linux-kernel - Re: [PATCH] xfs: report a writeback error on a read() call

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Message-ID: <c77a55f5ab294be222c8abd86c2b8fddabca9f61.camel@kernel.org>
Date: Tue, 24 Jun 2025 14:26:18 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Christoph Hellwig <hch@...radead.org>, ying chen <yc1082463@...il.com>
Cc: djwong@...nel.org, linux-xfs@...r.kernel.org,
 linux-kernel@...r.kernel.org, 	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] xfs: report a writeback error on a read() call

On Tue, 2025-06-24 at 07:14 -0700, Christoph Hellwig wrote:
> On Sun, Jun 22, 2025 at 08:32:18PM +0800, ying chen wrote:
> > Normally, user space returns immediately after writing data to the
> > buffer cache. However, if an error occurs during the actual disk
> > write operation, data loss may ensue, and there is no way to report
> > this error back to user space immediately. Current kernels may report
> > writeback errors when fsync() is called, but frequent invocations of
> > fsync() can degrade performance. Therefore, a new sysctl
> > fs.xfs.report_writeback_error_on_read is introduced, which, when set
> > to 1, reports writeback errors when read() is called. This allows user
> > space to be notified of writeback errors more promptly.
> 
> That's really kernel wide policy and not something magic done by a
> single file system.

...not to mention that getting an error back on a read for a prior
writeback error would be completely unexpected by most applications.
-- 
Jeff Layton <jlayton@...nel.org>