[lxc-devel] [PATCH v5] Make overlayfs mounts work directly
Christian Brauner
christianvanbrauner at gmail.com
Wed Oct 7 16:47:57 UTC 2015
Fair enough. Should we then adapt do_lxcapi_clone() to replace any mountentries
that involve references to the original container with the name of the new
container or should we just have users do it manually? (Because currently the
presence of any lxc.mount.entry = ... overlay ... will prevent clones from
working out of the box... Maybe I'm just being pedantic here...)
On Wed, Oct 07, 2015 at 01:20:35PM +0000, Serge Hallyn wrote:
> mount targets when relative are relative to the mounted rootfs dir
> (with absolute paths under the *not-mounted* rootfs dir being auto-
> translated to being under the mounted rootfs dir).
>
> These paths would be relative to the containerdir. I think that's too
> confusing.
>
> Quoting Christian Brauner (christianvanbrauner at gmail.com):
> > I now wonder if it wouldn't be smarter to force users to specify relative paths
> > for upper and workdir
> >
> > lxc.mount.entry = /lower merged overlay lowerdir=/lower,upper=upper,workdir=workdir,create=dir
> >
> > and fill in the missing path in mount_entry_create_*_dirs(). Otherwise these
> > mounts won't work out of the box when a clone of the container is made and
> > started... Thoughts?
> >
> > On Tue, Oct 06, 2015 at 08:38:13PM +0200, Christian Brauner wrote:
> > > When users wanted to mount overlay directories with lxc.mount.entry they had to
> > > create upperdirs and workdirs beforehand in order to mount them. To create it
> > > for them we add the functions mount_entry_create_overlay_dirs() and
> > > mount_entry_create_aufs_dirs() which do this for them. User can now simply
> > > specify e.g.:
> > >
> > > lxc.mount.entry = /lower merged overlay lowerdir=/lower,upper=/upper,workdir=/workdir,create=dir
> > >
> > > and /upper and /workdir will be created for them. /upper and /workdir need to
> > > be absolute paths to directories which are created under the containerdir (e.g.
> > > under $lxcpath/CONTAINERNAME/). Relative mountpoints, mountpoints outside the
> > > containerdir, and mountpoints within the container's rootfs are ignored. (The
> > > latter *might* change in the future should it be considered safe/useful.)
> > >
> > > Specifying
> > >
> > > lxc.mount.entry = /lower merged overlay lowerdir=/lower:/lower2,create=dir
> > >
> > > will lead to a read-only overlay mount in accordance with the
> > > kernel-documentation.
> > >
> > > Specifying
> > >
> > > lxc.mount.entry = /lower merged overlay lowerdir=/lower,create=dir
> > >
> > > will fail when no upperdir and workdir options are given.
> > >
> > > Signed-off-by: Christian Brauner <christianvanbrauner at gmail.com>
> > > Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
> > > ---
> > > src/lxc/conf.c | 162 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----
> > > 1 file changed, 150 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> > > index 6728c78..5a3209a 100644
> > > --- a/src/lxc/conf.c
> > > +++ b/src/lxc/conf.c
> > > @@ -1815,13 +1815,151 @@ static void cull_mntent_opt(struct mntent *mntent)
> > > }
> > > }
> > >
> > > +static int mount_entry_create_overlay_dirs(const struct mntent *mntent,
> > > + const struct lxc_rootfs *rootfs)
> > > +{
> > > + char *del = NULL;
> > > + char *lxcpath = NULL;
> > > + char *upperdir = NULL;
> > > + char *workdir = NULL;
> > > + char **opts = NULL;
> > > + size_t arrlen = 0;
> > > + size_t dirlen = 0;
> > > + size_t i;
> > > + size_t len = 0;
> > > + size_t rootfslen = 0;
> > > +
> > > + if (!rootfs->path)
> > > + return -1;
> > > +
> > > + opts = lxc_string_split(mntent->mnt_opts, ',');
> > > + if (opts)
> > > + arrlen = lxc_array_len((void **)opts);
> > > + else
> > > + return -1;
> > > +
> > > + for (i = 0; i < arrlen; i++) {
> > > + if (strstr(opts[i], "upperdir=") && (strlen(opts[i]) > (len = strlen("upperdir="))))
> > > + upperdir = opts[i] + len;
> > > + else if (strstr(opts[i], "workdir=") && (strlen(opts[i]) > (len = strlen("workdir="))))
> > > + workdir = opts[i] + len;
> > > + }
> > > +
> > > + lxcpath = strdup(rootfs->path);
> > > + if (!lxcpath) {
> > > + lxc_free_array((void **)opts, free);
> > > + return -1;
> > > + }
> > > +
> > > + del = strstr(lxcpath, "/rootfs");
> > > + if (!del) {
> > > + free(lxcpath);
> > > + lxc_free_array((void **)opts, free);
> > > + return -1;
> > > + }
> > > + *del = '\0';
> > > +
> > > + dirlen = strlen(lxcpath);
> > > + rootfslen = strlen(rootfs->path);
> > > +
> > > + /* We neither allow users to create upperdirs and workdirs outside the
> > > + * containerdir nor inside the rootfs. The latter might be debatable. */
> > > + if (upperdir)
> > > + if ((strncmp(upperdir, lxcpath, dirlen) == 0) && (strncmp(upperdir, rootfs->path, rootfslen) != 0))
> > > + if (mkdir_p(upperdir, 0755) < 0) {
> > > + WARN("Failed to create upperdir");
> > > + }
> > > +
> > > +
> > > + if (workdir)
> > > + if ((strncmp(workdir, lxcpath, dirlen) == 0) && (strncmp(workdir, rootfs->path, rootfslen) != 0))
> > > + if (mkdir_p(workdir, 0755) < 0) {
> > > + WARN("Failed to create workdir");
> > > + }
> > > +
> > > + free(lxcpath);
> > > + lxc_free_array((void **)opts, free);
> > > + return 0;
> > > +}
> > > +
> > > +static int mount_entry_create_aufs_dirs(const struct mntent *mntent,
> > > + const struct lxc_rootfs *rootfs)
> > > +{
> > > + char *del = NULL;
> > > + char *lxcpath = NULL;
> > > + char *scratch = NULL;
> > > + char *tmp = NULL;
> > > + char *upperdir = NULL;
> > > + char **opts = NULL;
> > > + size_t arrlen = 0;
> > > + size_t i;
> > > + size_t len = 0;
> > > +
> > > + if (!rootfs->path)
> > > + return -1;
> > > +
> > > + opts = lxc_string_split(mntent->mnt_opts, ',');
> > > + if (opts)
> > > + arrlen = lxc_array_len((void **)opts);
> > > + else
> > > + return -1;
> > > +
> > > + for (i = 0; i < arrlen; i++) {
> > > + if (strstr(opts[i], "br=") && (strlen(opts[i]) > (len = strlen("br="))))
> > > + tmp = opts[i] + len;
> > > + }
> > > + if (!tmp) {
> > > + lxc_free_array((void **)opts, free);
> > > + return -1;
> > > + }
> > > +
> > > + upperdir = strtok_r(tmp, ":=", &scratch);
> > > + if (!upperdir) {
> > > + lxc_free_array((void **)opts, free);
> > > + return -1;
> > > + }
> > > +
> > > + lxcpath = strdup(rootfs->path);
> > > + if (!lxcpath) {
> > > + lxc_free_array((void **)opts, free);
> > > + return -1;
> > > + }
> > > +
> > > + del = strstr(lxcpath, "/rootfs");
> > > + if (!del) {
> > > + free(lxcpath);
> > > + lxc_free_array((void **)opts, free);
> > > + return -1;
> > > + }
> > > + *del = '\0';
> > > +
> > > + /* We neither allow users to create upperdirs outside the containerdir
> > > + * nor inside the rootfs. The latter might be debatable. */
> > > + if ((strncmp(upperdir, lxcpath, strlen(lxcpath)) == 0) && (strncmp(upperdir, rootfs->path, strlen(rootfs->path)) != 0))
> > > + if (mkdir_p(upperdir, 0755) < 0) {
> > > + WARN("Failed to create upperdir");
> > > + }
> > > +
> > > + free(lxcpath);
> > > + lxc_free_array((void **)opts, free);
> > > + return 0;
> > > +}
> > > +
> > > static int mount_entry_create_dir_file(const struct mntent *mntent,
> > > - const char* path)
> > > + const char* path, const struct lxc_rootfs *rootfs)
> > > {
> > > char *pathdirname = NULL;
> > > int ret = 0;
> > > FILE *pathfile = NULL;
> > >
> > > + if (strncmp(mntent->mnt_type, "overlay", 7) == 0) {
> > > + if (mount_entry_create_overlay_dirs(mntent, rootfs) < 0)
> > > + return -1;
> > > + } else if (strncmp(mntent->mnt_type, "aufs", 4) == 0) {
> > > + if (mount_entry_create_aufs_dirs(mntent, rootfs) < 0)
> > > + return -1;
> > > + }
> > > +
> > > if (hasmntopt(mntent, "create=dir")) {
> > > if (mkdir_p(path, 0755) < 0) {
> > > WARN("Failed to create mount target '%s'", path);
> > > @@ -1839,23 +1977,23 @@ static int mount_entry_create_dir_file(const struct mntent *mntent,
> > > if (!pathfile) {
> > > WARN("Failed to create mount target '%s'", path);
> > > ret = -1;
> > > - }
> > > - else
> > > + } else {
> > > fclose(pathfile);
> > > + }
> > > }
> > > free(pathdirname);
> > > return ret;
> > > }
> > >
> > > static inline int mount_entry_on_generic(struct mntent *mntent,
> > > - const char* path, const char *rootfs)
> > > + const char* path, const struct lxc_rootfs *rootfs)
> > > {
> > > unsigned long mntflags;
> > > char *mntdata;
> > > int ret;
> > > bool optional = hasmntopt(mntent, "optional") != NULL;
> > >
> > > - ret = mount_entry_create_dir_file(mntent, path);
> > > + ret = mount_entry_create_dir_file(mntent, path, rootfs);
> > >
> > > if (ret < 0)
> > > return optional ? 0 : -1;
> > > @@ -1867,11 +2005,11 @@ static inline int mount_entry_on_generic(struct mntent *mntent,
> > > return -1;
> > > }
> > >
> > > - ret = mount_entry(mntent->mnt_fsname, path, mntent->mnt_type,
> > > - mntflags, mntdata, optional, rootfs);
> > > + ret = mount_entry(mntent->mnt_fsname, path, mntent->mnt_type, mntflags,
> > > + mntdata, optional,
> > > + rootfs->path ? rootfs->mount : NULL);
> > >
> > > free(mntdata);
> > > -
> > > return ret;
> > > }
> > >
> > > @@ -1924,17 +2062,17 @@ skipabs:
> > > return -1;
> > > }
> > >
> > > - return mount_entry_on_generic(mntent, path, rootfs->mount);
> > > + return mount_entry_on_generic(mntent, path, rootfs);
> > > }
> > >
> > > static int mount_entry_on_relative_rootfs(struct mntent *mntent,
> > > - const char *rootfs)
> > > + const struct lxc_rootfs *rootfs)
> > > {
> > > char path[MAXPATHLEN];
> > > int ret;
> > >
> > > /* relative to root mount point */
> > > - ret = snprintf(path, sizeof(path), "%s/%s", rootfs, mntent->mnt_dir);
> > > + ret = snprintf(path, sizeof(path), "%s/%s", rootfs->mount, mntent->mnt_dir);
> > > if (ret >= sizeof(path)) {
> > > ERROR("path name too long");
> > > return -1;
> > > @@ -1961,7 +2099,7 @@ static int mount_file_entries(const struct lxc_rootfs *rootfs, FILE *file,
> > > /* We have a separate root, mounts are relative to it */
> > > if (mntent.mnt_dir[0] != '/') {
> > > if (mount_entry_on_relative_rootfs(&mntent,
> > > - rootfs->mount))
> > > + rootfs))
> > > goto out;
> > > continue;
> > > }
> > > --
> > > 2.6.1
> > >
>
>
>
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> > lxc-devel at lists.linuxcontainers.org
> > http://lists.linuxcontainers.org/listinfo/lxc-devel
>
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