[lxc-devel] [PATCH v5] Make overlayfs mounts work directly

Serge Hallyn serge.hallyn at ubuntu.com
Thu Oct 8 14:59:37 UTC 2015


Yes, I think so.  Worse, I think that'll mean we'll have to also restore
those at snapshot restore.

Quoting Christian Brauner (christianvanbrauner at gmail.com):
> 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
> > > > 
> > 
> > 
> > 
> > > _______________________________________________
> > > lxc-devel mailing list
> > > lxc-devel at lists.linuxcontainers.org
> > > http://lists.linuxcontainers.org/listinfo/lxc-devel
> > 
> > _______________________________________________
> > lxc-devel mailing list
> > lxc-devel at lists.linuxcontainers.org
> > http://lists.linuxcontainers.org/listinfo/lxc-devel



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