[libmultipath] care for read-only alias file

On bootup, the bindings file in can't be written to.
This was causing multipath to not check it for aliases.
Now, it the bindings file is on a read-only filesystem,
it will be opened read-only.

diff --git a/libmultipath/alias.c b/libmultipath/alias.c
index 02ca087..ca434fe 100644 (file)
--- a/libmultipath/alias.c
+++ b/libmultipath/alias.c
@@ -120,21 +120,34 @@ lock_bindings_file(int fd)
 
 
 static int
-open_bindings_file(char *file)
+open_bindings_file(char *file, int *can_write)
 {
        int fd;
        struct stat s;
 
        if (ensure_directories_exist(file, 0700))
                return -1;
+       *can_write = 1;
        fd = open(file, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
        if (fd < 0) {
-               condlog(0, "Cannot open bindings file [%s] : %s", file,
-                       strerror(errno));
-               return -1;
+               if (errno == EROFS) {
+                       *can_write = 0;
+                       condlog(3, "Cannot open bindings file [%s] read/write. "
+                               " trying readonly", file);
+                       fd = open(file, O_RDONLY);
+                       if (fd < 0) {
+                               condlog(0, "Cannot open bindings file [%s] "
+                                       "readonly : %s", file, strerror(errno));
+                               return -1;
+                       }
+               }
+               else {
+                       condlog(0, "Cannot open bindings file [%s] : %s", file,
+                               strerror(errno));
+                       return -1;
+               }
        }
-
-       if (lock_bindings_file(fd) < 0)
+       if (*can_write && lock_bindings_file(fd) < 0)
                goto fail;
        
        memset(&s, 0, sizeof(s));
@@ -143,6 +156,8 @@ open_bindings_file(char *file)
                goto fail;
        }
        if (s.st_size == 0) {
+               if (*can_write == 0)
+                       goto fail;
                /* If bindings file is empty, write the header */
                size_t len = strlen(BINDINGS_FILE_HEADER);
                if (write_all(fd, BINDINGS_FILE_HEADER, len) != len) {
@@ -297,13 +312,14 @@ get_user_friendly_alias(char *wwid, char *file)
        char *alias;
        int fd, scan_fd, id;
        FILE *f;
+       int can_write;
 
        if (!wwid || *wwid == '\0') {
                condlog(3, "Cannot find binding for empty WWID");
                return NULL;
        }
 
-       fd = open_bindings_file(file);
+       fd = open_bindings_file(file, &can_write);
        if (fd < 0)
                return NULL;
 
@@ -332,7 +348,7 @@ get_user_friendly_alias(char *wwid, char *file)
                return NULL;
        }
 
-       if (!alias)
+       if (!alias && can_write)
                alias = allocate_binding(fd, wwid, id);
 
        fclose(f);
@@ -345,7 +361,7 @@ char *
 get_user_friendly_wwid(char *alias, char *file)
 {
        char *wwid;
-       int fd, scan_fd, id;
+       int fd, scan_fd, id, unused;
        FILE *f;
 
        if (!alias || *alias == '\0') {
@@ -353,7 +369,7 @@ get_user_friendly_wwid(char *alias, char *file)
                return NULL;
        }
 
-       fd = open_bindings_file(file);
+       fd = open_bindings_file(file, &unused);
        if (fd < 0)
                return NULL;