This is a patch we've written and applied in Ubuntu to improve the atomicity of devmapper device creation somewhat, and avoid races with udev. Scott -- Scott James Remnant scott@xxxxxxxxxx
--- devmapper-1.02.20.orig/lib/libdm-common.c
+++ devmapper-1.02.20/lib/libdm-common.c
@@ -252,12 +252,11 @@
static int _add_dev_node(const char *dev_name, uint32_t major, uint32_t minor,
uid_t uid, gid_t gid, mode_t mode)
{
- char path[PATH_MAX];
+ char path[PATH_MAX], tmppath[PATH_MAX + 7];
struct stat info;
dev_t dev = MKDEV(major, minor);
mode_t old_mask;
-
- _build_dev_path(path, sizeof(path), dev_name);
+ int retval;
if (stat(path, &info) >= 0) {
if (!S_ISBLK(info.st_mode)) {
@@ -269,31 +268,39 @@
/* If right inode already exists we don't touch uid etc. */
if (info.st_rdev == dev)
return 1;
-
- if (unlink(path) < 0) {
- log_error("Unable to unlink device node for '%s'",
- dev_name);
- return 0;
- }
}
+ _build_dev_path(path, sizeof(path), dev_name);
+ strcpy (tmppath, path);
+ strcat (tmppath, ".dm-tmp");
+
old_mask = umask(0);
- if (mknod(path, S_IFBLK | mode, dev) < 0) {
- log_error("Unable to make device node for '%s'", dev_name);
+ retval = mknod(tmppath, S_IFBLK | mode, dev);
+ umask(old_mask);
+ if (retval < 0) {
+ log_error("Unable to make temporary device node for '%s'", dev_name);
return 0;
}
- umask(old_mask);
- if (chown(path, uid, gid) < 0) {
+ if (chown(tmppath, uid, gid) < 0) {
log_error("%s: chown failed: %s", path, strerror(errno));
+ unlink(tmppath);
return 0;
}
#ifdef HAVE_SELINUX
- if (!dm_set_selinux_context(path, S_IFBLK))
+ if (!dm_set_selinux_context(tmppath, S_IFBLK)) {
+ unlink(tmppath);
return 0;
+ }
#endif
+ if (rename(tmppath, path) < 0) {
+ log_error("Unable to replace device node for '%s'", dev_name);
+ unlink(tmppath);
+ return 0;
+ }
+
return 1;
}
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