[CRIU] [PATCH RFC 1/2] mount: fs type helpers introduced

[Stanislav Kinsburskiy]

This helpers just hide statfs syscall, which is used only for one purpose: get
file system magic number.

Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
---
 files.c         |   10 ++++------
 include/mount.h |    3 +++
 kerndat.c       |    8 +++-----
 mount.c         |   33 ++++++++++++++++++++++++++++-----
 4 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/files.c b/files.c
index f605a51..3a96985 100644
--- a/files.c
+++ b/files.c
@@ -269,7 +269,7 @@ static int fill_fd_params(struct parasite_ctl *ctl, int fd, int lfd,
 				struct fd_opts *opts, struct fd_parms *p)
 {
 	int ret;
-	struct statfs fsbuf;
+	unsigned int fs_type;
 	struct fdinfo_common fdinfo = { .mnt_id = -1, .owner = ctl->pid.virt };
 
 	if (fstat(lfd, &p->stat) < 0) {
@@ -277,15 +277,13 @@ static int fill_fd_params(struct parasite_ctl *ctl, int fd, int lfd,
 		return -1;
 	}
 
-	if (fstatfs(lfd, &fsbuf) < 0) {
-		pr_perror("Can't statfs fd %d", lfd);
+	if (parse_fdinfo_pid(ctl->pid.real, fd, FD_TYPES__UND, NULL, &fdinfo))
 		return -1;
-	}
 
-	if (parse_fdinfo_pid(ctl->pid.real, fd, FD_TYPES__UND, NULL, &fdinfo))
+	if (get_fstype_by_fd(lfd, &fs_type))
 		return -1;
 
-	p->fs_type	= fsbuf.f_type;
+	p->fs_type	= fs_type;
 	p->ctl		= ctl;
 	p->fd		= fd;
 	p->pos		= fdinfo.pos;
diff --git a/include/mount.h b/include/mount.h
index b3bbdce..4989b41 100644
--- a/include/mount.h
+++ b/include/mount.h
@@ -126,4 +126,7 @@ extern int mntns_maybe_create_roots(void);
 extern int read_mnt_ns_img(void);
 extern void cleanup_mnt_ns(void);
 
+extern int get_fstype_by_fd(int fd, unsigned int *type);
+extern int get_fstype_by_path(const char *path, unsigned int *type);
+
 #endif /* __CR_MOUNT_H__ */
diff --git a/kerndat.c b/kerndat.c
index 696701d..af84902 100644
--- a/kerndat.c
+++ b/kerndat.c
@@ -198,13 +198,11 @@ static dev_t get_host_dev(unsigned int which)
 	}
 
 	if (kstat[which].fs_dev == 0) {
-		struct statfs fst;
+		unsigned int fs_type;
 		struct stat st;
 
-		if (statfs(kstat[which].path, &fst)) {
-			pr_perror("Unable to statefs %s", kstat[which].path);
+		if (get_fstype_by_path(kstat[which].path, &fs_type))
 			return 0;
-		}
 
 		/*
 		 * XXX: If the fs we need is not there, it still
@@ -212,7 +210,7 @@ static dev_t get_host_dev(unsigned int which)
 		 * mounted on the host.
 		 */
 
-		if (fst.f_type != kstat[which].magic) {
+		if (fs_type != kstat[which].magic) {
 			pr_err("%s isn't mount on the host\n", kstat[which].name);
 			return 0;
 		}
diff --git a/mount.c b/mount.c
index 747488b..f5d8773 100644
--- a/mount.c
+++ b/mount.c
@@ -213,6 +213,30 @@ struct mount_info *lookup_mnt_id(unsigned int id)
 	return __lookup_mnt_id(mntinfo, id);
 }
 
+int get_fstype_by_fd(int fd, unsigned int *type)
+{
+	struct statfs fst;
+
+	if (fstatfs(fd, &fst)) {
+		pr_perror("Unable to statfs fd %d", fd);
+		return -errno;
+	}
+	*type = fst.f_type;
+	return 0;
+}
+
+int get_fstype_by_path(const char *path, unsigned int *type)
+{
+	struct statfs fst;
+
+	if (statfs(path, &fst)) {
+		pr_perror("Unable to statfs %s", path);
+		return -errno;
+	}
+	*type = fst.f_type;
+	return 0;
+}
+
 struct mount_info *lookup_mnt_sdev(unsigned int s_dev)
 {
 	struct mount_info *m;
@@ -2607,13 +2631,12 @@ static int do_mount_one(struct mount_info *mi)
 		return -1;
 
 	if (mi->fstype->code == FSTYPE__UNSUPPORTED) {
-		struct statfs st;
+		unsigned int fs_type;
 
-		if (statfs(mi->mountpoint, &st)) {
-			pr_perror("Unable to statfs %s", mi->mountpoint);
+		if (get_fstype_by_path(mi->mountpoint, &fs_type))
 			return -1;
-		}
-		if (st.f_type == BTRFS_SUPER_MAGIC)
+
+		if (fstype == BTRFS_SUPER_MAGIC)
 			mi->fstype = find_fstype_by_name("btrfs");
 	}