[CRIU] [PATCH 4/5] files: Cleanup ghost subdirectories

[Cyrill Gorcunov]

In case if some of ghost directories has transient entries
which we had to creat while restoring they cause inability
to remove toplevel directory due to ENOTEMPTY error raised.

To address this we do the following:

 - when ghost entries are created remember which
   dentries were created in @remap->subdirs

 - when we're cleaning them up we remove these
   transient entries up to @remap->subdirs

Signed-off-by: Cyrill Gorcunov <gorcunov at gmail.com>
---
 criu/files-reg.c         | 51 ++++++++++++++++++++++++++++++++++++----
 criu/include/files-reg.h |  2 ++
 2 files changed, 49 insertions(+), 4 deletions(-)

diff --git a/criu/files-reg.c b/criu/files-reg.c
index a36b60142760..f304efa8c770 100644
--- a/criu/files-reg.c
+++ b/criu/files-reg.c
@@ -355,6 +355,7 @@ static int ghost_apply_metadata(const char *path, GhostFileEntry *gfe)
 
 static int create_ghost(struct ghost_file *gf, GhostFileEntry *gfe, struct cr_img *img)
 {
+	const char *subdir = NULL;
 	struct mount_info *mi;
 	char path[PATH_MAX];
 	int ret, root_len;
@@ -391,7 +392,8 @@ static int create_ghost(struct ghost_file *gf, GhostFileEntry *gfe, struct cr_im
 		if ((ret = mknod(path, gfe->mode, gfe->rdev)) < 0)
 			msg = "Can't create node for ghost dev";
 	} else if (S_ISDIR(gfe->mode)) {
-		if ((ret = mkdirpat(AT_FDCWD, path, gfe->mode)) < 0)
+		ret = mkdirpat_precise(AT_FDCWD, path, gfe->mode, &subdir);
+		if (ret < 0)
 			msg = "Can't make ghost dir";
 	} else {
 		if ((ret = mkreg_ghost(path, gfe, img)) < 0)
@@ -415,6 +417,14 @@ static int create_ghost(struct ghost_file *gf, GhostFileEntry *gfe, struct cr_im
 	strcpy(gf->remap.rpath, path + root_len);
 	pr_debug("Remap rpath is %s\n", gf->remap.rpath);
 
+	/*
+	 * Save nested dirs for better cleanup.
+	 */
+	if (subdir && subdir != path) {
+		gf->remap.subdir  = gf->remap.rpath;
+		gf->remap.subdir += subdir - path - root_len;
+	}
+
 	ret = -1;
 	if (ghost_apply_metadata(path, gfe))
 		goto err;
@@ -758,6 +768,9 @@ static int order_remap_dirs(void)
 			pr_debug("remap: ghost ord %3s %s\n",
 				 ri->rfi->remap->is_dir ? "dir" : "fil",
 				 ri->rfi->path);
+			if (ri->rfi->remap->subdir)
+				pr_debug("remap:\tnew subdir %s\n",
+					 ri->rfi->remap->subdir);
 		}
 	}
 
@@ -783,6 +796,31 @@ int prepare_remaps(void)
 	return ret ? : order_remap_dirs();
 }
 
+static int cleanup_subdir(int dirfd, struct file_remap *remap)
+{
+	char *pos;
+	int ret;
+
+	if (!remap->subdir)
+		return 0;
+
+	/*
+	 * Note that we're modifying @remap->rpath but
+	 * caller is dropping this variable a bit later
+	 * anyway!
+	 */
+	for (pos = strrchr(remap->subdir, '/'); pos;
+	     pos = strrchr(pos, '/')) {
+		*pos = '\0';
+		pr_debug("\tUnlink remap subdir %s\n", remap->rpath);
+		ret = unlinkat(dirfd, remap->rpath, AT_REMOVEDIR);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 static int clean_ghost_dir(int rmntns_root, struct remap_info *ri)
 {
 	struct file_remap *remap = ri->rfi->remap;
@@ -791,10 +829,15 @@ static int clean_ghost_dir(int rmntns_root, struct remap_info *ri)
 	 * When deleting ghost directories here is two issues:
 	 * - names might duplicate, so we may receive ENOENT
 	 *   and should not treat it as an error
+	 * - some ghost directories might have transient entries
+	 *   which we have to make during former path restoration
 	 */
-	if (ret)
-		return errno == ENOENT ? 0 : -errno;
-	return 0;
+	if (ret) {
+		if (errno == ENOENT)
+			ret = 0;
+	} else
+		ret = cleanup_subdir(rmntns_root, remap);
+	return ret;
 }
 
 static int clean_one_remap(struct remap_info *ri)
diff --git a/criu/include/files-reg.h b/criu/include/files-reg.h
index ec142db8c882..9b1339353878 100644
--- a/criu/include/files-reg.h
+++ b/criu/include/files-reg.h
@@ -10,6 +10,7 @@ struct cr_imgset;
 struct fd_parms;
 
 struct file_remap {
+	char *subdir;
 	char *rpath;
 	bool is_dir;
 	int  rmnt_id;
@@ -20,6 +21,7 @@ struct file_remap {
 static inline void file_remap_init(struct file_remap *remap)
 {
 	remap->rpath	= NULL;
+	remap->subdir	= NULL;
 	remap->is_dir	= false;
 	remap->uid	= -1;
 	remap->gid	= -1;
-- 
2.20.1