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overlayfs_clone: rsync the mounted rootfs

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Closes #655

We can't rsync the delta as unpriv user because we can't create
the chardevs representing a whiteout.  We can however rsync the
rootfs and have the kernel create the whiteouts for us.

do_rsync: pass --delete

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>
This commit is contained in:
Serge Hallyn
2015-09-17 17:26:12 +00:00
committed by Stéphane Graber
parent ffe9a25a03
commit 186bef0024
1 changed files with 70 additions and 14 deletions
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84
src/lxc/bdev.c
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@@ -72,6 +72,11 @@
lxc_log_define(bdev, lxc);
struct ovl_rsync_data {
struct bdev *orig;
struct bdev *new;
};
struct rsync_data_char {
char *src;
char *dest;
@@ -98,7 +103,7 @@ static int do_rsync(const char *src, const char *dest)
s[l-2] = '/';
s[l-1] = '\0';
execlp("rsync", "rsync", "-aHX", s, dest, (char *)NULL);
execlp("rsync", "rsync", "-aHX", "--delete", s, dest, (char *)NULL);
exit(1);
}
@@ -2328,6 +2333,68 @@ static int rsync_delta_wrapper(void *data)
return rsync_delta(arg);
}
static int ovl_rsync(struct ovl_rsync_data *data)
{
if (setgid(0) < 0) {
ERROR("Failed to setgid to 0");
return -1;
}
if (setgroups(0, NULL) < 0)
WARN("Failed to clear groups");
if (setuid(0) < 0) {
ERROR("Failed to setuid to 0");
return -1;
}
if (unshare(CLONE_NEWNS) < 0) {
SYSERROR("Unable to unshare mounts ns");
return -1;
}
if (detect_shared_rootfs()) {
if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL)) {
SYSERROR("Failed to make / rslave");
ERROR("Continuing...");
}
}
if (overlayfs_mount(data->orig) < 0) {
ERROR("Failed mounting original container fs");
return -1;
}
if (overlayfs_mount(data->new) < 0) {
ERROR("Failed mounting new container fs");
return -1;
}
if (do_rsync(data->orig->dest, data->new->dest) < 0) {
ERROR("rsyncing %s to %s", data->orig->dest, data->new->dest);
return -1;
}
return 0;
}
static int ovl_rsync_wrapper(void *data)
{
struct ovl_rsync_data *arg = data;
return ovl_rsync(arg);
}
static int ovl_do_rsync(struct bdev *orig, struct bdev *new, struct lxc_conf *conf)
{
int ret = -1;
struct ovl_rsync_data rdata;
rdata.orig = orig;
rdata.new = new;
if (am_unpriv())
ret = userns_exec_1(conf, ovl_rsync_wrapper, &rdata);
else
ret = ovl_rsync(&rdata);
if (ret)
ERROR("copying overlayfs delta");
return ret;
}
static int overlayfs_clonepaths(struct bdev *orig, struct bdev *new, const char *oldname,
const char *cname, const char *oldpath, const char *lxcpath, int snap,
uint64_t newsize, struct lxc_conf *conf)
@@ -2460,19 +2527,6 @@ static int overlayfs_clonepaths(struct bdev *orig, struct bdev *new, const char
WARN("Failed to update ownership of %s", work);
free(work);
struct rsync_data_char rdata;
rdata.src = odelta;
rdata.dest = ndelta;
if (am_unpriv())
ret = userns_exec_1(conf, rsync_delta_wrapper, &rdata);
else
ret = rsync_delta(&rdata);
if (ret) {
free(osrc);
free(ndelta);
ERROR("copying overlayfs delta");
return -1;
}
len = strlen(nsrc) + strlen(ndelta) + 12;
new->src = malloc(len);
if (!new->src) {
@@ -2485,6 +2539,8 @@ static int overlayfs_clonepaths(struct bdev *orig, struct bdev *new, const char
free(ndelta);
if (ret < 0 || ret >= len)
return -ENOMEM;
return ovl_do_rsync(orig, new, conf);
} else {
ERROR("overlayfs clone of %s container is not yet supported",
orig->type);