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[Libguestfs] [PATCH v3] Allow 9p filesystems to be listed and mounted (RHBZ#714981).



On Wed, Jun 22, 2011 at 03:04:02PM +0100, Daniel P. Berrange wrote:
> Is it possible to make 'options' the 3rd parameter, and optional,
> so you don't need todo
> 
>    ><fs> mount-9p "" org.kernel.other /tmp/
> 
> Which is the common case.

It certainly is.  Try the attached (first patch is identical to the
earlier version).

The syntax in guestfish is now:

  mount-9p org.kernel.other /tmp

or:

  mount-9p org.kernel.other /tmp options:ro

or you can quote the optional arg, but note that quotes have to go
around the whole string, eg:

  mount-9p org.kernel.other /tmp "options:ro"

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
Fedora now supports 80 OCaml packages (the OPEN alternative to F#)
http://cocan.org/getting_started_with_ocaml_on_red_hat_and_fedora
>From 5f10c3350338bbca735a74db26f98da968957bd9 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones redhat com>
Date: Wed, 22 Jun 2011 10:13:23 +0100
Subject: [PATCH 1/2] New API: list-9p lists 9p filesystem mount tags
 (RHBZ#714981).

---
 daemon/9p.c                    |  170 ++++++++++++++++++++++++++++++++++++++++
 daemon/Makefile.am             |    1 +
 generator/generator_actions.ml |    7 ++
 po/POTFILES.in                 |    1 +
 src/MAX_PROC_NR                |    2 +-
 5 files changed, 180 insertions(+), 1 deletions(-)
 create mode 100644 daemon/9p.c

diff --git a/daemon/9p.c b/daemon/9p.c
new file mode 100644
index 0000000..bc95803
--- /dev/null
+++ b/daemon/9p.c
@@ -0,0 +1,170 @@
+/* libguestfs - the guestfsd daemon
+ * Copyright (C) 2011 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <limits.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <dirent.h>
+#include <fcntl.h>
+
+#include "daemon.h"
+#include "actions.h"
+
+#define BUS_PATH "/sys/bus/virtio/drivers/9pnet_virtio"
+
+static char *read_whole_file (const char *filename);
+
+/* https://bugzilla.redhat.com/show_bug.cgi?id=714981#c1 */
+char **
+do_list_9p (void)
+{
+  char **r = NULL;
+  int size = 0, alloc = 0;
+
+  DIR *dir;
+  int err = 0;
+
+  dir = opendir (BUS_PATH);
+  if (!dir) {
+    perror ("opendir: " BUS_PATH);
+    if (errno != ENOENT)
+      return NULL;
+
+    /* If this directory doesn't exist, it probably means that
+     * the virtio driver isn't loaded.  Don't return an error
+     * in this case, but return an empty list.
+     */
+    if (add_string (&r, &size, &alloc, NULL) == -1)
+      return NULL;
+
+    return r;
+  }
+
+  while (1) {
+    errno = 0;
+    struct dirent *d = readdir (dir);
+    if (d == NULL) break;
+
+    if (STRPREFIX (d->d_name, "virtio")) {
+      char mount_tag_path[256];
+      snprintf (mount_tag_path, sizeof mount_tag_path,
+                BUS_PATH "/%s/mount_tag", d->d_name);
+
+      /* A bit unclear, but it looks like the virtio transport allows
+       * the mount tag length to be unlimited (or up to 65536 bytes).
+       * See: linux/include/linux/virtio_9p.h
+       */
+      char *mount_tag = read_whole_file (mount_tag_path);
+      if (mount_tag == 0)
+        continue;
+
+      if (add_string (&r, &size, &alloc, mount_tag) == -1) {
+        free (mount_tag);
+        free_stringslen (r, size);
+        closedir (dir);
+        return NULL;
+      }
+
+      free (mount_tag);
+    }
+  }
+
+  /* Check readdir didn't fail */
+  if (errno != 0) {
+    reply_with_perror ("readdir: /sys/block");
+    free_stringslen (r, size);
+    closedir (dir);
+    return NULL;
+  }
+
+  /* Close the directory handle */
+  if (closedir (dir) == -1) {
+    reply_with_perror ("closedir: /sys/block");
+    free_stringslen (r, size);
+    return NULL;
+  }
+
+  /* Sort the tags.  Note that r might be NULL if there are no tags. */
+  if (r != NULL)
+    sort_strings (r, size);
+
+  /* NULL terminate the list */
+  if (add_string (&r, &size, &alloc, NULL) == -1)
+    return NULL;
+
+  return r;
+}
+
+/* Read whole file into dynamically allocated array.  If there is an
+ * error, DON'T call reply_with_perror, just return NULL.  Returns a
+ * \0-terminated string.
+ */
+static char *
+read_whole_file (const char *filename)
+{
+  char *r = NULL;
+  size_t alloc = 0, size = 0;
+  int fd;
+
+  fd = open (filename, O_RDONLY);
+  if (fd == -1) {
+    perror (filename);
+    return NULL;
+  }
+
+  while (1) {
+    alloc += 256;
+    char *r2 = realloc (r, alloc);
+    if (r2 == NULL) {
+      perror ("realloc");
+      free (r);
+      return NULL;
+    }
+    r = r2;
+
+    /* The '- 1' in the size calculation ensures there is space below
+     * to add \0 to the end of the input.
+     */
+    ssize_t n = read (fd, r + size, alloc - size - 1);
+    if (n == -1) {
+      perror (filename);
+      free (r);
+      return NULL;
+    }
+    if (n == 0)
+      break;
+    size += n;
+  }
+
+  if (close (fd) == -1) {
+    perror (filename);
+    free (r);
+    return NULL;
+  }
+
+  r[size] = '\0';
+
+  return r;
+}
diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index 8fb070f..78049c9 100644
--- a/daemon/Makefile.am
+++ b/daemon/Makefile.am
@@ -88,6 +88,7 @@ errnostring.h: $(libsrcdir)/errnostring.h
 
 noinst_PROGRAMS = guestfsd
 guestfsd_SOURCES = \
+	9p.c \
 	actions.h \
 	available.c \
 	augeas.c \
diff --git a/generator/generator_actions.ml b/generator/generator_actions.ml
index 74b6515..634ceeb 100644
--- a/generator/generator_actions.ml
+++ b/generator/generator_actions.ml
@@ -5960,6 +5960,13 @@ This returns true iff the device exists and contains all zero bytes.
 
 Note that for large devices this can take a long time to run.");
 
+  ("list_9p", (RStringList "mounttags", [], []), 285, [],
+   [],
+   "list 9p filesystems",
+   "\
+List all 9p filesystems attached to the guest.  A list of
+mount tags is returned.");
+
 ]
 
 let all_functions = non_daemon_functions @ daemon_functions
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 7c0df52..da47c91 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -1,6 +1,7 @@
 cat/virt-cat.c
 cat/virt-filesystems.c
 cat/virt-ls.c
+daemon/9p.c
 daemon/augeas.c
 daemon/available.c
 daemon/base64.c
diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
index c9716b7..6cf4452 100644
--- a/src/MAX_PROC_NR
+++ b/src/MAX_PROC_NR
@@ -1 +1 @@
-284
+285
-- 
1.7.5.2

>From 14bb3b5ae75f41af05ca6d26ebbb5e85aacf2e20 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones redhat com>
Date: Wed, 22 Jun 2011 13:55:14 +0100
Subject: [PATCH 2/2] New API: mount-9p lets you mount 9p filesystems
 (RHBZ#714981).

The updated patch makes 'options' into an optional parameter.
---
 daemon/9p.c                    |   57 ++++++++++++++++++++++++++++++++++++++++
 generator/generator_actions.ml |   11 +++++++
 src/MAX_PROC_NR                |    2 +-
 3 files changed, 69 insertions(+), 1 deletions(-)

diff --git a/daemon/9p.c b/daemon/9p.c
index bc95803..9e89e08 100644
--- a/daemon/9p.c
+++ b/daemon/9p.c
@@ -168,3 +168,60 @@ read_whole_file (const char *filename)
 
   return r;
 }
+
+/* Takes optional arguments, consult optargs_bitmask. */
+int
+do_mount_9p (const char *mount_tag, const char *mountpoint, const char *options)
+{
+  char *mp = NULL, *opts = NULL, *err = NULL;
+  struct stat statbuf;
+  int r = -1;
+
+  ABS_PATH (mountpoint, , return -1);
+
+  mp = sysroot_path (mountpoint);
+  if (!mp) {
+    reply_with_perror ("malloc");
+    goto out;
+  }
+
+  /* Check the mountpoint exists and is a directory. */
+  if (stat (mp, &statbuf) == -1) {
+    reply_with_perror ("%s", mountpoint);
+    goto out;
+  }
+  if (!S_ISDIR (statbuf.st_mode)) {
+    reply_with_perror ("%s: mount point is not a directory", mountpoint);
+    goto out;
+  }
+
+  /* Add trans=virtio to the options. */
+  if ((optargs_bitmask & GUESTFS_MOUNT_9P_OPTIONS_BITMASK) &&
+      STRNEQ (options, "")) {
+    if (asprintf (&opts, "trans=virtio,%s", options) == -1) {
+      reply_with_perror ("asprintf");
+      goto out;
+    }
+  }
+  else {
+    opts = strdup ("trans=virtio");
+    if (opts == NULL) {
+      reply_with_perror ("strdup");
+      goto out;
+    }
+  }
+
+  r = command (NULL, &err,
+               "mount", "-o", opts, "-t", "9p", mount_tag, mp, NULL);
+  if (r == -1) {
+    reply_with_error ("%s on %s: %s", mount_tag, mountpoint, err);
+    goto out;
+  }
+
+  r = 0;
+ out:
+  free (err);
+  free (opts);
+  free (mp);
+  return r;
+}
diff --git a/generator/generator_actions.ml b/generator/generator_actions.ml
index 634ceeb..9130034 100644
--- a/generator/generator_actions.ml
+++ b/generator/generator_actions.ml
@@ -5967,6 +5967,17 @@ Note that for large devices this can take a long time to run.");
 List all 9p filesystems attached to the guest.  A list of
 mount tags is returned.");
 
+  ("mount_9p", (RErr, [String "mounttag"; String "mountpoint"], [String "options"]), 286, [],
+   [],
+   "mount 9p filesystem",
+   "\
+Mount the virtio-9p filesystem with the tag C<mounttag> on the
+directory C<mountpoint>.
+
+If required, C<trans=virtio> will be automatically added to the options.
+Any other options required can be passed in the optional C<options>
+parameter.");
+
 ]
 
 let all_functions = non_daemon_functions @ daemon_functions
diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
index 6cf4452..c20f657 100644
--- a/src/MAX_PROC_NR
+++ b/src/MAX_PROC_NR
@@ -1 +1 @@
-285
+286
-- 
1.7.5.2


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