linux-kernel - Re: [PATCH -V2 4/5] swap: remove get/put_swap_device() in __swap

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Message-ID: <9cbd93e0-721a-01c2-14dd-87f89363a830@redhat.com>
Date:   Mon, 22 May 2023 14:06:05 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Huang Ying <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Hugh Dickins <hughd@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        Minchan Kim <minchan@...nel.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>, Yu Zhao <yuzhao@...gle.com>
Subject: Re: [PATCH -V2 4/5] swap: remove get/put_swap_device() in
 __swap_duplicate()

On 22.05.23 09:09, Huang Ying wrote:
> __swap_duplicate() is called by
> 
> - swap_shmem_alloc(): the page lock of the swap cache is held.

page lock of the swap cache? Did you really mean to say that or am I 
confused?

"Page lock of the page that is in the swap cache?"

> 
> - copy_nonpresent_pte() -> swap_duplicate() and try_to_unmap_one() ->
>    swap_duplicate(): the page table lock is held.
> 
> - __read_swap_cache_async() -> swapcache_prepare(): enclosed with
>    get/put_swap_device() in __read_swap_cache_async() already.
> 
> So, it's safe to remove get/put_swap_device() in __swap_duplicate().



-- 
Thanks,

David / dhildenb