linux-ext4 - Re: [RFCv3 02/10] libfs: Add __generic_file_fsync

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Date:   Mon, 17 Apr 2023 15:31:53 +0530
From:   Ritesh Harjani (IBM) <ritesh.list@...il.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@...radead.org>,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        "Darrick J . Wong" <djwong@...nel.org>,
        Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
        Disha Goel <disgoel@...ux.ibm.com>
Subject: Re: [RFCv3 02/10] libfs: Add __generic_file_fsync_nolock implementation

Jan Kara <jack@...e.cz> writes:

> On Fri 14-04-23 19:59:42, Ritesh Harjani wrote:
>> Jan Kara <jack@...e.cz> writes:
>>
>> > On Fri 14-04-23 06:12:00, Christoph Hellwig wrote:
>> >> On Fri, Apr 14, 2023 at 02:51:48PM +0200, Jan Kara wrote:
>> >> > On Thu 13-04-23 22:59:24, Christoph Hellwig wrote:
>> >> > > Still no fan of the naming and placement here.  This is specific
>> >> > > to the fs/buffer.c infrastructure.
>> >> >
>> >> > I'm fine with moving generic_file_fsync() & friends to fs/buffer.c and
>> >> > creating the new function there if it makes you happier. But I think
>> >> > function names should be consistent (hence the new function would be named
>> >> > __generic_file_fsync_nolock()). I agree the name is not ideal and would use
>> >> > cleanup (along with transitioning everybody to not take i_rwsem) but I
>> >> > don't want to complicate this series by touching 13+ callsites of
>> >> > generic_file_fsync() and __generic_file_fsync(). That's for a separate
>> >> > series.
>> >>
>> >> I would not change the existing function.  Just do the right thing for
>> >> the new helper and slowly migrate over without complicating this series.
>> >
>> > OK, I can live with that temporary naming inconsistency I guess. So
>> > the function will be __buffer_file_fsync()?
>>
>> This name was suggested before, so if that's ok I will go with this -
>> "generic_buffer_fsync()". It's definition will lie in fs/buffer.c and
>> it's declaration in include/linux/buffer_head.h
>>
>> Is that ok?
>
> Yes, that is fine by me. And I suppose this variant will also issue the
> cache flush, won't it?

No. We don't issue cache flush (REQ_PREFLUSH) in generic_buffer_fsync(),
neither __generic_file_fsync() does that.

> But then we also need __generic_buffer_fsync()
> without issuing the cache flush for ext4 (we need to sync parent before
> issuing a cache flush) and FAT.

Yes, we do take care of that by -

<simplified logic>
ret = generic_buffer_fsync()
if (!ret)
   ret = ext4_sync_parent(inode)
if (test_opt(inode->i_sb, BARRIER))
   blkdev_issue_flush()

Am I missing anything. I have sent a [v5] with all of the comments
addressed. Could you please take a look and let me know if it looks
good or is there anything required?

[v5]: https://lore.kernel.org/linux-ext4/cover.1681639164.git.ritesh.list@gmail.com/T/#t

-ritesh