This makes the following changes to the rootfs pinning mechanism:
- Contrary to a recent change, the file will not be deleted
immediately after creation. This should make NFS happy.
- To reduce nuissance for administrators, make the file hidden by
default.
- Delete the file at container shutdown. (i.e. clean up after oneself)
- Because the file is now deleted, and a rootfs could be shared
between containers, the filename now encodes the pid of the
lxc-start process, so that the rw-hold on the filesystem will only
be removed once the last container exits.
Signed-off-by: Christian Seiler <christ...@iwakd.de>
---
src/lxc/conf.c | 24 +++++++++++++++---------
src/lxc/conf.h | 2 +-
src/lxc/start.c | 10 +++++++++-
src/lxc/start.h | 1 +
4 files changed, 26 insertions(+), 11 deletions(-)
diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index ecbcf41..4cd9462 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -695,15 +695,18 @@ static int mount_rootfs_block(const char *rootfs, const
char *target)
/*
* pin_rootfs
- * if rootfs is a directory, then open ${rootfs}/lxc.hold for writing for
- * the duration of the container run, to prevent the container from marking
- * the underlying fs readonly on shutdown. unlink the file immediately so
- * no name pollution is happens
+ * if rootfs is a directory, then open ${rootfs}/.lxc-hold-$pid for writing
+ * for the duration of the container run, to prevent the container from
+ * marking the underlying fs readonly on shutdown. $pid is the pid of
+ * lxc-start. At shutdown the hold file will be removed again. The pid is
+ * encoded in the filename, so that if multiple containers use the same
+ * root filesystem, a hold will be kept open until the last container is
+ * stopped.
* return -1 on error.
* return -2 if nothing needed to be pinned.
* return an open fd (>=0) if we pinned it.
*/
-int pin_rootfs(const char *rootfs)
+int pin_rootfs(const char *rootfs, char **filename_ptr)
{
char absrootfs[MAXPATHLEN];
char absrootfspin[MAXPATHLEN];
@@ -725,16 +728,19 @@ int pin_rootfs(const char *rootfs)
if (!S_ISDIR(s.st_mode))
return -2;
- ret = snprintf(absrootfspin, MAXPATHLEN, "%s/lxc.hold", absrootfs);
+ ret = snprintf(absrootfspin, MAXPATHLEN, "%s/.lxc-hold-%lu", absrootfs,
(unsigned long)getpid());
if (ret >= MAXPATHLEN)
return -1;
+ if (filename_ptr) {
+ *filename_ptr = strdup(absrootfspin);
+ if (!*filename_ptr)
+ return -1;
+ }
+
process_lock();
fd = open(absrootfspin, O_CREAT | O_RDWR, S_IWUSR|S_IRUSR);
process_unlock();
- if (fd < 0)
- return fd;
- (void)unlink(absrootfspin);
return fd;
}
diff --git a/src/lxc/conf.h b/src/lxc/conf.h
index 84acce8..e3a962a 100644
--- a/src/lxc/conf.h
+++ b/src/lxc/conf.h
@@ -331,7 +331,7 @@ extern int detect_shared_rootfs(void);
extern struct lxc_conf *lxc_conf_init(void);
extern void lxc_conf_free(struct lxc_conf *conf);
-extern int pin_rootfs(const char *rootfs);
+extern int pin_rootfs(const char *rootfs, char **filename_ptr);
extern int lxc_create_network(struct lxc_handler *handler);
extern void lxc_delete_network(struct lxc_handler *handler);
diff --git a/src/lxc/start.c b/src/lxc/start.c
index 7538403..26c71c4 100644
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -386,6 +386,14 @@ static void lxc_fini(const char *name, struct lxc_handler
*handler)
if (run_lxc_hooks(name, "post-stop", handler->conf, handler->lxcpath,
NULL))
ERROR("failed to run post-stop hooks for container '%s'.",
name);
+ /* remove rootfs pin file after we shutdown this
+ * container
+ */
+ if (handler->pin_filename) {
+ unlink(handler->pin_filename);
+ free(handler->pin_filename);
+ }
+
/* reset mask set by setup_signal_fd */
if (sigprocmask(SIG_SETMASK, &handler->oldmask, NULL))
WARN("failed to restore sigprocmask");
@@ -708,7 +716,7 @@ int lxc_spawn(struct lxc_handler *handler)
* marking it readonly.
*/
- handler->pinfd = pin_rootfs(handler->conf->rootfs.path);
+ handler->pinfd = pin_rootfs(handler->conf->rootfs.path,
&handler->pin_filename);
if (handler->pinfd == -1)
INFO("failed to pin the container's rootfs");
diff --git a/src/lxc/start.h b/src/lxc/start.h
index c35c5c4..345b4e0 100644
--- a/src/lxc/start.h
+++ b/src/lxc/start.h
@@ -50,6 +50,7 @@ struct lxc_handler {
struct lxc_operations *ops;
void *data;
int sv[2];
+ char *pin_filename;
int pinfd;
const char *lxcpath;
struct cgroup_process_info *cgroup;
--
1.7.10.4
------------------------------------------------------------------------------
October Webinars: Code for Performance
Free Intel webinars can help you accelerate application performance.
Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from
the latest Intel processors and coprocessors. See abstracts and register >
http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk
_______________________________________________
Lxc-devel mailing list
Lxc-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/lxc-devel
