Exit fsck_ffs with non-zero status when file system is not repaired.

[dab]

Summary

When the fsck_ffs program cannot fully repair a file system,
it will output the message PLEASE RERUN FSCK. However, it does not
exit with a non-zero status in this case (contradicting the man page
claim that it "exits with 0 on success, and >0 if an error occurs."
The fsck rc-script (when running "fsck -y") tests the status from fsck
(which passes along the exit status from fsck_ffs) and issues a
"stop_boot" if the status fails. However, this is not effective since
fsck_ffs can return zero even on (some) errors. Effectively, it is
left to a later step in the boot process when the file systems are
mounted to detect the still-unclean file system and stop the boot.

This change modifies fsck_ffs so that when it cannot fully repair the
file system and issues the PLEASE RERUN FSCK message it also exits
with a non-zero status.

While here, the fsck_ffs man page has also been updated to document
the failing exit status codes used by fsck_ffs. Previously, only exit
status 7 was documented. Some of these exit statuses are tested for in
the fsck rc-script, so they are clearly depended upon and deserve
documentation.

Test Plan

Run fsck_ffs under the debugger on a file system. Force the
"rerun" flag to be set. Make sure that the exit status is non-zero
(and, specifically, equal to the new ERERUN define in fsck.h).

[mckusick]

This looks like a sensible and long overdue change.

[jilles]

sbin/fsck_ffs/fsck_ffs.8

386 ↗

(On Diff #37806)

Consider adding markup like

a
.Dv SIGQUIT
was received

406–412 ↗

(On Diff #37806)

Note that it is not arbitrary that many of these are powers of two. When fsck(8) runs checks on multiple filesystems, it combines their exit statuses using bitwise OR.

[dab]

sbin/fsck_ffs/fsck_ffs.8

406–412 ↗

(On Diff #37806)

You are correct. I was debating whether I should add a note to that effect, but whether it does or does not end up OR-ing statuses for multiple file systems together isn't entirely straightforward. Sometimes it will return a status and loop to the next file system, sometimes it will simply exit() with the status from a single (un-clean) file system.

[dab]

Somehow inadvertently removed jilles when I posted that last comment; add jilles back.

[dab]

Update the man page as suggested by jilles in review.

[mckusick]

Approve of latest change.