Dave Chinner wrote:
> On Wed, Sep 13, 2017 at 04:14:37PM +0900, Tetsuo Handa wrote:
> > Brian Foster wrote:
> > > I threw a kmemcheck enabled kernel on a couple boxes out of curiosity.
> > > I didn't reproduce anything related to XFS with the "allow partially
> > > uninit." option enabled, even after running a quick group run in
> > > xfstests. Without that option, I did see an xlog_write() splat on a
> > > rhel7 boot but it was preceded by a constant stream of other reports
> > > (__d_lookup(), link_path_walk(), etc.) and ultimately resulted in a
> > > failed/hung bootup (after quite some time). I'm in the process of seeing
> > > a similar result on a Fedora vm running for-next. This isn't really
> > > debuggable in the current form due to the volume of preceding errors,
> > > the required boot time and the fact that my machines ultimately fall
> > > over.
> > >
> > > Do you see different behavior? Do you have the "allow partially
> > > uninitialized memory" option enabled or disabled? I wonder if there are
> > > fixes for these other errors I'm seeing in linux-next that XFS for-next
> > > hasn't picked up yet..?
> >
> > When I tested using linux-next-20170901, xlog_write() was the first splat
> > (after I workarounded take_dentry_name_snapshot() splat).
> > Today I retested using linux.git with a different VM and got a different result.
> >
> > Here are console log and kernel config as of 6d8ef53e8b2fed8b ("Merge tag 'f2fs-for-4.14'
> > of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs") on linux.git .
> >
> > http://I-love.SAKURA.ne.jp/tmp/serial-20170913.txt.xz
> > http://I-love.SAKURA.ne.jp/tmp/config-4.13-20170913
> >
> >
> > CONFIG_HAVE_ARCH_KMEMCHECK=y
> > CONFIG_KMEMCHECK=y
> > # CONFIG_KMEMCHECK_DISABLED_BY_DEFAULT is not set
> > CONFIG_KMEMCHECK_ENABLED_BY_DEFAULT=y
> > # CONFIG_KMEMCHECK_ONESHOT_BY_DEFAULT is not set
> > CONFIG_KMEMCHECK_QUEUE_SIZE=64
> > CONFIG_KMEMCHECK_SHADOW_COPY_SHIFT=5
> > CONFIG_KMEMCHECK_PARTIAL_OK=y
> > # CONFIG_KMEMCHECK_BITOPS_OK is not set
> >
> > ----------
> > Mounting Huge Pages File System...
> >
> > [ OK ] Stopped target Switch Root.
> >
> > [ OK ] Stopped target Initrd File Systems.[ 1054.691505] WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (ffff880135396660)
> > [ 1054.691506] 000000000000000093050a200000000000000000000000000000000000000000
> > [ 1054.691511] u u u u u u u u i i i i i i i i u u u u u u u u u u u u u u u u
> > [ 1054.691515] ^
> > [ 1054.691519] RIP: 0010:xlog_write+0x344/0x6b0
>
> What line of code does this correspond to?
>
/*
* Copy region.
*
* Unmount records just log an opheader, so can have
* empty payloads with no data region to copy. Hence we
* only copy the payload if the vector says it has data
* to copy.
*/
ASSERT(copy_len >= 0);
if (copy_len > 0) {
memcpy(ptr, reg->i_addr + copy_off, copy_len); // <= xlog_write+0x344/0x6b0
xlog_write_adv_cnt(&ptr, &len, &log_offset,
copy_len);
}
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