Messages in this thread | | | Date | Wed, 18 Jun 2008 12:27:12 +1000 | From | Bron Gondwana <> | Subject | Re: BUG: mmapfile/writev spurious zero bytes (x86_64/not i386, bisected, reproducable) |
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On Tue, Jun 17, 2008 at 02:20:49PM -0700, Linus Torvalds wrote: > > > On Tue, 17 Jun 2008, Linus Torvalds wrote: > > > > Hmm. Something like this *may* salvage it. > > > > Untested, so far (I'll reboot and test soon enough), but even if it fixes > > things, it's not really very good. > > Ok, so I just rebooted with this, and it does indeed fix the bug. > > I'd be happier with a more complete fix (ie being byte-accurate and > actually doing the partial copy when it hits a fault in the middle), but > this seems to be the minimal fix, and at least fixes the totally bogus > return values from the x86-64 __copy_user*() functions. > > Not that I checked that I got _all_ cases correct (and maybe there are > other versions of __copy_user that I missed entirely), but Bron's > test-case at least seems to work properly for me now. > > Bron? If you have a more complete test-suite (ie the real-world case that > made you find this), it would be good to verify the whole thing.
I have a real world test case using "cyr_dbtool" from Cyrus 2.3.12 on a known-bug-inducing piece of data (the key and value sizes in the example code were taken from that. Indeed, the example code started off building byte-for-byte identical files, then I changed it to write only a single character across the entire key and value so the hexdump was shorter)
I'll give it a go.
Bron.
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