linux-ext4 - Re: [PATCH 17/17] xfs: support for synchronous DAX faults

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 27 Oct 2017 11:13:01 +0200
From:   Jan Kara <jack@...e.cz>
To:     Christoph Hellwig <hch@....de>
Cc:     Jan Kara <jack@...e.cz>, Dave Chinner <david@...morbit.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Christoph Hellwig <hch@...radead.org>,
        linux-ext4@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-api@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 17/17] xfs: support for synchronous DAX faults

On Fri 27-10-17 08:43:01, Christoph Hellwig wrote:
> On Thu, Oct 26, 2017 at 05:48:04PM +0200, Jan Kara wrote:
> > But now that I look at XFS implementation again, it misses handling
> > of VM_FAULT_NEEDSYNC in xfs_filemap_pfn_mkwrite() (ext4 gets this right).
> > I'll fix this by using __xfs_filemap_fault() for xfs_filemap_pfn_mkwrite()
> > as well since it mostly duplicates it anyway... Thanks for inquiring!
> 
> My first patches move xfs_filemap_pfn_mkwrite to use __xfs_filemap_fault,
> but that didn't work.  Wish I'd remember why, though.

Maybe due to the additional check on IS_DAX(inode) in __xfs_filemap_fault()
which could do the wrong thing if per-inode DAX flag is switched? Because
otherwise __xfs_filemap_fault(vmf, PE_SIZE_PTE, true) does exactly the same
thing as xfs_filemap_pfn_mkwrite() did.

If we do care about per-inode DAX flag switching, I can just fixup
xfs_filemap_pfn_mkwrite() but my understanding was that we ditched the idea
at least until someone comes up with a reliable way to implement that...

							Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR