Re: f2fs_bug_on in init_dirty_segmap

[Philippe De Muyter <phdm@macq.eu>]

On Fri, Mar 10, 2017 at 10:20:34AM -0800, Jaegeuk Kim wrote:
> On 03/10, Philippe De Muyter wrote:
> ...
> > > > It is actually a Freescale (now NXP) provided kernel tagged rel_imx_4.1.15_1.2.0_ga
> > > > available at git://git.freescale.com/imx/linux-2.6-imx.git 
> > > > 
> > > > I surmise that the f2fs driver is the one from the linux-4.1 version.
> > > > 
> > > > > 
> > > > > You can get the latest f2fs-tools from
> > > > > http://git.kernel.org/cgit/linux/kernel/git/jaegeuk/f2fs-tools.git/log/?h=dev-test
> > > > > 
> > > > > Anyway, if you don't have time, you may have some options like:
> > > > > 
> > > > > 1. disable F2FS_CHECK_FS in Kconfig
> > > > >  : bypass BUG_ON here, so mount-ro would be preferable.
> > > > 
> > > > Actually F2FS_CHECK_FS was disabled, but kernel panic'ed.
> > > 
> > > So, you got a warning message from there?
> > > 
> > > #ifdef CONFIG_F2FS_CHECK_FS
> > > #define f2fs_bug_on(sbi, condition)	BUG_ON(condition)
> > > #define f2fs_down_write(x, y)	down_write_nest_lock(x, y)
> > > #else
> > > #define f2fs_bug_on(sbi, condition)					\
> > > 	do {								\
> > > 		if (unlikely(condition)) {				\
> > > 			WARN_ON(1);					\
> > > 			set_sbi_flag(sbi, SBI_NEED_FSCK);		\
> > > 		}							\
> > > 	} while (0)
> > > #define f2fs_down_write(x, y)	down_write(x)
> > > #endif
> > 
> > Yes, I got a 'panic'.  I'll look deeper into that and let you know.
> 
> Okay, thank you. ;)

For a test, I forced a call to f2fs_bug_on(sbi, 1) at the entry of init_dirty_segmap(),
and tested on another board but only got a message, not a panic, so I don't know
what happened on the first board.  If it happens again on another board, I'll
try to collect more info.

> 
> > > > > 2. run fsck.f2fs
> > > > >  : fix some inconsistency and let you mount your system again.
> > > > > 
> > > > > So, I think you'd better try #1 to retrieve your important data, and then
> > > > > #2 to fix something wrong.
> > > > 
> > > > There wasn't a need to retrieve important data, as it is an unattended device
> > > > in the wild.  The problem was that boot did not succeed anymore and the device
> > > > needed a return to our aftersales department for reflashing.  Without the 'panic',
> > > > and with a read-only mount we could probably fix it without reflashing
> > > > and without return.
> > > 
> > > So, there is no fscking before mounting any filesystem during boot-up, right?
> > > Most of distros and android do that and provide a recovery mode tho.
> > 
> > No, there is no fsck before mounting the root filesystem during boot-up.
> > But I do my best to avoid writing in the root partition.  It's not read-only,
> > but all log, lock, run, cache and tmp files are in tmpfs partitions.  I have
> > just noticed though that the partition is mounted with 'relatime', not 'noatime'
> > as I would like, but I do not know where this 'relatime' option comes from.
> > Is 'relatime' a default mount option for f2fs ?
> 
> Not specific from f2fs. It's default given by vfs, and you need to mount with
> noatime explicitly, if you want. BTW, once you got a panic during boot-up, how
> can you change mount option?

It is a ARM board, started by U-boot.  I can change the kernel command-line,
and hope the kernel will understand the noatime option.

I wasn't speaking about changing the mount option after a panic, but about changing
the default mount option on all the new boards, to avoid unvoluntary writes to the
eMMC.

> 
> Thanks,
> 
> > 
> > > 
> > > I think there is a way to mount with ro without loading in-memory structures
> > > which results in potential panics. Will cosider about that. ;)
> > > 
> > > Note, there is a backported f2fs for v4.1 which I've been maintaining.
> > > 
> > > http://git.kernel.org/cgit/linux/kernel/git/jaegeuk/f2fs-stable.git/log/?h=linux-4.1.y
> > 
> > Thank you. I will apply it
> > 
> > Philippe

-- 
Philippe De Muyter +32 2 6101532 Macq SA rue de l'Aeronef 2 B-1140 Bruxelles

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