Re: too many inodes error from fsck

[David Brownlee <abs%netbsd.org@localhost>]

On Thu, 8 Oct 2020 at 20:13, Greg Troxel <gdt%lexort.com@localhost> wrote:
>
> David Brownlee <abs%netbsd.org@localhost> writes:
>
> > I have a filesystem failing fsck with "bad inode number 34610688 to
> > nextinode" and its not in a convenient place to copy all data off to
> > rebuild, so I'd like to investigate options to clear the affected
> > inode.
> >
> > The message is triggered from pass1.c
> >
> >                 for (ii = 0; ii < inosused; ii++, inumber++) {
> >                         if (inumber < UFS_ROOTINO) {
> >                                 (void)getnextinode(inumber); /* <------ here */
> >                                 continue;
> >                         }
> >
> > Adding a quick printf before that loop of
> > printf("inumber %llu, inosused %lld\n", (unsigned long long)inumber,
> > (unsigned long long)inosused);
> > and tweaking the bad inode number message to include lastvalidnum
> >
> > gives a fair amount of output, ending with:
> >
> > inumber 34091008, inosused 11264
> > inumber 34194944, inosused 11264
> > inumber 34298880, inosused 11264
> > inumber 34402816, inosused 11264
> > inumber 34506752, inosused 839647232
> > bad inode number 34610688 (max 34610687) to nextinode
> >
> > "one of those things is not like the others".
> > It looks like we have a bad inosused, which runs off the end of the
> > available space (>.lastvalidinum) This feels like something from which
> > fsck could recover?
>
> Yes, I suppose it could write something, but it's hard to know how.
>
> I am guessing that in this case you have a sector with junk in it, when
> it should be inodes.   I wonder about using fsdb to look at it, or
> writing something to get a sector and just print the inodes by field
> value.
>
> This may be as simple as zeroing the bad sector.

So far in this case I think fsck has "fixed" the inodes up to
lastvalidnum, I wonder if a relatively conservative approach could be
to truncate inosused to lastvalidnum?

David