[CRIU] [PATCH v4 5/6] files-reg: Recreate deleted parent directories during restore of ghost file

[Pavel Emelyanov]

On 01/25/2016 07:40 PM, Kirill Tkhai wrote:
> This patch makes ghost files to restore with the right path.
> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---
>  files-reg.c |   97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 92 insertions(+), 5 deletions(-)
> 
> diff --git a/files-reg.c b/files-reg.c
> index b6c348a..dbe5e37 100644
> --- a/files-reg.c
> +++ b/files-reg.c
> @@ -1217,13 +1217,90 @@ static int linkat_hard(int odir, char *opath, int ndir, char *npath, uid_t owner
>  	return ret;
>  }
>  
> +/* Prints parent and returns place where last delimiter was */
> +static char *sprintf_parent_dir(char *dst, const char *path)
> +{
> +	char *p;
> +
> +	strcpy(dst, path);
> +
> +	p = strrchr(dst, '/');
> +	if (!p) {
> +		pr_err("Path %s has no parent dir", path);
> +		return NULL;
> +	}
> +	*p = '\0';
> +
> +	return p;
> +}
> +
> +static void rm_parent_dirs(int mntns_root, char *path, int count)
> +{
> +	char pdir[PATH_MAX], *p;
> +
> +	if (!count || !sprintf_parent_dir(pdir, path))
> +		return;
> +
> +	while (count--) {
> +		if (unlinkat(mntns_root, pdir, AT_REMOVEDIR))
> +			pr_perror("Can't remove %s AT %d", pdir, mntns_root);
> +		else
> +			pr_debug("Unlinked parent dir: %s AT %d\n", pdir, mntns_root);
> +
> +		p = strrchr(pdir, '/');
> +		if (p)
> +			*p = '\0';
> +	}
> +}
> +
> +/* Construct parent dir name and mkdir parent/grandparents if they're not exist */
> +static int make_parent_dirs_if_need(int mntns_root, char *path)
> +{
> +	char pdir[PATH_MAX], *p;

Too many PATH_MAX strings on the stack. Can we work directly on the path variable?

> +	int err, count = 0;
> +	struct stat st;
> +
> +	sprintf_parent_dir(pdir, path);
> +
> +	if (fstatat(mntns_root, pdir, &st, AT_EMPTY_PATH) == 0)

Is this fstatat() required? The below mkdir() would return EEXISTS anyway.

> +		return 0;
> +	if (errno != ENOENT) {
> +		pr_perror("Can't stat %s", pdir);
> +		return -1;
> +	}
> +
> +	p = pdir;
> +	do {
> +		p = strchr(p, '/');
> +		if (p)
> +			*p = '\0';
> +
> +		err = mkdirat(mntns_root, pdir, 0777);
> +		if (err && errno != EEXIST) {
> +			pr_perror("Can't create dir: %s AT %d", pdir, mntns_root);
> +			goto cleanup;
> +		} else if (!err) {
> +			pr_debug("Created parent dir: %s AT %d\n", pdir, mntns_root);
> +			count++;
> +		}
> +
> +		if (p)
> +			*p++ = '/';
> +	} while (p);
> +
> +	return count;
> +cleanup:
> +	rm_parent_dirs(mntns_root, pdir, count);
> +	return -1;
> +}
> +
>  /*
>   * This routine properly resolves d's path handling ghost/link-remaps.
>   * The open_cb is a routine that does actual open, it differs for
>   * files, directories, fifos, etc.
>   */
>  
> -static int rfi_remap(struct reg_file_info *rfi)
> +static int rfi_remap(struct reg_file_info *rfi, int *level)
>  {
>  	struct mount_info *mi, *rmi, *tmi;
>  	char _path[PATH_MAX], *path = _path;
> @@ -1269,14 +1346,23 @@ static int rfi_remap(struct reg_file_info *rfi)
>  	mntns_root = mntns_get_root_fd(tmi->nsid);
>  
>  out_root:
> -	return linkat_hard(mntns_root, rpath, mntns_root, path, rfi->remap->owner);
> +	*level = make_parent_dirs_if_need(mntns_root, path);
> +	if (*level < 0)
> +		return -1;
> +
> +	if (linkat_hard(mntns_root, rpath, mntns_root, path, rfi->remap->owner) < 0) {
> +		rm_parent_dirs(mntns_root, path, *level);
> +		return -1;
> +	}
> +
> +	return 0;
>  }
>  
>  int open_path(struct file_desc *d,
>  		int(*open_cb)(int mntns_root, struct reg_file_info *, void *), void *arg)
>  {
> +	int tmp, mntns_root, level;
>  	struct reg_file_info *rfi;
> -	int tmp, mntns_root;
>  	char *orig_path = NULL;
>  
>  	if (inherited_fd(d, &tmp))
> @@ -1292,7 +1378,7 @@ int open_path(struct file_desc *d,
>  			 */
>  			orig_path = rfi->path;
>  			rfi->path = rfi->remap->rpath;
> -		} else if (rfi_remap(rfi) < 0) {
> +		} else if (rfi_remap(rfi, &level) < 0) {
>  			static char tmp_path[PATH_MAX];
>  
>  			if (errno != EEXIST) {
> @@ -1316,7 +1402,7 @@ int open_path(struct file_desc *d,
>  			snprintf(tmp_path, sizeof(tmp_path), "%s.cr_link", orig_path);
>  			pr_debug("Fake %s -> %s link\n", rfi->path, rfi->remap->rpath);
>  
> -			if (rfi_remap(rfi) < 0) {
> +			if (rfi_remap(rfi, &level) < 0) {
>  				pr_perror("Can't create even fake link!");
>  				return -1;
>  			}
> @@ -1356,6 +1442,7 @@ int open_path(struct file_desc *d,
>  	if (rfi->remap) {
>  		if (!rfi->remap->is_dir) {
>  			unlinkat(mntns_root, rfi->path, 0);
> +			rm_parent_dirs(mntns_root, rfi->path, level);
>  		}
>  
>  		BUG_ON(!rfi->remap->users);
> 
> .
>