[CRIU] [PATCH 2/2] files: Order ghost directories enties

[Cyrill Gorcunov]

Ghost files may lay inside ghost directories so we should
order their cleanup to eliminate situation where we remove
toplevel directory which still has not yet cleaned up entries

 | (00.002446) Unlink remap static/unlink_dir.test/0.cr.1.ghost
 | (00.002461) Unlink remap static/unlink_dir.test/1.cr.2.ghost
 | (00.002467) Unlink remap static/unlink_dir.test/gd1/gd2
 | (00.002477) Error (criu/files-reg.c:794): Couldn't unlink remap / static/unlink_dir.test/gd1/gd2: Directory not empty
 | (00.002480) Unlink remap static/unlink_dir.test/gd1/gd2/2.cr.4.ghost
 | (00.002490) Unlink remap static/unlink_dir.test/gd1/gd2/3.cr.5.ghost

For this sake we simply move ghost dirs into temp list, sort them
and move back but already sorted.

Signed-off-by: Cyrill Gorcunov <gorcunov at gmail.com>
---
 criu/files-reg.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 69 insertions(+), 1 deletion(-)

diff --git a/criu/files-reg.c b/criu/files-reg.c
index 892b62304d3a..d3058e0af7f8 100644
--- a/criu/files-reg.c
+++ b/criu/files-reg.c
@@ -42,6 +42,7 @@
 
 #include "files-reg.h"
 #include "plugin.h"
+#include "criu-log.h"
 
 int setfsuid(uid_t fsuid);
 int setfsgid(gid_t fsuid);
@@ -675,6 +676,72 @@ static int prepare_one_remap(struct remap_info *ri)
 	return ret;
 }
 
+static int remap_info_cmp(const void *_a, const void *_b)
+{
+	struct remap_info *a = ((struct remap_info **)_a)[0];
+	struct remap_info *b = ((struct remap_info **)_b)[0];
+	return -strcmp(a->rfi->path, b->rfi->path);
+}
+
+/*
+ * Ghost directories may carry ghost files but file descriptors
+ * are unordered in compare with this ghost paths, thus on cleanup
+ * we might try to remove the directory itself without waiting
+ * all files (and subdirectories) are cleaned up first.
+ *
+ * What we do here is we're move all ghost dirs into own list,
+ * sort them (to address subdirectories order) and move back
+ * to the end of the remap list.
+ */
+static int order_remap_dirs(void)
+{
+	struct remap_info *ri, *tmp;
+	struct remap_info **p, **t;
+	size_t nr_remaps = 0, i;
+	LIST_HEAD(ghost_dirs);
+
+	list_for_each_entry_safe(ri, tmp, &remaps, list) {
+		if (ri->rpe->remap_type != REMAP_TYPE__GHOST)
+			continue;
+		if (!ri->rfi->remap->is_dir)
+			continue;
+		list_move_tail(&ri->list, &ghost_dirs);
+		nr_remaps++;
+	}
+
+	if (list_empty(&ghost_dirs))
+		return 0;
+
+	p = t = xmalloc(sizeof(*p) * nr_remaps);
+	if (!p) {
+		list_splice_tail_init(&ghost_dirs, &remaps);
+		return -ENOMEM;
+	}
+
+	list_for_each_entry_safe(ri, tmp, &ghost_dirs, list) {
+		list_del_init(&ri->list);
+		p[0] = ri, p++;
+	}
+
+	qsort(t, nr_remaps, sizeof(t[0]), remap_info_cmp);
+
+	for (i = 0; i < nr_remaps; i++) {
+		list_add_tail(&t[i]->list, &remaps);
+		pr_debug("remap: ghost mov %s\n", t[i]->rfi->path);
+	}
+
+	if (!pr_quelled(LOG_DEBUG)) {
+		list_for_each_entry_safe(ri, tmp, &remaps, list) {
+			if (ri->rpe->remap_type != REMAP_TYPE__GHOST)
+				continue;
+			pr_debug("remap: ghost ord %s\n", ri->rfi->path);
+		}
+	}
+
+	xfree(t);
+	return 0;
+}
+
 int prepare_remaps(void)
 {
 	struct remap_info *ri;
@@ -690,7 +757,7 @@ int prepare_remaps(void)
 			break;
 	}
 
-	return ret;
+	return ret ? : order_remap_dirs();
 }
 
 static int clean_one_remap(struct remap_info *ri)
@@ -753,6 +820,7 @@ static struct collect_image_info remap_cinfo = {
 	.pb_type = PB_REMAP_FPATH,
 	.priv_size = sizeof(struct remap_info),
 	.collect = collect_one_remap,
+	.flags = COLLECT_SHARED,
 };
 
 /* Tiny files don't need to generate chunks in ghost image. */
-- 
2.20.1