[libvirt] [PATCH] Unmount existing filesystems under user specified mounts in LXC
Daniel P. Berrange
berrange at redhat.com
Mon Apr 8 15:12:11 UTC 2013
From: "Daniel P. Berrange" <berrange at redhat.com>
If the user requests a mount for /run, this may hide any existing
mounts that are lower down in /run. The result is that the
container still sees the mounts in /proc/mounts, but cannot
access them
sh-4.2# df
df: '/run/user/501/gvfs': No such file or directory
df: '/run/media/berrange/LIVE': No such file or directory
df: '/run/media/berrange/SecureDiskA1': No such file or directory
df: '/run/libvirt/lxc/sandbox': No such file or directory
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/vg_t500wlan-lv_root 151476396 135390200 8384900 95% /
tmpfs 1970888 3204 1967684 1% /run
/dev/sda1 194241 155940 28061 85% /boot
devfs 64 0 64 0% /dev
tmpfs 64 0 64 0% /sys/fs/cgroup
tmpfs 1970888 1200 1969688 1% /etc/libvirt-sandbox/scratch
Before mounting any filesystem at a particular location, we
must recursively unmount anything at or below the target mount
point
Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
---
src/lxc/lxc_container.c | 218 ++++++++++++++++++++++++------------------------
1 file changed, 111 insertions(+), 107 deletions(-)
diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
index e59bfdf..30738bb 100644
--- a/src/lxc/lxc_container.c
+++ b/src/lxc/lxc_container.c
@@ -409,6 +409,113 @@ static int lxcContainerChildMountSort(const void *a, const void *b)
# define MS_SLAVE (1<<19)
#endif
+static int lxcContainerGetSubtree(const char *prefix,
+ char ***mountsret,
+ size_t *nmountsret)
+{
+ FILE *procmnt;
+ struct mntent mntent;
+ char mntbuf[1024];
+ int ret = -1;
+ char **mounts = NULL;
+ size_t nmounts = 0;
+
+ VIR_DEBUG("prefix=%s", prefix);
+
+ *mountsret = NULL;
+ *nmountsret = 0;
+
+ if (!(procmnt = setmntent("/proc/mounts", "r"))) {
+ virReportSystemError(errno, "%s",
+ _("Failed to read /proc/mounts"));
+ return -1;
+ }
+
+ while (getmntent_r(procmnt, &mntent, mntbuf, sizeof(mntbuf)) != NULL) {
+ VIR_DEBUG("Got %s", mntent.mnt_dir);
+ if (!STRPREFIX(mntent.mnt_dir, prefix))
+ continue;
+
+ if (VIR_REALLOC_N(mounts, nmounts+1) < 0) {
+ virReportOOMError();
+ goto cleanup;
+ }
+ if (!(mounts[nmounts] = strdup(mntent.mnt_dir))) {
+ virReportOOMError();
+ goto cleanup;
+ }
+ nmounts++;
+ VIR_DEBUG("Grabbed %s", mntent.mnt_dir);
+ }
+
+ if (mounts)
+ qsort(mounts, nmounts, sizeof(mounts[0]),
+ lxcContainerChildMountSort);
+
+ ret = 0;
+cleanup:
+ *mountsret = mounts;
+ *nmountsret = nmounts;
+ endmntent(procmnt);
+ return ret;
+}
+
+static int lxcContainerUnmountSubtree(const char *prefix,
+ bool isOldRootFS)
+{
+ char **mounts = NULL;
+ size_t nmounts = 0;
+ size_t i;
+ int saveErrno;
+ const char *failedUmount = NULL;
+ int ret = -1;
+
+ VIR_DEBUG("Unmount subtreee from %s", prefix);
+
+ if (lxcContainerGetSubtree(prefix, &mounts, &nmounts) < 0)
+ goto cleanup;
+ for (i = 0 ; i < nmounts ; i++) {
+ VIR_DEBUG("Umount %s", mounts[i]);
+ if (umount(mounts[i]) < 0) {
+ char ebuf[1024];
+ failedUmount = mounts[i];
+ saveErrno = errno;
+ VIR_WARN("Failed to unmount '%s', trying to detach subtree '%s': %s",
+ failedUmount, mounts[nmounts-1],
+ virStrerror(errno, ebuf, sizeof(ebuf)));
+ break;
+ }
+ }
+
+ if (failedUmount) {
+ /* This detaches the subtree */
+ if (umount2(mounts[nmounts-1], MNT_DETACH) < 0) {
+ virReportSystemError(saveErrno,
+ _("Failed to unmount '%s' and could not detach subtree '%s'"),
+ failedUmount, mounts[nmounts-1]);
+ goto cleanup;
+ }
+ /* This unmounts the tmpfs on which the old root filesystem was hosted */
+ if (isOldRootFS &&
+ umount(mounts[nmounts-1]) < 0) {
+ virReportSystemError(saveErrno,
+ _("Failed to unmount '%s' and could not unmount old root '%s'"),
+ failedUmount, mounts[nmounts-1]);
+ goto cleanup;
+ }
+ }
+
+ ret = 0;
+
+cleanup:
+ for (i = 0 ; i < nmounts ; i++)
+ VIR_FREE(mounts[i]);
+ VIR_FREE(mounts);
+
+ return ret;
+}
+
+
static int lxcContainerPrepareRoot(virDomainDefPtr def,
virDomainFSDefPtr root)
{
@@ -1254,6 +1361,10 @@ static int lxcContainerMountAllFS(virDomainDefPtr vmDef,
STREQ(vmDef->fss[i]->dst, "/"))
continue;
+ if (lxcContainerUnmountSubtree(vmDef->fss[i]->dst,
+ false) < 0)
+ return -1;
+
if (lxcContainerMountFS(vmDef->fss[i], dstprefix, sec_mount_options) < 0)
return -1;
}
@@ -1624,113 +1735,6 @@ static int lxcContainerSetupAllHostdevs(virDomainDefPtr vmDef,
}
-static int lxcContainerGetSubtree(const char *prefix,
- char ***mountsret,
- size_t *nmountsret)
-{
- FILE *procmnt;
- struct mntent mntent;
- char mntbuf[1024];
- int ret = -1;
- char **mounts = NULL;
- size_t nmounts = 0;
-
- VIR_DEBUG("prefix=%s", prefix);
-
- *mountsret = NULL;
- *nmountsret = 0;
-
- if (!(procmnt = setmntent("/proc/mounts", "r"))) {
- virReportSystemError(errno, "%s",
- _("Failed to read /proc/mounts"));
- return -1;
- }
-
- while (getmntent_r(procmnt, &mntent, mntbuf, sizeof(mntbuf)) != NULL) {
- VIR_DEBUG("Got %s", mntent.mnt_dir);
- if (!STRPREFIX(mntent.mnt_dir, prefix))
- continue;
-
- if (VIR_REALLOC_N(mounts, nmounts+1) < 0) {
- virReportOOMError();
- goto cleanup;
- }
- if (!(mounts[nmounts] = strdup(mntent.mnt_dir))) {
- virReportOOMError();
- goto cleanup;
- }
- nmounts++;
- VIR_DEBUG("Grabbed %s", mntent.mnt_dir);
- }
-
- if (mounts)
- qsort(mounts, nmounts, sizeof(mounts[0]),
- lxcContainerChildMountSort);
-
- ret = 0;
-cleanup:
- *mountsret = mounts;
- *nmountsret = nmounts;
- endmntent(procmnt);
- return ret;
-}
-
-static int lxcContainerUnmountSubtree(const char *prefix,
- bool isOldRootFS)
-{
- char **mounts = NULL;
- size_t nmounts = 0;
- size_t i;
- int saveErrno;
- const char *failedUmount = NULL;
- int ret = -1;
-
- VIR_DEBUG("Unmount subtreee from %s", prefix);
-
- if (lxcContainerGetSubtree(prefix, &mounts, &nmounts) < 0)
- goto cleanup;
- for (i = 0 ; i < nmounts ; i++) {
- VIR_DEBUG("Umount %s", mounts[i]);
- if (umount(mounts[i]) < 0) {
- char ebuf[1024];
- failedUmount = mounts[i];
- saveErrno = errno;
- VIR_WARN("Failed to unmount '%s', trying to detach subtree '%s': %s",
- failedUmount, mounts[nmounts-1],
- virStrerror(errno, ebuf, sizeof(ebuf)));
- break;
- }
- }
-
- if (failedUmount) {
- /* This detaches the subtree */
- if (umount2(mounts[nmounts-1], MNT_DETACH) < 0) {
- virReportSystemError(saveErrno,
- _("Failed to unmount '%s' and could not detach subtree '%s'"),
- failedUmount, mounts[nmounts-1]);
- goto cleanup;
- }
- /* This unmounts the tmpfs on which the old root filesystem was hosted */
- if (isOldRootFS &&
- umount(mounts[nmounts-1]) < 0) {
- virReportSystemError(saveErrno,
- _("Failed to unmount '%s' and could not unmount old root '%s'"),
- failedUmount, mounts[nmounts-1]);
- goto cleanup;
- }
- }
-
- ret = 0;
-
-cleanup:
- for (i = 0 ; i < nmounts ; i++)
- VIR_FREE(mounts[i]);
- VIR_FREE(mounts);
-
- return ret;
-}
-
-
struct lxcContainerCGroup {
const char *dir;
const char *linkDest;
--
1.8.1.4
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