libblkid: improve whole-disk detection when read /proc/partitions

blkid(8) in high-level mode checks partitions and unpartitioned
whole-disk devices from the file /proc/partitions.

The current heuristic assumes that partition name ends with a digit.
Unfortunately, this is not correct -- for example md0 or nvme0n1 are
whole-disk devices.

This commit uses sysfs_devno_is_wholedisk() to make sure the device is
a partition (according to kernel or DM). It's probably more expensive,
because this way requires more syscalls (to read stuff from /sys etc.).

The patch also adds more information to the blkid(8) man page.

Addresses: https://github.com/karelzak/util-linux/issues/728
Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 14 insertions, 11 deletions

diff --git a/libblkid/src/devname.c b/libblkid/src/devname.c
index 986bcf241..129a349ac 100644
--- a/libblkid/src/devname.c
+++ b/libblkid/src/devname.c
@@ -452,6 +452,7 @@ static int probe_all(blkid_cache cache, int only_if_new)
 	char ptname0[128 + 1], ptname1[128 + 1], *ptname = NULL;
 	char *ptnames[2];
 	dev_t devs[2];
+	int iswhole[2] = { 0, 0 };
 	int ma, mi;
 	unsigned long long sz;
 	int lens[2] = { 0, 0 };
@@ -489,7 +490,7 @@ static int probe_all(blkid_cache cache, int only_if_new)
 			continue;
 		devs[which] = makedev(ma, mi);
 
-		DBG(DEVNAME, ul_debug("read partition name %s", ptname));
+		DBG(DEVNAME, ul_debug("read device name %s", ptname));
 
 		/* Skip whole disk devs unless they have no partitions.
 		 * If base name of device has changed, also
@@ -499,15 +500,14 @@ static int probe_all(blkid_cache cache, int only_if_new)
 		 *
 		 * Skip extended partitions.
 		 * heuristic: size is 1
-		 *
-		 * FIXME: skip /dev/{ida,cciss,rd} whole-disk devs
 		 */
 
 		lens[which] = strlen(ptname);
+		iswhole[which] = sysfs_devno_is_wholedisk(devs[which]);
 
-		/* ends in a digit, clearly a partition, so check */
-		if (isdigit(ptname[lens[which] - 1])) {
-			DBG(DEVNAME, ul_debug("partition dev %s, devno 0x%04X",
+		/* probably partition, so check */
+		if (!iswhole[which]) {
+			DBG(DEVNAME, ul_debug(" partition dev %s, devno 0x%04X",
 				   ptname, (unsigned int) devs[which]));
 
 			if (sz > 1)
@@ -521,7 +521,9 @@ static int probe_all(blkid_cache cache, int only_if_new)
 		 * on it, remove the whole-disk dev from the cache if
 		 * it exists.
 		 */
-		if (lens[last] && !strncmp(ptnames[last], ptname, lens[last])) {
+		if (lens[last] && iswhole[last]
+		    && !strncmp(ptnames[last], ptname, lens[last])) {
+
 			list_for_each_safe(p, pnext, &cache->bic_devs) {
 				blkid_dev tmp;
 
@@ -529,14 +531,14 @@ static int probe_all(blkid_cache cache, int only_if_new)
 				tmp = list_entry(p, struct blkid_struct_dev,
 						 bid_devs);
 				if (tmp->bid_devno == devs[last]) {
-					DBG(DEVNAME, ul_debug("freeing %s",
+					DBG(DEVNAME, ul_debug(" freeing %s",
 						       tmp->bid_name));
 					blkid_free_dev(tmp);
 					cache->bic_flags |= BLKID_BIC_FL_CHANGED;
 					break;
 				}
 			}
-			lens[last] = 0;
+			lens[last] = 0;		/* mark as checked */
 		}
 		/*
 		 * If last was not checked because it looked like a whole-disk
@@ -544,11 +546,12 @@ static int probe_all(blkid_cache cache, int only_if_new)
 		 * check last as well.
 		 */
 		if (lens[last] && strncmp(ptnames[last], ptname, lens[last])) {
-			DBG(DEVNAME, ul_debug("whole dev %s, devno 0x%04X",
+			DBG(DEVNAME, ul_debug(" whole dev %s, devno 0x%04X",
 				   ptnames[last], (unsigned int) devs[last]));
 			probe_one(cache, ptnames[last], devs[last], 0,
 				  only_if_new, 0);
-			lens[last] = 0;
+
+			lens[last] = 0;		/* mark as checked */
 		}
 	}