Make background fsck based summary adjustments actually work by

initializing the sysctl mibs data before actually using them.

The original patchset (which is the actual version that is running
on my testboxes) have checked whether all of these sysctls and
refuses to do background fsck if we don't have them.  Kirk has
pointed out that refusing running fsck on old kernels is pointless,
as old kernels will recompute the summary at mount time, so I
have removed these checks.

Unfortunatelly, as the checks will initialize the mib values of
those sysctl's, and which are vital for the runtime summary
adjustment to work, we can not simply remove the check, which
will lead to problem when running background fsck over a dirty
volume.  Add these checks in a different way: give a warning rather
than refusing to work, and complain if the functionality is not
available when adjustments are necessary.

Noticed by:	A power failure at my lab
Pointy hat:	me
MFC After:	3 days

1 files changed, 18 insertions, 0 deletions

diff --git a/sbin/fsck_ffs/setup.c b/sbin/fsck_ffs/setup.c
index e95a6ad..f6b736d 100644
--- a/sbin/fsck_ffs/setup.c
+++ b/sbin/fsck_ffs/setup.c
@@ -140,6 +140,24 @@ setup(char *dev)
 			pfatal("kernel lacks background fsck support\n");
 			exit(EEXIT);
 		}
+		/*
+		 * When kernel is lack of runtime bgfsck superblock summary
+		 * adjustment functionality, it does not mean we can not
+		 * continue, as old kernels will recompute the summary at
+		 * mount time.  However, it will be an unexpected softupdates
+		 * inconsistency if it turns out that the summary is still
+		 * incorrect.  Set a flag so subsequent operation can know
+		 * this.
+		 */
+		bkgrdsumadj = 1;
+		if (sysctlnametomib("vfs.ffs.adjndir", adjndir, &size) < 0 ||
+		    sysctlnametomib("vfs.ffs.adjnbfree", adjnbfree, &size) < 0 ||
+		    sysctlnametomib("vfs.ffs.adjnifree", adjnifree, &size) < 0 ||
+		    sysctlnametomib("vfs.ffs.adjnffree", adjnffree, &size) < 0 ||
+		    sysctlnametomib("vfs.ffs.adjnumclusters", adjnumclusters, &size) < 0) {
+			bkgrdsumadj = 0;
+			pwarn("kernel lacks runtime superblock summary adjustment support");
+		}
 		cmd.version = FFS_CMD_VERSION;
 		cmd.handle = fsreadfd;
 		fswritefd = -1;