[lxc-devel] [PATCH 1/1] snapshots: move snapshot directory

[Serge Hallyn]

Originally we kept snapshots under /var/lib/lxcsnaps.  If a
separate btrfs is mounted at /var/lib/lxc, then we can't
make btrfs snapshots under /var/lib/lxcsnaps.

This patch moves the default directory to /var/lib/lxc/lxcsnaps.
If /var/lib/lxcsnaps already exists, then use that.  Don't allow
any container to be used with the name 'lxcsnaps'.

Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
---
 src/lxc/lxccontainer.c | 49 +++++++++++++++++++++++++++++++++++++++----------
 src/lxc/lxccontainer.h |  4 ++--
 2 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
index c90b564..1059961 100644
--- a/src/lxc/lxccontainer.c
+++ b/src/lxc/lxccontainer.c
@@ -2823,16 +2823,42 @@ static int get_next_index(const char *lxcpath, char *cname)
 	}
 }
 
+static bool get_snappath_dir(struct lxc_container *c, char *snappath)
+{
+	int ret;
+	/*
+	 * If the old style snapshot path exists, use it
+	 * /var/lib/lxc -> /var/lib/lxcsnaps
+	 */
+	ret = snprintf(snappath, MAXPATHLEN, "%ssnaps", c->config_path);
+	if (ret < 0 || ret >= MAXPATHLEN)
+		return false;
+	if (dir_exists(snappath)) {
+		ret = snprintf(snappath, MAXPATHLEN, "%ssnaps/%s", c->config_path, c->name);
+		if (ret < 0 || ret >= MAXPATHLEN)
+			return false;
+		return true;
+	}
+
+	/*
+	 * Use the new style path
+	 * /var/lib/lxc -> /var/lib/lxc + /lxcsnaps/ + c->name + \0
+	 */
+	ret = snprintf(snappath, MAXPATHLEN, "%s/lxcsnaps/%s", c->config_path, c->name);
+	if (ret < 0 || ret >= MAXPATHLEN)
+		return false;
+	return true;
+}
+
 static int lxcapi_snapshot(struct lxc_container *c, const char *commentfile)
 {
 	int i, flags, ret;
 	struct lxc_container *c2;
 	char snappath[MAXPATHLEN], newname[20];
 
-	// /var/lib/lxc -> /var/lib/lxcsnaps \0
-	ret = snprintf(snappath, MAXPATHLEN, "%ssnaps/%s", c->config_path, c->name);
-	if (ret < 0 || ret >= MAXPATHLEN)
+	if (!get_snappath_dir(c, snappath)) {
 		return -1;
+	}
 	i = get_next_index(snappath, c->name);
 
 	if (mkdir_p(snappath, 0755) < 0) {
@@ -2966,7 +2992,7 @@ static char *get_timestamp(char* snappath, char *name)
 static int lxcapi_snapshot_list(struct lxc_container *c, struct lxc_snapshot **ret_snaps)
 {
 	char snappath[MAXPATHLEN], path2[MAXPATHLEN];
-	int dirlen, count = 0, ret;
+	int count = 0, ret;
 	struct dirent dirent, *direntp;
 	struct lxc_snapshot *snaps =NULL, *nsnaps;
 	DIR *dir;
@@ -2974,9 +3000,7 @@ static int lxcapi_snapshot_list(struct lxc_container *c, struct lxc_snapshot **r
 	if (!c || !lxcapi_is_defined(c))
 		return -1;
 
-	// snappath is ${lxcpath}snaps/${lxcname}/
-	dirlen = snprintf(snappath, MAXPATHLEN, "%ssnaps/%s", c->config_path, c->name);
-	if (dirlen < 0 || dirlen >= MAXPATHLEN) {
+	if (!get_snappath_dir(c, snappath)) {
 		ERROR("path name too long");
 		return -1;
 	}
@@ -3044,7 +3068,7 @@ out_free:
 static bool lxcapi_snapshot_restore(struct lxc_container *c, const char *snapname, const char *newname)
 {
 	char clonelxcpath[MAXPATHLEN];
-	int flags = 0,ret;
+	int flags = 0;
 	struct lxc_container *snap, *rest;
 	struct bdev *bdev;
 	bool b = false;
@@ -3067,8 +3091,7 @@ static bool lxcapi_snapshot_restore(struct lxc_container *c, const char *snapnam
 			return false;
 		}
 	}
-	ret = snprintf(clonelxcpath, MAXPATHLEN, "%ssnaps/%s", c->config_path, c->name);
-	if (ret < 0 || ret >= MAXPATHLEN) {
+	if (!get_snappath_dir(c, clonelxcpath)) {
 		bdev_put(bdev);
 		return false;
 	}
@@ -3284,6 +3307,12 @@ struct lxc_container *lxc_container_new(const char *name, const char *configpath
 {
 	struct lxc_container *c;
 
+	if (!name)
+		return NULL;
+
+	if (strcmp(name, "lxcsnaps") == 0)
+		return NULL;
+
 	c = malloc(sizeof(*c));
 	if (!c) {
 		fprintf(stderr, "failed to malloc lxc_container\n");
diff --git a/src/lxc/lxccontainer.h b/src/lxc/lxccontainer.h
index ba15ab7..946a662 100644
--- a/src/lxc/lxccontainer.h
+++ b/src/lxc/lxccontainer.h
@@ -649,7 +649,7 @@ struct lxc_container {
 	 * \brief Create a container snapshot.
 	 *
 	 * Assuming default paths, snapshots will be created as
-	 * \c /var/lib/lxcsnaps/\<c\>/snap\<n\>
+	 * \c /var/lib/lxc/lxcsnaps/\<c\>/snap\<n\>
 	 * where \c \<c\> represents the container name and \c \<n\>
 	 * represents the zero-based snapshot number.
 	 *
@@ -691,7 +691,7 @@ struct lxc_container {
 	 *  fail if the  snapshot is overlay-based, since the snapshots
 	 *  will pin the original container.
 	 * \note As an example, if the container exists as \c /var/lib/lxc/c1, snapname might be \c 'snap0'
-	 *  (representing \c /var/lib/lxcsnaps/c1/snap0). If \p newname is \p c2,
+	 *  (representing \c /var/lib/lxc/lxcsnaps/c1/snap0). If \p newname is \p c2,
 	 *  then \c snap0 will be copied to \c /var/lib/lxc/c2.
 	 */
 	bool (*snapshot_restore)(struct lxc_container *c, const char *snapname, const char *newname);
-- 
1.8.3.2