Greg, On Thu, Feb 14, 2013 at 11:26:14AM -0800, Greg Kroah-Hartman wrote: > On Thu, Feb 14, 2013 at 11:07:30AM +1100, Dave Chinner wrote: > > [cc xfs@xxxxxxxxxxx] > > > > On Wed, Feb 13, 2013 at 08:18:45AM -0800, Greg Kroah-Hartman wrote: > > > On Wed, Feb 13, 2013 at 04:30:32PM +0100, Paolo Bonzini wrote: > > > > Il 01/02/2013 14:08, Greg Kroah-Hartman ha scritto: > > > > > 3.7-stable review patch. If anyone has any objections, please let me know. > > > > > > > > > > ------------------ > > > > > > > > > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > > > > > > > > > commit eb178619f930fa2ba2348de332a1ff1c66a31424 upstream. > > > > > > > > > > When _xfs_buf_find is passed an out of range address, it will fail > > > > > to find a relevant struct xfs_perag and oops with a null > > > > > dereference. This can happen when trying to walk a filesystem with a > > > > > metadata inode that has a partially corrupted extent map (i.e. the > > > > > block number returned is corrupt, but is otherwise intact) and we > > > > > try to read from the corrupted block address. > > > > > > > > > > In this case, just fail the lookup. If it is readahead being issued, > > > > > it will simply not be done, but if it is real read that fails we > > > > > will get an error being reported. Ideally this case should result > > > > > in an EFSCORRUPTED error being reported, but we cannot return an > > > > > error through xfs_buf_read() or xfs_buf_get() so this lookup failure > > > > > may result in ENOMEM or EIO errors being reported instead. > > > > > > > > It looks like this breaks xfs_growfs. See > > > > http://bugzilla.redhat.com/show_bug.cgi?id=909602. > > > > Entirely possible, as the filesystem size is not updated until after > > all the new metadata is written to disk. in 3.8, there's this commit: > > > > commit fd23683c3b1ab905cba61ea2981c156f4bf52845 > > Author: Dave Chinner <dchinner@xxxxxxxxxx> > > Date: Mon Nov 12 22:53:59 2012 +1100 > > > > xfs: growfs: use uncached buffers for new headers > > > > When writing the new AG headers to disk, we can't attach write > > verifiers because they have a dependency on the struct xfs-perag > > being attached to the buffer to be fully initialised and growfs > > can't fully initialise them until later in the process. > > > > The simplest way to avoid this problem is to use uncached buffers > > for writing the new headers. These buffers don't have the xfs-perag > > attached to them, so it's simple to detect in the write verifier and > > be able to skip the checks that need the xfs-perag. > > > > This enables us to attach the appropriate buffer ops to the buffer > > and henc calculate CRCs on the way to disk. IT also means that the > > buffer is torn down immediately, and so the first access to the AG > > headers will re-read the header from disk and perform full > > verification of the buffer. This way we also can catch corruptions > > due to problems that went undetected in growfs. > > > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> > > Reviewed-by Rich Johnston <rjohnston@xxxxxxx> > > Signed-off-by: Ben Myers <bpm@xxxxxxx> > > > > As part of the metadata verifier feature. It means that growfs no > > longer uses cached buffers, and hence does not pass through > > _xfs_buf_find() and hence will not trigger the beyond-EOFS that the > > above commit adds. > > > > > Ick, not good. > > > > > > Dave, any thoughts here? Should I drop this from the 3.7-stable queue? > > > > Yeah, drop it. > > > > But what I'm now wondering is how this patch got proposed for > > 3.7-stable. I don't recall seeing anything about this being > > proposed. > > > > <trolls email archives> > > > > Oh, it happened while I was at LCA and didn't have any access to Red > > Hat email and there was a private thread about it. By the time I > > read it the stable kernel was already released and so it immediately > > dropped from my attention. > > > > XFS Maintainers: Major process fail. Patches that are being proposed > > for backports need to be posted to the XFS list, reviewed and tested > > before saying they are OK to go. We have several growfs tests in > > xfstests would have failed if this was actually tested. > > > > Stable folk: This is the reason why I, quite frankly, don't want to > > support stable kernels *at all*. The overhead of backporting and > > testing a patch to a single kernel target to ensure there are no > > unintended regressions is significant, and there are so many stable > > kernels no it's just a waste of developer time to try to support > > them. And in this case, the process simply wasn't executed and an > > unintended regression that is >this close< to causing filesystem > > corruption slipped through to the stable series..... > > Ok, how about I never apply any xfs stable kernel patch, unless you send > it to stable@xxxxxxxxxxxxxxx? Dave has made it clear that he doesn't want to be involved in maintaining -stable kernels. However, my team at SGI is interested in maintaining -stable kernels. We're not going to use the fact that there is a risk of regression as an excuse to starve -stable of relevant fixes, just as we do not use it as an excuse to starve the upstream branch of feature content. > I have that rule in place for some other subsystems that don't want me > applying stuff that they aren't aware of, and have no problem doing the same > thing here. > > Just let me know. Here are the usual suspects: Ben Myers <bpm@xxxxxxx> Mark Tinguely <tinguely@xxxxxxx> Dave Chinner <dchinner@xxxxxxxxxx> Eric Sandeen <sandeen@xxxxxxxxxx> > I'll go revert this patch for the next 3.7-stable release. Much appreciated. Regards, Ben _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
