NeilBrown: Allow dev_open to work on read-only /dev

[Martin F. Krafft]

Module: mdadm
Branch: upstream
Commit: 6df6a774bff2fc6e2ab3f4092620ab7657c984aa
URL:    http://git.debian.org/?p=pkg-mdadm/mdadm.git;a=commit;h=6df6a774bff2fc6e2ab3f4092620ab7657c984aa

Author: NeilBrown <neilb at suse.de>
Date:   Mon Aug 30 08:48:48 2010 +1000

Allow dev_open to work on read-only /dev

/dev could be read-only in which case we cannot make devices
there.
So dev_open should first try to use an existing device name,
and if that doesn't work try creating a node in /dev or /tmp.

Reported-by:  Paweł Sikora <pluto at agmk.net>
Signed-off-by: NeilBrown <neilb at suse.de>

---

 util.c |   26 ++++++++++++++++++++------
 1 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/util.c b/util.c
index 0b9949a..c9bdd6e 100644
--- a/util.c
+++ b/util.c
@@ -959,19 +959,33 @@ int dev_open(char *dev, int flags)
 	int minor;
 
 	if (!dev) return -1;
+	flags |= O_DIRECT;
 
 	major = strtoul(dev, &e, 0);
 	if (e > dev && *e == ':' && e[1] &&
 	    (minor = strtoul(e+1, &e, 0)) >= 0 &&
 	    *e == 0) {
-		snprintf(devname, sizeof(devname), "/dev/.tmp.md.%d:%d:%d",
-			 (int)getpid(), major, minor);
-		if (mknod(devname, S_IFBLK|0600, makedev(major, minor))==0) {
-			fd = open(devname, flags|O_DIRECT);
-			unlink(devname);
+		char *path = map_dev(major, minor, 0);
+		if (path)
+			fd = open(path, flags);
+		if (fd < 0) {
+			snprintf(devname, sizeof(devname), "/dev/.tmp.md.%d:%d:%d",
+				 (int)getpid(), major, minor);
+			if (mknod(devname, S_IFBLK|0600, makedev(major, minor))==0) {
+				fd = open(devname, flags);
+				unlink(devname);
+			}
+		}
+		if (fd < 0) {
+			snprintf(devname, sizeof(devname), "/tmp/.tmp.md.%d:%d:%d",
+				 (int)getpid(), major, minor);
+			if (mknod(devname, S_IFBLK|0600, makedev(major, minor))==0) {
+				fd = open(devname, flags);
+				unlink(devname);
+			}
 		}
 	} else
-		fd = open(dev, flags|O_DIRECT);
+		fd = open(dev, flags);
 	return fd;
 }