Re: f2fs stability problems keep me from testing

[Marc Lehmann <schmorp@schmorp.de>]

On Thu, Nov 19, 2015 at 04:04:21PM +0800, Chao Yu <chao2.yu@samsung.com> wrote:
> >    openat(AT_FDCWD, "/cold1", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5
> >    fchdir(5)                               = 0
> >    getdents(5, /* 0 entries */, 32768)     = 0
> 
> I found an issue here.
> 
> If the dir entry of '/cold1/var' is removed from dentry page in '/cold1', at
> least we should return entries of '.' and '..' for the getdents invoking, but
> we didn't. So here it looks like we keep silent about some kind of error (i.e.
> ENOMEM/EIO...) when grabing&updating the dentry page of '/cold1', obviously
> it's better to report such error to user rather than ignoring it.

As for EIO, I would expect the kernel to log something. As for ENOMEM,
unless f2fs tries higher order or zone-specific allocations, that's
unlikely because the box had over 20GB memory free (according to top).

As for other errors, sure, could be.

Would that explain the sync lockup though?

> I'd like to send a patch to fix this issue, could you include the following
> patch in your f2fs module, so when it reproduces we can catch more details
> about this problem.

I can, but I guess you forgot to attach the patch.

On Fri, Nov 20, 2015 at 04:56:14AM +0800, Jaegeuk Kim <jaegeuk@kernel.org> wrote:
> > Ah, sorry if that might not have been clear - after a reboot, fsck showed
> > no errors and all files and directories (apparently) were there, i.e. it
> > looks like a transient problem, not a problem of the on-disk structure.
> 
> So, it seems that the system suffers from memory pressure significantly, which
> can incur ENOMEM, as I guess.
> Can you catch /sys/kernel/debug/f2fs/status at that moment?

If I can, I will - I didn't attempt to stress the filesystem since then, but
will presdumably start doing tests next week again.

-- 
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