[CRIU] [PATCH 21/27] restore: look up root for each file

[Andrey Vagin]

mntns is looked up by mnt_id, then /proc/NS_PID/root is opened.

This part will be optimized in the "mount: add a fast path for
mntns_collect_root" patch and /proc/NS_PID/root will be opened,
only if NS_PID is not the same as in the previous case.

Signed-off-by: Andrey Vagin <avagin at openvz.org>
---
 files-reg.c          | 20 ++++++++++++++++++--
 include/proc_parse.h |  1 +
 mount.c              |  1 +
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/files-reg.c b/files-reg.c
index fba683b..8a1cf47 100644
--- a/files-reg.c
+++ b/files-reg.c
@@ -23,6 +23,7 @@
 #include "fs-magic.h"
 #include "asm/atomic.h"
 #include "namespaces.h"
+#include "proc_parse.h"
 
 #include "protobuf.h"
 #include "protobuf/regfile.pb-c.h"
@@ -615,9 +616,22 @@ int open_path(struct file_desc *d,
 	struct reg_file_info *rfi;
 	int tmp;
 	char *orig_path = NULL;
+	struct mount_info *m;
 
 	rfi = container_of(d, struct reg_file_info, d);
 
+	if (rfi->rfe->mnt_id >= 0) {
+		m = lookup_mnt_id(rfi->rfe->mnt_id);
+		if (m == NULL) {
+			pr_err("Unable to look up the %d mntns: %s\n",
+						rfi->rfe->mnt_id, rfi->path);
+			return -1;
+		}
+
+		if (mntns_collect_root(m->nsid->pid))
+			return -1;
+	}
+
 	if (rfi->remap) {
 		mutex_lock(ghost_file_mutex);
 		if (rfi_remap(rfi) < 0) {
@@ -679,9 +693,11 @@ int open_path(struct file_desc *d,
 static int do_open_reg_noseek_flags(struct reg_file_info *rfi, void *arg)
 {
 	u32 flags = *(u32 *)arg;
-	int fd;
+	int fd, mntns_root;
+
+	mntns_root = get_service_fd(ROOT_FD_OFF);
 
-	fd = open(rfi->path, flags);
+	fd = openat(mntns_root, rfi->path, flags);
 	if (fd < 0) {
 		pr_perror("Can't open file %s on restore", rfi->path);
 		return fd;
diff --git a/include/proc_parse.h b/include/proc_parse.h
index e516cae..fbcf901 100644
--- a/include/proc_parse.h
+++ b/include/proc_parse.h
@@ -116,6 +116,7 @@ struct mount_info {
 	int		is_file;
 	bool		is_ns_root;
 	struct mount_info *next;
+	struct ns_id	*nsid;
 
 	/* tree linkage */
 	struct mount_info *parent;
diff --git a/mount.c b/mount.c
index d606022..cc1c9cf 100644
--- a/mount.c
+++ b/mount.c
@@ -1474,6 +1474,7 @@ static int collect_mnt_from_image(struct mount_info **pms, struct ns_id *nsid)
 		if (!pm)
 			goto err;
 
+		pm->nsid = nsid;
 		pm->next = *pms;
 		*pms = pm;
 
-- 
1.8.5.3