linux-kernel - Re: [PATCH] nfs: propagate fileid changed errors back to syscall

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Message-ID: <C71642EC-B9F9-4A7D-AD11-D169268460FE@redhat.com>
Date: Tue, 10 Dec 2024 07:11:43 -0500
From: Benjamin Coddington <bcodding@...hat.com>
To: Nikhil Jha <njha@...estreet.com>
Cc: Trond Myklebust <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>,
 linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfs: propagate fileid changed errors back to syscall

On 9 Dec 2024, at 12:39, Nikhil Jha wrote:

> Hello! This is the first kernel patch I have tried to upstream. I'm
> following along with the kernel newbies guide but apologies if I got
> anything wrong.
>
> Currently, if there is a mismatch in the request and response fileids in
> an NFS request, the kernel logs an error and attempts to return ESTALE.
> However, this error is currently dropped before it makes it all the way
> to userspace. This appears to be a mistake, since as far as I can tell
> that ESTALE value is never consumed from anywhere.
>
> Callstack for async NFS write, at time of error:
>
>         nfs_update_inode <- returns -ESTALE
>         nfs_refresh_inode_locked
>         nfs_writeback_update_inode <- error is dropped here
>         nfs3_write_done
>         nfs_writeback_done
>         nfs_pgio_result <- other errors are collected here
>         rpc_exit_task
>         __rpc_execute
>         rpc_async_schedule
>         process_one_work
>         worker_thread
>         kthread
>         ret_from_fork
>
> We ran into this issue ourselves, and seeing the -ESTALE in the kernel
> source code but not from userspace was surprising.
>
> I tested a rebased version of this patch on an el8 kernel (v6.1.114),
> and it seems to correctly propagate this error.
>
>> 8------------------------------------------------------8<
>
> If an NFS server returns a response with a different file id to the
> response, the kernel currently prints out an error and attempts to
> return -ESTALE. However, this -ESTALE value is never surfaced anywhere.

Hi Nikhil Jha,

Will this cause us to return -ESTALE to the application even if the WRITE
was successful?

Ben