[CRIU] [PATCH 1/2] files-reg: Use global mutex to serialize ghost file creation

[Cyrill Gorcunov]

Otherwise there is a race between files with same names.

Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
---
 cr-restore.c        |    2 ++
 files-reg.c         |   17 ++++++++++++++++-
 include/files-reg.h |    2 ++
 3 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/cr-restore.c b/cr-restore.c
index 49c78e4..92c3175 100644
--- a/cr-restore.c
+++ b/cr-restore.c
@@ -94,6 +94,8 @@ static int prepare_shared(void)
 	if (prepare_shared_tty())
 		return -1;
 
+	if (prepare_shared_reg_files())
+		return -1;
 
 	if (collect_reg_files())
 		return -1;
diff --git a/files-reg.c b/files-reg.c
index b459130..6ffa6fa 100644
--- a/files-reg.c
+++ b/files-reg.c
@@ -43,6 +43,8 @@ struct ghost_file {
 static u32 ghost_file_ids = 1;
 static LIST_HEAD(ghost_files);
 
+mutex_t *ghost_file_mutex;
+
 /*
  * This constant is selected without any calculations. Just do not
  * want to pick up too big files with us in the image.
@@ -351,12 +353,14 @@ static int open_path(struct file_desc *d,
 
 	rfi = container_of(d, struct reg_file_info, d);
 
-	if (rfi->ghost)
+	if (rfi->ghost) {
+		mutex_lock(ghost_file_mutex);
 		if (link(rfi->ghost->path, rfi->path) < 0) {
 			pr_perror("Can't link %s -> %s\n",
 					rfi->ghost->path, rfi->path);
 			return -1;
 		}
+	}
 
 	tmp = open_cb(rfi, arg);
 	if (tmp < 0) {
@@ -370,6 +374,7 @@ static int open_path(struct file_desc *d,
 			pr_info("Unlink the ghost %s\n", rfi->ghost->path);
 			unlink(rfi->ghost->path);
 		}
+		mutex_unlock(ghost_file_mutex);
 	}
 
 	if (restore_fown(tmp, rfi->rfe->fown))
@@ -438,6 +443,16 @@ static int collect_one_regfile(void *o, ProtobufCMessage *base)
 	return 0;
 }
 
+int prepare_shared_reg_files(void)
+{
+	ghost_file_mutex = shmalloc(sizeof(*ghost_file_mutex));
+	if (!ghost_file_mutex)
+		return -1;
+
+	mutex_init(ghost_file_mutex);
+	return 0;
+}
+
 int collect_reg_files(void)
 {
 	int ret;
diff --git a/include/files-reg.h b/include/files-reg.h
index f728449..6064442 100644
--- a/include/files-reg.h
+++ b/include/files-reg.h
@@ -24,6 +24,8 @@ extern int open_path_by_id(u32 id, int (*open_cb)(struct reg_file_info *, void *
 extern void clear_ghost_files(void);
 extern int collect_reg_files(void);
 
+extern int prepare_shared_reg_files(void);
+
 extern int dump_reg_file(struct fd_parms *p, int lfd, const struct cr_fdset *cr_fdset);
 extern int dump_one_reg_file(int lfd, u32 id, const struct fd_parms *p);
 
-- 
1.7.7.6