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

[Jeff Layton]

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@xxxxxxxxxx>