udev: Fit into the standard rule sequencev1.0.2

Move the rule to run a bit later, after
the standard udev rules have called blkid.

Don't run blkid manually, and run probe-bcache
as a fallback which can be patched out in a
package that depends on util-linux 2.24+.

probe-bcache: bail if libblkid finds anything
Preserve our last-resort safety check here
in case earlier rules fail to call blkid.

1 files changed, 14 insertions, 0 deletions

diff --git a/probe-bcache.c b/probe-bcache.c
index e1ad614..c94c972 100644
--- a/probe-bcache.c
+++ b/probe-bcache.c
@@ -8,6 +8,7 @@
 #define __USE_FILE_OFFSET64
 #define _XOPEN_SOURCE 500
 
+#include <blkid.h>
 #include <fcntl.h>
 #include <linux/fs.h>
 #include <stdbool.h>
@@ -30,6 +31,7 @@ int main(int argc, char **argv)
 	extern char *optarg;
 	struct cache_sb sb;
 	char uuid[40];
+	blkid_probe pr;
 
 	while ((o = getopt(argc, argv, "o:")) != EOF)
 		switch (o) {
@@ -51,6 +53,18 @@ int main(int argc, char **argv)
 		if (fd == -1)
 			continue;
 
+		if (!(pr = blkid_new_probe()))
+			continue;
+		if (blkid_probe_set_device(pr, fd, 0, 0))
+			continue;
+		/* probe partitions too */
+		if (blkid_probe_enable_partitions(pr, true))
+			continue;
+		/* bail if anything was found
+		 * probe-bcache isn't needed once blkid recognizes bcache */
+		if (!blkid_do_probe(pr)) {
+			continue;
+		}
 
 		if (pread(fd, &sb, sizeof(sb), SB_START) != sizeof(sb))
 			continue;