[PATCH v2] LXC: create directory /dev/shm automatically

[Gao feng <gaofeng@xxxxxxxxxxxxxx>]

Now we mount /dev as tmpfs and haven't created directory
/dev/shm,so the glibc api such as shm_open/sem_open will
create files under dir /dev.(since /dev is mounted as tmpfs)

Through these api still useable in container,but this cause
directory /dev looks a little chaos.

We already have filesystem type "ram",if user want to limit
the memory usage of /dev/shm,he should configure the XML,so
we only need to create directroy /dev/shm.If user configure
the filesystem type on /dev/shm, we will mount it on /dev/shm
then.

This patch create directory /dev/shm automatically,the files
created by shm_open/sem_open will stay in this directroy.

This patch also enlarge the size of directroy /dev to the
half of container's memory,64k may be too small to contain
POSIX shared memory and named semphore.

Signed-off-by: Gao feng <gaofeng@xxxxxxxxxxxxxx>
---
 src/lxc/lxc_container.c | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
index 497539c..eba3e68 100644
--- a/src/lxc/lxc_container.c
+++ b/src/lxc/lxc_container.c
@@ -504,7 +504,8 @@ err:
 
 
 static int lxcContainerMountBasicFS(bool pivotRoot,
-                                    char *sec_mount_options)
+                                    char *sec_mount_options,
+                                    virDomainDefPtr vmDef)
 {
     const struct {
         const char *src;
@@ -567,12 +568,22 @@ static int lxcContainerMountBasicFS(bool pivotRoot,
 
     if (pivotRoot) {
         /*
-         * tmpfs is limited to 64kb, since we only have device nodes in there
-         * and don't want to DOS the entire OS RAM usage
+         * tmpfs is limited to half of container's memory,
+         * since we not only have device nodes in there,we
+         * may have POSIX shared memory object and named
+         * semphore in there too.
          */
 
-        ignore_value(virAsprintf(&opts,
-                                 "mode=755,size=65536%s", sec_mount_options));
+        if (vmDef->mem.max_balloon != VIR_DOMAIN_MEMORY_PARAM_UNLIMITED) {
+            unsigned long long size = 0;
+            size = vmDef->mem.max_balloon << 9;
+            ignore_value(virAsprintf(&opts,
+                         "mode=755,size=%llu%s", size, sec_mount_options));
+        } else {
+            ignore_value(virAsprintf(&opts,
+                                 "mode=755,%s", sec_mount_options));
+        }
+
         if (!opts) {
             virReportOOMError();
             goto cleanup;
@@ -586,6 +597,13 @@ static int lxcContainerMountBasicFS(bool pivotRoot,
                                  "devfs", "/dev", "tmpfs", opts);
             goto cleanup;
         }
+
+        VIR_DEBUG("create directory /dev/shm for POSIX shared memory and named semphore");
+        if (virFileMakePath("/dev/shm") < 0) {
+            virReportSystemError(errno, "%s",
+                                 _("Failed to mkdir /dev/shm"));
+            goto cleanup;
+        }
     }
 
     rc = 0;
@@ -1947,7 +1965,7 @@ static int lxcContainerSetupPivotRoot(virDomainDefPtr vmDef,
         goto cleanup;
 
     /* Mounts the core /proc, /sys, etc filesystems */
-    if (lxcContainerMountBasicFS(true, sec_mount_options) < 0)
+    if (lxcContainerMountBasicFS(true, sec_mount_options, vmDef) < 0)
         goto cleanup;
 
     /* Mounts /proc/meminfo etc sysinfo */
@@ -2055,7 +2073,7 @@ static int lxcContainerSetupExtraMounts(virDomainDefPtr vmDef,
         goto cleanup;
 
     /* Mounts the core /proc, /sys, etc filesystems */
-    if (lxcContainerMountBasicFS(false, sec_mount_options) < 0)
+    if (lxcContainerMountBasicFS(false, sec_mount_options, vmDef) < 0)
         goto cleanup;
 
     /* Mounts /proc/meminfo etc sysinfo */
-- 
1.7.11.7

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