Date: Tue, 2 Apr 2002 11:01:13 -0500 (EST) From: Bruce Campbell <bruce@engmail.uwaterloo.ca> To: stable@FreeBSD.ORG Subject: Re: nfs_fsync: not dirty error in 4.5-RELEASE (possible solution) Message-ID: <Pine.GSO.4.05.10204021057090.17772-100000@engmail.uwaterloo.ca> In-Reply-To: <200203292234.g2TMYpq67679@apollo.backplane.com>
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While I can't create this panic at will, I've now had 3 panics in 2 weeks
(2 in the last 24 hours), on 2 different machines, one running stock...
FreeBSD engpfile3.uwaterloo.ca 4.5-RELEASE FreeBSD 4.5-RELEASE #0:
Mon Jan 28 14:31:56 GMT 2002
murray@builder.freebsdmall.com:/usr/src/sys/compile/GENERIC i386
and have collected 2 kernel cores, for further investigation if needed.
I'm now building a test machine to try the possible solution.
On Fri, 29 Mar 2002, Matthew Dillon wrote:
> Ok, I am putting this back on the main list.
>
> After looking at a kernel core that Danny graciously provided, I believe
> I have located the problem.
>
> The core shows NFS panicing on a struct buf showing up on the vnode's
> v_dirtyblkhd list that is not marked B_DELWRI.
>
> After examining the core I found that the buffer was marked B_INVAL,
> and I found a case in brelse() where B_DELWRI is cleared on a buffer
> marked B_DELWRI|B_INVAL without moving it out of the vnode's v_dirtyblkhd
> list. Specifically, line 1214 if kern/vfs_bio.c:
>
> /*
> * If B_INVAL, clear B_DELWRI. We've already placed the buffer
> * on the correct queue.
> */
> if ((bp->b_flags & (B_INVAL|B_DELWRI)) == (B_INVAL|B_DELWRI)) {
> bp->b_flags &= ~B_DELWRI;
> --numdirtybuffers;
> numdirtywakeup(lodirtybuffers);
> }
>
> I believe that the correct fix is to change this code to:
>
> /*
> * If B_INVAL, clear B_DELWRI. We've already placed the buffer
> * on the correct queue.
> */
> if ((bp->b_flags & (B_INVAL|B_DELWRI)) == (B_INVAL|B_DELWRI))
> bundirty(bp);
>
> I would appreciate it if everyone who is able to easily reproduce this
> panic would test this fix and post your results back to the list. If
> this solves the problem I will commit it to -current and -stable.
>
> -Matt
> Matthew Dillon
> <dillon@backplane.com>
>
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