On 2013/6/9 10:37, Zhao Hongjiang wrote: > On 2013/6/9 6:30, Theodore Ts'o wrote: >> On Sat, Jun 08, 2013 at 11:13:35AM +0800, Zhao Hongjiang wrote: >>> >>> I run xfstests #239 against mainline 3.10.0-rc3, unfortunately it failure in my QEMU. I run the >>> case a hundred times, it certainly hit the failure several times. The failure msg is as follow: >>> >>> FSTYP -- ext4 >>> PLATFORM -- Linux/x86_64 3.10.0-rc3-mainline >>> >>> generic/239 1s ... - output mismatch (see /home/zhj/xfstests/results/generic/239.out.bad) >>> --- tests/generic/239.out 2013-06-07 22:04:09.000000000 -0400 >>> +++ /home/zff/xfstests/results/generic/239.out.bad 2013-06-07 22:04:09.000000000 -0400 >>> @@ -1,2 +1,515 @@ >>> QA output created by 239 >>> +hostname: Host name lookup failure >> >> OK, so this hostname failure is weird; I'm not sure what's causing >> this, but this I presume unrelated to the failure at hand. >> >>> Silence is golden >>> +0: 0x0 >>> +1: 0x0 >>> +2: 0x0 >>> +3: 0x0 >> >> This indicates a problem. Test generic/239 is running >> aio-dio-hole-filling-race.c, which submits an asynchronous, direct I/O >> 4k write with a buffer containing non-zero contents to a sparse file, >> and once the I/O has completed, it uses pread to read it back, using >> the same descriptor, so it is doing the read using direct I/O. It >> then checks to see if the read returns zero or not. >> >> The "XX: 0x0" lines indicates that buffer is zero, which implies that >> somehow aio_complete() is getting called before the uninitialized to >> initialized conversion is taking place. I'm not seeing how this is >> happening, though, so I'm a bit puzzled. If there are any unwritten >> extents, we don't call aio_complete() in ext4_end_io_dio(), but >> instead the conversion is queued via a call to ext4_add_compete_io(), >> and and aio_done() is only called on the iocb after the conversion is >> complete. >> >> Can anyone see something that I might be missing? >> >> - Ted >> >> P.S. Zhao, what was the hardware that you using to find this failure? > > I'am use x86 and start a qumu-kvm to run the test. > >> I'm not seeing it, but then again if the failure is only happening >> once every few hundred runs that might explain it. I'm perhaps > > And as Christoph Hellwig said "the race is very easy to hit by using QEMU with > native AIO support on a sparse image, and the result is filesystem corruption > in the guest", i also run the test on the host, but nerver see the failure. Sorry, i run the test on host a hundred times again, there are six failures. > >> wondering if we should add a mode to aio-dio-hole-filling-race.c which >> allows it to try the race a large number of times, instead of just >> once. > > This seems necessary, i'll give a patch for this. > - Zhao >> >> P.P.S. One thought.... perhaps it might be useful to have a debug >> mode where we use queue_delayed_work() to submit the conversion >> request to the workqueue. It will of course make certain workloads >> run slow as molasses, but it might expose some races so we can see >> them more easily. >> >> . >> > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
