From aab15415eddbfa800031cb9f6273ca8fcf59efb7 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Mon, 24 Sep 2012 12:26:03 +1000
Subject: Manage: fix checks for removal from a container.

We must only remove from a container if the device isn't a
member of any member array.
To check we look at the 'holders' directory in sysfs.

We currently skip that check if ->devname is "detached", however
that can never be true since the change that introduced
add_detached().

Also sysfs_unique_holder returns status in 'errno' which isn't
entirely safe as e.g. closedir() is probably allowed to clear it.

So make sysfs_unique_holder return an unambigious value, and us
it to decide what to report.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 sysfs.c | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

(limited to 'sysfs.c')

diff --git a/sysfs.c b/sysfs.c
index 0043d272..47294556 100644
--- a/sysfs.c
+++ b/sysfs.c
@@ -778,18 +778,22 @@ int sysfs_unique_holder(int devnum, long rdev)
 	 * and is the only holder.
 	 * we should be locked against races by
 	 * an O_EXCL on devnum
+	 * Return values:
+	 *  0 - not unique, not even a holder
+	 *  1 - unique, this is the only holder.
+	 *  2/3 - not unique, there is another holder
+	 * -1 - error, cannot find the holders
 	 */
 	DIR *dir;
 	struct dirent *de;
 	char dirname[100];
 	char l;
-	int found = 0;
+	int ret = 0;
 	sprintf(dirname, "/sys/dev/block/%d:%d/holders",
 		major(rdev), minor(rdev));
 	dir = opendir(dirname);
-	errno = ENOENT;
 	if (!dir)
-		return 0;
+		return -1;
 	l = strlen(dirname);
 	while ((de = readdir(dir)) != NULL) {
 		char buf[10];
@@ -807,8 +811,8 @@ int sysfs_unique_holder(int devnum, long rdev)
 		strcat(dirname+l, "/dev");
 		fd = open(dirname, O_RDONLY);
 		if (fd < 0) {
-			errno = ENOENT;
-			break;
+			/* Probably a race, just ignore this */
+			continue;
 		}
 		n = read(fd, buf, sizeof(buf)-1);
 		close(fd);
@@ -816,24 +820,18 @@ int sysfs_unique_holder(int devnum, long rdev)
 			continue;
 		buf[n] = 0;
 		if (sscanf(buf, "%d:%d%c", &mj, &mn, &c) != 3 ||
-		    c != '\n') {
-			errno = ENOENT;
-			break;
-		}
+		    c != '\n')
+			continue;
 		if (mj != MD_MAJOR)
 			mn = -1-(mn>>6);
 
-		if (devnum != mn) {
-			errno = EEXIST;
-			break;
-		}
-		found = 1;
+		if (devnum == mn)
+			ret |= 1;
+		else
+			ret |= 2;
 	}
 	closedir(dir);
-	if (de)
-		return 0;
-	else
-		return found;
+	return ret;
 }
 
 int sysfs_freeze_array(struct mdinfo *sra)
-- 
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