linux-ext4 - RE: AW: AW: ext4 filesystem bad extent error review

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Date:	Mon, 6 Jan 2014 13:45:49 +0800
From:	"Huang Weller (CM/ESW12-CN)" <Weller.Huang@...bosch.com>
To:	"Juergens Dirk (CM-AI/ECO2)" <Dirk.Juergens@...bosch.com>,
	Eric Sandeen <sandeen@...hat.com>,
	Theodore Ts'o <tytso@....edu>
CC:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: RE: AW: AW: ext4 filesystem bad extent error review

> On Thu, Jan 03, 2014 at 19:49, Eric Sandeen wrote
> >
> > On 1/3/14, 12:45 PM, Juergens Dirk (CM-AI/ECO2) wrote:
> > >
> > > On Thu, Jan 03, 2014 at 19:24, Eric Sandeen wrote
> > >>
> > >> On 1/3/14, 10:29 AM, Juergens Dirk (CM-AI/ECO2) wrote:
> > >>> So, I think there _might_ be a kernel bug, but it could be also a
> > >> problem
> > >>> related to the particular type of eMMC. We did not observe the same
> > >> issue
> > >>> in previous tests with another type of eMMC from another supplier,
> > >> but this
> > >>> was with an older kernel patch level and with another HW design.
> > >>>
> > >>> Regarding a possible kernel bug: Is there any chance that the
> > invalid
> > >>> ee_len or ee_start are returned by, e.g., the block allocator ?
> > >>> If so, can we try to instrument the code to get suitable traces ?
> > >>> Just to see or to exclude that the corrupted inode is really
> > written
> > >>> to the eMMC ?
> > >>
> > >> From your description it does sound possible that it's a kernel bug.
> > >> Adding testcases to the code to catch it before it hits the journal
> > >> might be helpful - but then maybe this is something getting
> > overwritten
> > >> after the fact - hard to say.
> > >>
> > >> Can you share more details of the test you are running?  Or maybe
> > even
> > >> the test itself?
> > >
> > > Yes, for sure, we can. Weller, please provide additional details
> > > or corrections.
> > >
> > > In short:
> > > Basically we use an automated cyclic test writing many small
> > > (some kBytes) files with CRC checksums for easy consistency check
> > > into a separate test partition. Files also contain meta information
> > > like filename,  sequence number and a random number to allow to
> > identify
> > > from block device image dumps, if we just see a fragment of an old
> > > deleted file or a still valid one.
> > >
> > > Each test loop looks like this:
> >
> > 0) mkfs the filesystem - with what options?  How big?
> 
> Here we do need the details from Weller, cause
> he has done all this.

We use the default options with option nodiscard:
mkfs.ext4 -E nodiscard /dev/$PAR
the size is about 6G.

> >
> > > 1) Boot the device after power on or reset
> > > 2) Do fsck -n BEFORE mounting
> > > 2 a) (optional) binary dump of the journal
> > > 3) Mount test partition
> >
> > Again with what options, if any?
> 
> Details again have to be given by Weller, sorry.

Mount options:
-ext4 default options: rw,relatime,data=ordered,barrier=1
-rw,relatime,data=ordered,barrier=1,journal_checksum
And the test partition size is about 6G. But I filled the test partition and make there is only 700M empty space left.


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