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Date:   Mon, 8 Apr 2019 10:26:17 -0700 (PDT)
From:   Hugh Dickins <hughd@google.com>
To:     Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
cc:     Hugh Dickins <hughd@google.com>,
        "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>,
        Vineeth Pillai <vpillai@digitalocean.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kelley Nielsen <kelleynnn@gmail.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Rik van Riel <riel@surriel.com>,
        Huang Ying <ying.huang@intel.com>,
        Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: shmem_recalc_inode: unable to handle kernel NULL pointer
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On Mon, 8 Apr 2019, Konstantin Khlebnikov wrote:
> 
> I suppose your solution will wait for wakeup from shmem_evict_inode()?

No, it's the other way round: shmem_unuse() gets on with its work without
delay, shmem_evict_inode() waits until the stop_eviction count has gone
down to zero, saying nobody else is at work on the inode.

Waiting in shmem_evict_inode() might be more worrying, if it weren't
already packed full with lock_page()s. And less attractive with the old
quadratic style of swapoff, when shmem_evict_inode() would have freed
the inode's swap much more efficiently than swapoff could then manage.

Hugh