Date:	Fri, 26 Sep 2014 23:52:14 +0200
From:	Joachim Eastwood <manabian@...il.com>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [git pull] vfs fixes

On 26 September 2014 23:28, Joachim  Eastwood <manabian@...il.com> wrote:
> On 26 September 2014 22:58, Al Viro <viro@...iv.linux.org.uk> wrote:
>> On Fri, Sep 26, 2014 at 10:46:14PM +0200, Joachim Eastwood wrote:
>>> On 14 September 2014 21:47, Al Viro <viro@...iv.linux.org.uk> wrote:
>>> > double iput() on failure exit in lustre, racy removal of spliced dentries
>>> > from ->s_anon in __d_materialise_dentry() plus a bunch of assorted RCU pathwalk
>>> > fixes.  Please, pull from the usual place -
>>> > git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git for-linus
>>> >
>>> > Shortlog:
>>> > Al Viro (5):
>>> >       [fix] lustre: d_make_root() does iput() on dentry allocation failure
>>> >       move the call of __d_drop(anon) into __d_materialise_unique(dentry, anon)
>>> >       fix bogus read_seqretry() checks introduced in b37199e
>>> >       don't bugger nd->seq on set_root_rcu() from follow_dotdot_rcu()
>>> >       be careful with nd->inode in path_init() and follow_dotdot_rcu()
>>>
>>> Hi,
>>>
>>> Commit 4023bfc9f351a7994 "be careful with nd->inode in path_init() and
>>> follow_dotdot_rcu(), seem to hang my ARM no-MMU platform when mounting
>>> the ramdisk.
>>>
>>> 3.17-rc4 - works
>>> 3.17-rc5 - works with 4023bfc9f351a7994 reverted.
>>>
>>> Boot log with from rc5:
>>> [ 5.810000] TCP: cubic registered
>>> [ 5.820000] NET: Registered protocol family 17
>>> [ 5.860000] lpc2k-rtc 40046000.rtc: hctosys: unable to read the hardware clock
>>> [ 5.910000] mmc_host mmc0: Bus speed (slot 0) = 12000000Hz (slot req
>>> 25000000Hz, actual 12000000HZ div = 0)
>>> [ 5.930000] mmc0: new SDHC card at address 0007
>>> [ 5.950000] mmcblk0: mmc0:0007 SD08G 7.42 GiB
>>> [ 6.150000] clk: Not disabling unused clocks
>>> [ 81.240000] random: nonblocking pool is initialized
>>>
>>> And there it just hangs it seems.
>>>
>>>
>>> With patch reverted
>>> [ 5.810000] TCP: cubic registered
>>> [ 5.820000] NET: Registered protocol family 17
>>> [ 5.850000] lpc2k-rtc 40046000.rtc: hctosys: unable to read the hardware clock
>>> [ 6.100000] clk: Not disabling unused clocks
>>> [ 6.110000] RAMDISK: gzip image found at block 0
>>> [ 9.590000] VFS: Mounted root (ext2 filesystem) readonly on device 1:0.
>>> [ 9.600000] devtmpfs: mounted
>>> [ 9.610000] Freeing unused kernel memory: 68K (281e5000 - 281f6000)
>>>
>>> And then user space starts.
>>
>> *blink*  What happens to mmc-related messages on successful boot?  And what
>> in that commit could've possibly lead to those not being produced?
>
> Now I am puzzled too. I can not longer reproduce that hang.
>
> I am guessing it was probably related to the mmc card being flaky or
> something random like that.
>
> Sorry for noise!

Just to confirm what was happening:

I managed to trigger it again and removing the mmc driver makes the
problem go away. So this is an mmc issue and _not_ vfs.

But what is strange is that reverting 4023bfc9f351a also makes it boot
again... Which is what fooled me.

Here are the boot logs just in case you want to have a look.
Boot log with hang: http://slexy.org/raw/s2eRhKN3aG
Boot ok (4023bfc9f351a reverted): http://slexy.org/raw/s21NgzZkCA

mmc is behaving differently.

Sorry for prematurely blaming vfs.

regards,
Joachim Eastwood
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