swapon: share get_swap_prober() with swaplabel to print uuid and label

The swapon(8) listing was almost complete, apart from label and uuid.
This change moves the code from swaplabel(8) to shared scope to be used
for printouts in other swap commands, such as swapon.

Adding this feature to lsblk(8) was a consideration, but lsblk is not
interested of swapfiles, so the swapon seems like a better option to add
this information.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>

1 files changed, 44 insertions, 0 deletions

diff --git a/sys-utils/swapon-common.c b/sys-utils/swapon-common.c
index 6dd7bacb1..203d5c4d0 100644
--- a/sys-utils/swapon-common.c
+++ b/sys-utils/swapon-common.c
@@ -1,6 +1,8 @@
+#include <blkid.h>
 
 #include "c.h"
 #include "nls.h"
+#include "swapheader.h"
 #include "swapon-common.h"
 #include "xalloc.h"
 
@@ -104,3 +106,45 @@ size_t numof_uuids(void)
 	return ulct;
 }
 
+blkid_probe get_swap_prober(const char *devname)
+{
+	blkid_probe pr;
+	int rc;
+	const char *version = NULL;
+	char *swap_filter[] = { "swap", NULL };
+
+	pr = blkid_new_probe_from_filename(devname);
+	if (!pr) {
+		warn(_("%s: unable to probe device"), devname);
+		return NULL;
+	}
+
+	blkid_probe_enable_superblocks(pr, TRUE);
+	blkid_probe_set_superblocks_flags(pr,
+			BLKID_SUBLKS_LABEL | BLKID_SUBLKS_UUID |
+			BLKID_SUBLKS_VERSION);
+
+	blkid_probe_filter_superblocks_type(pr, BLKID_FLTR_ONLYIN, swap_filter);
+
+	rc = blkid_do_safeprobe(pr);
+	if (rc == -1)
+		warn(_("%s: unable to probe device"), devname);
+	else if (rc == -2)
+		warnx(_("%s: ambivalent probing result, use wipefs(8)"), devname);
+	else if (rc == 1)
+		warnx(_("%s: not a valid swap partition"), devname);
+
+	if (rc == 0) {
+		/* Only the SWAPSPACE2 is supported. */
+		if (blkid_probe_lookup_value(pr, "VERSION", &version, NULL) == 0
+		    && version
+		    && strcmp(version, stringify_value(SWAP_VERSION)))
+			warnx(_("%s: unsupported swap version '%s'"),
+						devname, version);
+		else
+			return pr;
+	}
+
+	blkid_free_probe(pr);
+	return NULL;
+}