linux-kernel - Re: [PATCH - take 2] knfsd: nfsd: Handle ERESTARTSYS from syscalls.

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Date:	Fri, 20 Jun 2008 13:34:17 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	NeilBrown <neilb@...e.de>
Cc:	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH - take 2] knfsd: nfsd: Handle ERESTARTSYS from syscalls.

Thanks, applied (and replaced the earlier patch in the for-2.6.27 branch
at

	git://linux-nfs.org/~bfields/linux.git for-2.6.27

I saw sort of curious if I could convince myself to go through this
cycle only appending to that branch.  I guess not.  Maybe next time.)

--b.

On Thu, Jun 19, 2008 at 10:11:09AM +1000, NeilBrown wrote:
> 
> OCFS2 can return -ERESTARTSYS from write requests (and possibly
> elsewhere) if there is a signal pending.
> 
> If nfsd is shutdown (by sending a signal to each thread) while there
> is still an IO load from the client, each thread could handle one last
> request with a signal pending.  This can result in -ERESTARTSYS
> which is not understood by nfserrno() and so is reflected back to
> the client as nfserr_io aka -EIO.  This is wrong.
> 
> Instead, interpret ERESTARTSYS to mean "try again later" by returning
> nfserr_jukebox.  The client will resend and - if the server is
> restarted - the write will (hopefully) be successful and everyone will
> be happy.
> 
>  The symptom that I narrowed down to this was:
>     copy a large file via NFS to an OCFS2 filesystem, and restart
>     the nfs server during the copy.
>     The 'cp' might get an -EIO, and the file will be corrupted -
>     presumably holes in the middle where writes appeared to fail.
> 
> 
> Signed-off-by: Neil Brown <neilb@...e.de>
> 
> ### Diffstat output
>  ./fs/nfsd/nfsproc.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff .prev/fs/nfsd/nfsproc.c ./fs/nfsd/nfsproc.c
> --- .prev/fs/nfsd/nfsproc.c	2008-06-19 10:06:36.000000000 +1000
> +++ ./fs/nfsd/nfsproc.c	2008-06-19 10:07:58.000000000 +1000
> @@ -614,6 +614,7 @@ nfserrno (int errno)
>  #endif
>  		{ nfserr_stale, -ESTALE },
>  		{ nfserr_jukebox, -ETIMEDOUT },
> +		{ nfserr_jukebox, -ERESTARTSYS },
>  		{ nfserr_dropit, -EAGAIN },
>  		{ nfserr_dropit, -ENOMEM },
>  		{ nfserr_badname, -ESRCH },
--
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