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Sender: Minchan Kim <minchan.kim@gmail.com>
Date:   Thu, 30 Mar 2023 18:42:38 -0700
From:   Minchan Kim <minchan@kernel.org>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Pankaj Raghav <p.raghav@samsung.com>, martin@omnibond.com,
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Subject: Re: [PATCH 1/5] zram: remove the call to page_endio in the bio
 end_io handler
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On Thu, Mar 30, 2023 at 04:16:25PM -0700, Christoph Hellwig wrote:
> On Thu, Mar 30, 2023 at 03:51:54PM -0700, Minchan Kim wrote:
> > > to remove the call to page_endio() function that unlocks or marks
> > > writeback end on the page.
> > > 
> > > Rename the endio handler from zram_page_end_io to zram_read_end_io as
> > > the call to page_endio() is removed and to associate the callback to the
> > > operation it is used in.
> > 
> > Since zram removed the rw_page and IO comes with bio from now on,
> > IIUC, we are fine since every IO will go with chained-IO. Right?
> 
> writeback_store callszram_bvec_read with a NULL bio, that is it just
> fires off an async read without any synchronization.

It should go under zram_read_from_zspool, not zram_bvec_read_from_bdev.
The ZRAM_UNDER_WB and ZRAM_WB under zram_slot_lock should synchronize.