lkml.org 
[lkml]   [2010]   [Jun]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Wrong DIF guard tag on ext2 write
On Tue, Jun 01, 2010 at 02:09:05PM -0400, Chris Mason wrote:
> On Tue, Jun 01, 2010 at 04:54:53PM +0000, James Bottomley wrote:
> > On Tue, 2010-06-01 at 12:47 -0400, Chris Mason wrote:
> > > On Tue, Jun 01, 2010 at 10:29:30AM -0600, Matthew Wilcox wrote:
> > > > On Tue, Jun 01, 2010 at 09:49:51AM -0400, Chris Mason wrote:
> > > > > > I agree that a block based retry would close all the holes ... it just
> > > > > > doesn't look elegant to me that the fs will already be repeating the I/O
> > > > > > if it changed the page and so will block.
> > > > >
> > > > > We might not ever repeat the IO. We might change the page, write it,
> > > > > change it again, truncate the file and toss the page completely.
> > > >
> > > > Why does it matter that it was never written in that case?
> > >
> > > It matters is the storage layer is going to wait around for the block to
> > > be written again with a correct crc.
> >
> > Actually, I wasn't advocating that. I think block should return a guard
> > mismatch error. I think somewhere in filesystem writeout is the place
> > to decide whether the error was self induced or systematic.
>
> In that case the io error goes to the async page writeback bio-endio
> handlers. We don't have a reference on the inode and no ability to
> reliably restart the IO, but we can set a bit on the address space
> indicating that somewhere, sometime in the past we had an IO error.
>
> > For self
> > induced errors (as long as we can detect them) I think we can just
> > forget about it ... if the changed page is important, the I/O request
> > gets repeated (modulo the problem of too great a frequency of changes
> > leading to us never successfully writing it) or it gets dropped because
> > the file was truncated or the data deleted for some other reason.
>
> Sorry, how can we tell the errors that are self induced from the evil
> bit flipping cable induced errors?

Block layer should retry it with bounce pages. That would be a lot nicer
than forcing all upper layers to avoid the problem.



\
 
 \ /
  Last update: 2010-06-01 20:49    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site