libblkid: no more probe for btrfs backup superblock

 * Linux kernel cares about the first superblock only

 * backup superblock are FS specific stuff and there is no reason to
   care about it in generic tools

 * the problem with broken btrfs utils has been already fixed (it was
   possible to use the utils on filesystem with erased primary
   superblok without any warning message).

Signed-off-by: Karel Zak <kzak@redhat.com>

libblkid/src/blkid.h.in

@@ -329,7 +329,6 @@ extern blkid_parttable blkid_partlist_get_table(blkid_partlist ls);
 extern blkid_partition blkid_partlist_get_partition(blkid_partlist ls, int n);
 extern blkid_partition blkid_partlist_get_partition_by_partno(blkid_partlist ls, int n);
 extern blkid_partition blkid_partlist_devno_to_partition(blkid_partlist ls, dev_t devno);
-extern blkid_partition blkid_partlist_get_partition_by_partno(blkid_partlist ls, int n);
 extern blkid_parttable blkid_partition_get_table(blkid_partition par);
 
 extern const char *blkid_partition_get_name(blkid_partition par);

libblkid/src/blkidP.h

@@ -224,9 +224,6 @@ struct blkid_struct_probe
 
 /* private per-probing flags */
 #define BLKID_PROBE_FL_IGNORE_PT (1 << 1)	/* ignore partition table */
-#define BLKID_PROBE_FL_IGNORE_BACKUP (1 << 2)	/* ignore backup superblocks or PT */
-
-extern int blkid_probe_ignore_backup(blkid_probe pr);
 
 extern blkid_probe blkid_clone_probe(blkid_probe parent);
 extern blkid_probe blkid_probe_get_wholedisk_probe(blkid_probe pr);

libblkid/src/probe.c

@@ -934,7 +934,8 @@ int blkid_do_probe(blkid_probe pr)
  *
  * This function erases the current signature detected by @pr. The @pr has to
  * be open in O_RDWR mode, BLKID_SUBLKS_MAGIC or/and BLKID_PARTS_MAGIC flags
- * has to be enabled.
+ * has to be enabled (if you want to errase also superblock with broken check
+ * sums then use BLKID_SUBLKS_BADCSUM too).
  *
  * After successful signature removing the @pr prober will be moved one step
  * back and the next blkid_do_probe() call will again call previously called
@@ -1135,8 +1136,6 @@ int blkid_do_safeprobe(blkid_probe pr)
 
 	blkid_probe_start(pr);
 
-	pr->prob_flags |= BLKID_PROBE_FL_IGNORE_BACKUP;
-
 	for (i = 0; i < BLKID_NCHAINS; i++) {
 		struct blkid_chain *chn;
 
@@ -1809,8 +1808,3 @@ void blkid_probe_use_wiper(blkid_probe pr, blkid_loff_t off, blkid_loff_t size)
 		blkid_probe_chain_reset_vals(pr, chn);
 	}
 }
-
-int blkid_probe_ignore_backup(blkid_probe pr)
-{
-	return pr && (pr->prob_flags & BLKID_PROBE_FL_IGNORE_BACKUP);
-}

libblkid/src/superblocks/btrfs.c

@@ -63,11 +63,6 @@ static int probe_btrfs(blkid_probe pr, const struct blkid_idmag *mag)
 {
 	struct btrfs_super_block *bfs;
 
-	if (mag->kboff > 64 && blkid_probe_ignore_backup(pr)) {
-		DBG(LOWPROBE, blkid_debug("btrfs: found backup superblock, ignore"));
-		return 1;
-	}
-
 	bfs = blkid_probe_get_sb(pr, mag, struct btrfs_super_block);
 	if (!bfs)
 		return -1;
@@ -92,8 +87,6 @@ const struct blkid_idinfo btrfs_idinfo =
 	.magics		=
 	{
 	  { .magic = "_BHRfS_M", .len = 8, .sboff = 0x40, .kboff = 64 },
-	  { .magic = "_BHRfS_M", .len = 8, .sboff = 0x40, .kboff = 64 * 1024 },
-	  { .magic = "_BHRfS_M", .len = 8, .sboff = 0x40, .kboff = 256 * 1024 * 1024 },
 	  { NULL }
 	}
 };