On Thu, Sep 05, 2013 at 09:57:24PM +0000, Myklebust, Trond wrote: > On Thu, 2013-09-05 at 16:36 -0500, Quentin Barnes wrote: > > On Thu, Sep 05, 2013 at 08:02:01PM +0000, Myklebust, Trond wrote: > > > On Thu, 2013-09-05 at 14:11 -0500, Quentin Barnes wrote: > > > > On Thu, Sep 05, 2013 at 12:03:03PM -0500, Malahal Naineni wrote: > > > > > Neil Brown posted a patch couple days ago for this! > > > > > > > > > > http://thread.gmane.org/gmane.linux.nfs/58473 > > > > > > > > I tried Neil's patch on a v3.11 kernel. The rebuilt kernel still > > > > exhibited the same 1000s of WRITEs/sec problem. > > > > > > > > Any other ideas? > > > > > > Yes. Please try the attached patch. > > > > Great! That did the trick! > > > > Do you feel this patch could be worthy of pushing it upstream in its > > current state or was it just to verify a theory? > > > > > > In comparing the nfs_flush_incompatible() implementations between > > RHEL5 and v3.11 (without your patch), the guts of the algorithm seem > > more or less logically equivalent to me on whether or not to flush > > the page. Also, when and where nfs_flush_incompatible() is invoked > > seems the same. Would you provide a very brief pointer to clue me > > in as to why this problem didn't also manifest circa 2.6.18 days? > > There was no nfs_vm_page_mkwrite() to handle page faults in the 2.6.18 > days, and so the risk was that your mmapped writes could end up being > sent with the wrong credentials. Ah! You're right that nfs_vm_page_mkwrite() was missing from the original 2.6.18, so that makes sense, however, Red Hat had backported that function starting with their RHEL5.9(*) kernels, yet the problem doesn't manifest on RHEL5.9. Maybe the answer lies somewhere in RHEL5.9's do_wp_page(), or up that call path, but glancing through it, it all looks pretty close though. (*) That was the source I using when comparing with the 3.11 source when studying your patch since it was the last kernel known to me without the problem. > -- > Trond Myklebust > Linux NFS client maintainer > > NetApp > Trond.Myklebust@xxxxxxxxxx > www.netapp.com Quentin -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
