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Re: [libvirt] [PATCH] LXC: create directory /dev/shm automatically



(2013/01/28 19:36), Daniel P. Berrange wrote:
On Mon, Jan 28, 2013 at 02:37:11PM +0800, Gao feng wrote:
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.

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

Signed-off-by: Gao feng <gaofeng cn fujitsu com>
---
  src/lxc/lxc_container.c | 7 +++++++
  1 file changed, 7 insertions(+)

diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
index 497539c..5150564 100644
--- a/src/lxc/lxc_container.c
+++ b/src/lxc/lxc_container.c
@@ -586,6 +586,13 @@ 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;

I we probably want to mount a separate tmpfs on /dev/shm really, so we can
do resource limits on /dev and /dev/shm separately.

I agree.
BTW, if the user wants to tune limit of /dev/shm size, he need to add

<filesystem type='ram'>
  <source usage='XXXXX'/>
  <target dir='/dev/shm'/>
</filesystem>

?

How do you think suitable limit for default should be ?
half of memory limit of a container ?


THanks,
-Kame



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