTED;
+    FILE *fp;
+
+    fp = setmntent(mtab, "r");
+    if (!fp) {
+        fprintf(stderr, "unable to read mtab\n");
+        goto fail;
+    }
+
+    while ((mnt = getmntent(fp))) {
+        /*
+         * An entry which device name doesn't start with a '/' is
+         * either a dummy file system or a network file system.
+         * Add special handling for smbfs and cifs as is done by
+         * coreutils as well.
+         */
+        if ((mnt->mnt_fsname[0] != '/') ||
+            (strcmp(mnt->mnt_type, "smbfs") == 0) ||
+            (strcmp(mnt->mnt_type, "cifs") == 0)) {
+            continue;
+        }
+
+        entry = qemu_malloc(sizeof(struct direntry));
+        entry->dirname = qemu_strdup(mnt->mnt_dir);
+        entry->devtype = qemu_strdup(mnt->mnt_type);
+        entry->next = freezestate.mount_list;
+
+        freezestate.mount_list = entry;
+    }
+
+    endmntent(fp);
+
+    return 0;
+ 
+fail:
+    while(freezestate.mount_list) {
+        next = freezestate.mount_list->next;
+        qemu_free(freezestate.mount_list->dirname);
+        qemu_free(freezestate.mount_list->devtype);
+        qemu_free(freezestate.mount_list);
+        freezestate.mount_list = next;
+    }
+
+    return -1;
+}
+
+/*
+ * qga_guest_fsfreeze(): Walk list of mounted file systems in the
+ *   guest, and freeze the ones which are real local file systems.
+ * return values: Number of file systems frozen, -1 on error.
+ */
+int64_t qga_guest_fsfreeze(Error **err)
+{
+    struct direntry *entry;
+    int fd, i = 0;
+    int64_t ret;
+    SLOG("va_fsfreeze()");
+
+    if (freezestate.status != FREEZE_THAWED) {
+        ret = 0;
+        goto out;
+    }
+
+    ret = build_mount_list();
+    if (ret < 0) {
+        goto out;
+    }
+
+    freezestate.status = FREEZE_INPROGRESS;
+
+    entry = freezestate.mount_list;
+    while(entry) {
+        fd = qemu_open(entry->dirname, O_RDONLY);
+        if (fd == -1) {
+            ret = errno;
+            goto error;
+        }
+        ret = ioctl(fd, FIFREEZE);
+        close(fd);
+        if (ret < 0 && ret != EOPNOTSUPP) {
+            goto error;
+        }
+
+        entry = entry->next;
+        i++;
+    }
+
+    freezestate.status = FREEZE_FROZEN;
+    ret = i;
+out:
+    return ret;
+error:
+    if (i > 0) {
+        freezestate.status = FREEZE_ERROR;
+    }
+    goto out;
+}
+
+/*
+ * qga_guest_fsthaw(): Walk list of frozen file systems in the guest, and
+ *   thaw them.
+ * return values: Number of file systems thawed on success, -1 on error.
+ */
+int64_t qga_guest_fsthaw(Error **err)
+{
+    struct direntry *entry;
+    int fd, i = 0;
+    int64_t ret;
+    SLOG("va_fsthaw()");
+
+    if (freezestate.status != FREEZE_FROZEN) {
+        ret = 0;
+        goto out;
+    }
+
+    while((entry = freezestate.mount_list)) {
+        fd = qemu_open(entry->dirname, O_RDONLY);
+        if (fd == -1) {
+            ret = -1;
+            goto out;
+        }
+        ret = ioctl(fd, FITHAW);
+        close(fd);
+        if (ret < 0 && ret != EOPNOTSUPP) {
+            ret = -1;
+            goto out;
+        }
+
+        freezestate.mount_list = entry->next;
+        qemu_free(entry->dirname);
+        qemu_free(entry->devtype);
+        qemu_free(entry);
+        i++;
+    }
+
+    freezestate.status = FREEZE_THAWED;
+    ret = i;
+out:
+    return ret;
+}
+
 void qga_guest_file_close(int64_t filehandle, Error **err)
 {
     FILE *fh = guest_file_handle_find(filehandle);
-- 
1.7.4.4