linux-kernel - Re: [PATCH 2/4] fs: return writeback errors for IOCB_DONTCACHE in generic_write

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Message-ID: <a05cde7d15d85f2cee6eafdb69b1380c8b704207.camel@gmail.com>
Date: Tue, 04 Nov 2025 17:34:50 +0530
From: "Nirjhar Roy (IBM)" <nirjhar.roy.lists@...il.com>
To: Christoph Hellwig <hch@....de>, "Darrick J. Wong" <djwong@...nel.org>
Cc: Carlos Maiolino <cem@...nel.org>, Christian Brauner
 <brauner@...nel.org>,  Jan Kara <jack@...e.cz>, "Martin K. Petersen"
 <martin.petersen@...cle.com>,  linux-kernel@...r.kernel.org,
 linux-xfs@...r.kernel.org,  linux-fsdevel@...r.kernel.org,
 linux-raid@...r.kernel.org,  linux-block@...r.kernel.org
Subject: Re: [PATCH 2/4] fs: return writeback errors for IOCB_DONTCACHE in
 generic_write_sync

On Wed, 2025-10-29 at 17:37 +0100, Christoph Hellwig wrote:
> On Wed, Oct 29, 2025 at 09:01:01AM -0700, Darrick J. Wong wrote:
> > Hum.  So we kick writeback but don't wait for any of it to start, and
> > immediately sample wberr.  Does that mean that in the "bdev died" case,
> > the newly initiated writeback will have failed so quickly that
> > file_check_and_advance_wb_err will see that?
> 
> Yes, this is primarily about catching errors in the submission path
> before it reaches the device, which are returned synchronously.
So, what you are saying is file_check_and_advance_wb_err() will wait/block till the write back
request done in filemap_fdatawrite_range_kick() is completely submitted and there are no more
chances of write back failure?
--NR
> 
> > Or are we only reflecting
> > past write failures back to userspace on the *second* write after the
> > device dies?
> > 
> > It would be helpful to know which fstests break, btw.
> 
> generic/252 generic/329 xfs/237
>