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Subject: Re: [PATCH] ext4/xfs: add page refcount helper
To:     Jan Kara <jack@suse.cz>
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From:   Ralph Campbell <rcampbell@nvidia.com>
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On 10/7/20 1:25 AM, Jan Kara wrote:
> On Tue 06-10-20 16:09:30, Ralph Campbell wrote:
>> There are several places where ZONE_DEVICE struct pages assume a reference
>> count == 1 means the page is idle and free. Instead of open coding this,
>> add a helper function to hide this detail.
>>
>> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
>> Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> Looks as sane direction but if we are going to abstract checks when
> ZONE_DEVICE page is idle, we should also update e.g.
> mm/swap.c:put_devmap_managed_page() or
> mm/gup.c:__unpin_devmap_managed_user_page() (there may be more places like
> this but I found at least these two...). Maybe Dan has more thoughts about
> this.
> 
> 								Honza

I think this is a good point but I would like to make that a follow on
patch rather than add to this one.