crtools: support any format of image path (v3)

Now a name of an image file is hard coded ("smth-%d.img", pid),
but the images of namespaces, shared memery, etc belong to
not one task, so they may have other formats of names, which
will describe objects.

For example a image of shared memory content may have name like
this ("pages-shmem-%ld.img", shmid)

v2: fix comment
v3: rebase
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

crtools.c

@@ -148,7 +148,7 @@ static struct cr_fdset *alloc_cr_fdset(void)
 
 	cr_fdset = xmalloc(sizeof(*cr_fdset));
 	if (cr_fdset)
-		for (i = 0; i < CR_FD_MAX; i++)
+		for (i = 0; i < CR_FD_PID_MAX; i++)
 			cr_fdset->fds[i] = -1;
 	return cr_fdset;
 }
@@ -160,7 +160,7 @@ void __close_cr_fdset(struct cr_fdset *cr_fdset)
 	if (!cr_fdset)
 		return;
 
-	for (i = 0; i < CR_FD_MAX; i++) {
+	for (i = 0; i < CR_FD_PID_MAX; i++) {
 		if (cr_fdset->fds[i] == -1)
 			continue;
 		close_safe(&cr_fdset->fds[i]);
@@ -185,7 +185,6 @@ static struct cr_fdset *cr_fdset_open(int pid, unsigned long use_mask,
 	struct cr_fdset *fdset;
 	unsigned int i;
 	int ret = -1;
-	char path[PATH_MAX];
 
 	/*
 	 * We either reuse existing fdset or create new one.
@@ -197,46 +196,22 @@ static struct cr_fdset *cr_fdset_open(int pid, unsigned long use_mask,
 	} else
 		fdset = cr_fdset;
 
-	for (i = 0; i < CR_FD_MAX; i++) {
+	for (i = 0; i < CR_FD_PID_MAX; i++) {
 		if (!(use_mask & CR_FD_DESC_USE(i)))
 			continue;
 
 		if (fdset->fds[i] != -1)
 			continue;
 
-		sprintf(path, fdset_template[i].fmt, pid);
-
-		if (flags & O_EXCL) {
-			ret = unlinkat(image_dir_fd, path, 0);
-			if (ret && errno != ENOENT) {
-				pr_perror("Unable to unlink %s", path);
-				goto err;
-			}
-		}
-
-		ret = openat(image_dir_fd, path, flags, CR_FD_PERM);
+		ret = open_image(i, flags, pid);
 		if (ret < 0) {
 			if (!(flags & O_CREAT))
 				/* caller should check himself */
 				continue;
-			pr_perror("Unable to open %s", path);
 			goto err;
 		}
-		fdset->fds[i] = ret;
-
-		if (flags == O_RDONLY) {
-			u32 magic;
 
-			if (read_img(ret, &magic) < 0)
-				goto err;
-			if (magic != fdset_template[i].magic) {
-				pr_err("Magic doesn't match for %s\n", path);
-				goto err;
-			}
-		} else {
-			if (write_img(ret, &fdset_template[i].magic))
-				goto err;
-		}
+		fdset->fds[i] = ret;
 	}
 
 	return fdset;

include/crtools.h

@@ -44,6 +44,8 @@ enum {
 
 	CR_FD_SK_QUEUES,
 
+	CR_FD_PID_MAX, /* fmt, pid */
+
 	CR_FD_MAX
 };
 
@@ -98,14 +100,16 @@ extern struct cr_fd_desc_tmpl fdset_template[CR_FD_MAX];
 extern int image_dir_fd;
 extern int open_image_dir(void);
 extern void close_image_dir(void);
-extern int open_image_ro(int type, int pid);
+
+int open_image(int type, unsigned long flags, ...);
+#define open_image_ro(type, ...) open_image(type, O_RDONLY, __VA_ARGS__);
 extern int open_image_ro_nocheck(const char *fmt, int pid);
 
 #define LAST_PID_PATH		"/proc/sys/kernel/ns_last_pid"
 #define LAST_PID_PERM		0666
 
 struct cr_fdset {
-	int fds[CR_FD_MAX];
+	int fds[CR_FD_PID_MAX];
 };
 
 #define CR_FD_DESC_USE(type)		((1 << (type)))

util.c

@@ -161,23 +161,47 @@ int open_image_ro_nocheck(const char *fmt, int pid)
 	return tmp;
 }
 
-int open_image_ro(int type, int pid)
+int open_image(int type, unsigned long flags, ...)
 {
-	int fd;
-	u32 magic = 0;
+	char path[PATH_MAX];
+	va_list args;
+	int ret;
 
-	fd = open_image_ro_nocheck(fdset_template[type].fmt, pid);
-	if (fd < 0)
-		return fd;
+	va_start(args, flags);
+	vsnprintf(path, PATH_MAX, fdset_template[type].fmt, args);
+	va_end(args);
+
+	if (flags & O_EXCL) {
+		ret = unlinkat(image_dir_fd, path, 0);
+		if (ret && errno != ENOENT) {
+			pr_perror("Unable to unlink %s", path);
+			goto err;
+		}
+	}
 
-	read(fd, &magic, sizeof(magic));
+	ret = openat(image_dir_fd, path, flags, CR_FD_PERM);
+	if (ret < 0) {
+		pr_perror("Unable to open %s", path);
+		goto err;
+	}
+
+	if (flags == O_RDONLY) {
+		u32 magic;
+
+		if (read_img(ret, &magic) < 0)
+			goto err;
 		if (magic != fdset_template[type].magic) {
-		pr_err("Magic mismatch for %d of %d\n", type, pid);
-		close(fd);
-		return -1;
+			pr_err("Magic doesn't match for %s\n", path);
+			goto err;
+		}
+	} else {
+		if (write_img(ret, &fdset_template[type].magic))
+			goto err;
 	}
 
-	return fd;
+	return ret;
+err:
+	return -1;
 }
 
 int image_dir_fd = -1;