linux-ext4 - Re: [RFC 0/5] Ext4: Add support for blocksize < pagesize for dioread

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Message-Id: <20191104115936.C8F694C04A@d06av22.portsmouth.uk.ibm.com>
Date:   Mon, 4 Nov 2019 17:29:35 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     jack@...e.cz, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, mbobrowski@...browski.org
Subject: Re: [RFC 0/5] Ext4: Add support for blocksize < pagesize for
 dioread_nolock

On 11/4/19 4:13 PM, Ritesh Harjani wrote:
> 
> 
> On 11/4/19 12:46 AM, Theodore Y. Ts'o wrote:
>> On Tue, Oct 29, 2019 at 12:49:24PM +0530, Ritesh Harjani wrote:
>>>
>>> So it looks like these failed tests does not seem to be because of this
>>> patch series. But these are broken in general for at least 1K blocksize.
>>
>> Agreed, I failed to add them to the exclude list for diread_nolock_1k.
>> Thanks for pointing that out!
>>
>> After looking through these patches, it looks good.  So, I've landed
>> this series on the ext4 git tree.
>>
>> There are some potential conflicts with Matthew's DIO using imap patch
>> set.  I tried resolving them in the obvious way (see the tt/mb-dio
>> branch[1] on ext4.git), and unfortunately, there is a flaky test
>> failure with generic/270 --- 2 times out 30 runs of generic/270, the
>> file system is left inconsistent, with problems found in the block
>> allocation bitmap.
>>
>> [1] 
>> https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/log/?h=tt/mb-dio 
>>
>>
>> I've verified that generic/270 isn't a problem on -rc3, and it's not a
>> problem with just your patch series.  So, it's almost certain it's
>> because I screwed up the merge.  I applied each of Matthew's patch one
>> at a time, and conflict was in changes in ext4_end_io_dio, which is
>> dropped in Matthew's patch.  It wasn't obvious though where the
>> dioread-nolock-1k change should be applied in Matthew's patch series.
>> Could you take a look?  Thanks!!

Looked into the above mentioned branch.
I see the patches of iomap patch series were properly
applied. It is ok to completely remove function "ext4_end_io_dio" and
directly call for "ext4_convert_unwritten_extents" from 
"ext4_dio_write_end_io" (which is also done by default).

Actually io_end_vec in dioread_nolock series was used for AIO
DIO, since AIO+DIO was already using io_end structure and all
io_end usage was moved to use io_end_vec.
But since in iomap, we don't use io_end structure so it is ok
to directly call for ext4_convert_unwritten_extents with offset &
size argument.

hmm, I will try and run this generic/270 at my end to see what is going
wrong with this. It would be good if you could share the xfstest config
under which this is failing & if possible the failed logs/report.

Meanwhile, I will test generic/270 on your given branch with
dioread_nolock & 1K bs configuration.

-ritesh