[lxc-devel] [PATCH] Add support for new create=(dir, file) mount option

[Serge Hallyn]

Quoting Stéphane Graber (stgraber at ubuntu.com):
> Just like we already had "optional", this adds two new LXC-specific
> mount flags:
>  - create=dir (will do a mkdir_p on the path)
>  - create=file (will do a mkdir_p on the dirname + a fopen on the path)
> 
> This was motivated by some of the needed bind-mounts for the
> unprivileged containers.
> 
> Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>

Hopefully someone finds time to commonize the code :)

Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>

> ---
>  src/lxc/conf.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 69 insertions(+), 1 deletion(-)
> 
> diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> index 6542ce1..0beb12b 100644
> --- a/src/lxc/conf.c
> +++ b/src/lxc/conf.c
> @@ -1906,18 +1906,41 @@ static inline int mount_entry_on_systemfs(struct mntent *mntent)
>  	unsigned long mntflags;
>  	char *mntdata;
>  	int ret;
> +	FILE *pathfile = NULL;
> +	char* pathdirname = NULL;
>  
>  	if (parse_mntopts(mntent->mnt_opts, &mntflags, &mntdata) < 0) {
>  		ERROR("failed to parse mount option '%s'", mntent->mnt_opts);
>  		return -1;
>  	}
>  
> +	if (hasmntopt(mntent, "create=dir")) {
> +		if (!mkdir_p(mntent->mnt_dir, 0755)) {
> +			WARN("Failed to create mount target '%s'", mntent->mnt_dir);
> +			ret = -1;
> +		}
> +	}
> +
> +	if (hasmntopt(mntent, "create=file") && access(mntent->mnt_dir, F_OK)) {
> +		pathdirname = strdup(mntent->mnt_dir);
> +		pathdirname = dirname(pathdirname);
> +		mkdir_p(pathdirname, 0755);
> +		pathfile = fopen(mntent->mnt_dir, "wb");
> +		if (!pathfile) {
> +			WARN("Failed to create mount target '%s'", mntent->mnt_dir);
> +			ret = -1;
> +		}
> +		else
> +			fclose(pathfile);
> +	}
> +
>  	ret = mount_entry(mntent->mnt_fsname, mntent->mnt_dir,
>  			  mntent->mnt_type, mntflags, mntdata);
>  
>  	if (hasmntopt(mntent, "optional") != NULL)
>  		ret = 0;
>  
> +	free(pathdirname);
>  	free(mntdata);
>  
>  	return ret;
> @@ -1933,6 +1956,8 @@ static int mount_entry_on_absolute_rootfs(struct mntent *mntent,
>  	char *mntdata;
>  	int r, ret = 0, offset;
>  	const char *lxcpath;
> +	FILE *pathfile = NULL;
> +	char *pathdirname = NULL;
>  
>  	if (parse_mntopts(mntent->mnt_opts, &mntflags, &mntdata) < 0) {
>  		ERROR("failed to parse mount option '%s'", mntent->mnt_opts);
> @@ -1975,6 +2000,25 @@ skipabs:
>  		goto out;
>  	}
>  
> +	if (hasmntopt(mntent, "create=dir")) {
> +		if (!mkdir_p(path, 0755)) {
> +			WARN("Failed to create mount target '%s'", path);
> +			ret = -1;
> +		}
> +	}
> +
> +	if (hasmntopt(mntent, "create=file") && access(path, F_OK)) {
> +		pathdirname = strdup(path);
> +		pathdirname = dirname(pathdirname);
> +		mkdir_p(pathdirname, 0755);
> +		pathfile = fopen(path, "wb");
> +		if (!pathfile) {
> +			WARN("Failed to create mount target '%s'", path);
> +			ret = -1;
> +		}
> +		else
> +			fclose(pathfile);
> +	}
>  
>  	ret = mount_entry(mntent->mnt_fsname, path, mntent->mnt_type,
>  			  mntflags, mntdata);
> @@ -1983,6 +2027,7 @@ skipabs:
>  		ret = 0;
>  
>  out:
> +	free(pathdirname);
>  	free(mntdata);
>  	return ret;
>  }
> @@ -1994,25 +2039,48 @@ static int mount_entry_on_relative_rootfs(struct mntent *mntent,
>  	unsigned long mntflags;
>  	char *mntdata;
>  	int ret;
> +	FILE *pathfile = NULL;
> +	char *pathdirname = NULL;
>  
>  	if (parse_mntopts(mntent->mnt_opts, &mntflags, &mntdata) < 0) {
>  		ERROR("failed to parse mount option '%s'", mntent->mnt_opts);
>  		return -1;
>  	}
>  
> -        /* relative to root mount point */
> +	/* relative to root mount point */
>  	ret = snprintf(path, sizeof(path), "%s/%s", rootfs, mntent->mnt_dir);
>  	if (ret >= sizeof(path)) {
>  		ERROR("path name too long");
>  		return -1;
>  	}
>  
> +	if (hasmntopt(mntent, "create=dir")) {
> +		if (!mkdir_p(path, 0755)) {
> +			WARN("Failed to create mount target '%s'", path);
> +			ret = -1;
> +		}
> +	}
> +
> +	if (hasmntopt(mntent, "create=file") && access(path, F_OK)) {
> +		pathdirname = strdup(path);
> +		pathdirname = dirname(pathdirname);
> +		mkdir_p(pathdirname, 0755);
> +		pathfile = fopen(path, "wb");
> +		if (!pathfile) {
> +			WARN("Failed to create mount target '%s'", path);
> +			ret = -1;
> +		}
> +		else
> +			fclose(pathfile);
> +	}
> +
>  	ret = mount_entry(mntent->mnt_fsname, path, mntent->mnt_type,
>  			  mntflags, mntdata);
>  
>  	if (hasmntopt(mntent, "optional") != NULL)
>  		ret = 0;
>  
> +	free(pathdirname);
>  	free(mntdata);
>  
>  	return ret;
> -- 
> 1.8.5.1
> 
> 
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