swapon: Canonicalize swap device

Swapon checks whether a swap device is active by searching for the
device name in /proc/swaps. /proc/swaps always specifies the path
to real device file, even if the path to real device file, even
if symlink was passed to the swapon() system call.

This differs from /proc/mounts semantics where each string contains
exactly the same device name as it was passed to the mount*() system call.

If a swap partition resides on lvm, libblkid returns a name in
form /dev/mapper/*, but now there are symlinks pointing to device
files /dev/dm-*, resulting to /proc/swaps containing /dev/dm-*,
but swapon still looks for /dev/mapper/* and tries to activate
the swap partition again.

[kzak@redhat.com: - remove unnecessary changes from
                    is_in_proc_swaps()]

Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
Tested-by: Petr Uzel <petr.uzel@suse.cz>
Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/mount/swapon.c b/mount/swapon.c
index a2dd9dc26..812884711 100644
--- a/mount/swapon.c
+++ b/mount/swapon.c
@@ -23,6 +23,7 @@
 #include "pathnames.h"
 #include "swapheader.h"
 #include "mangle.h"
+#include "canonicalize.h"
 
 #define PATH_MKSWAP	"/sbin/mkswap"
 
@@ -177,11 +178,16 @@ read_proc_swaps(void) {
 			break;
 		swapFiles = q;
 
-		swapFiles[numSwaps++] = unmangle(line);
+		if ((p = unmangle(line)) == NULL)
+			break;
+
+		swapFiles[numSwaps++] = canonicalize_path(p);
+		free(p);
 	}
 	fclose(swaps);
 }
 
+/* note that swapFiles are always canonicalized */
 static int
 is_in_proc_swaps(const char *fname) {
 	int i;