From: Dan Streetman <ddstreet@ieee.org>
To: Weijie Yang <weijie.yang.kh@gmail.com>
Cc: Seth Jennings <sjennings@variantweb.net>,
linux-mm@kvack.org, linux-kernel <linux-kernel@vger.kernel.org>,
Bob Liu <bob.liu@oracle.com>, Minchan Kim <minchan@kernel.org>,
Weijie Yang <weijie.yang@samsung.com>
Subject: Re: [PATCH] mm/zswap: don't allow entry eviction if in use by load
Date: Thu, 21 Nov 2013 17:18:21 -0500 [thread overview]
Message-ID: <CALZtONDH1naq7uKOfcqCz+5bREYYd3A5-DN72wJ5TOpZEcaygw@mail.gmail.com> (raw)
In-Reply-To: <CALZtONByWEv-vyx8+HMn+o53hPO4L_UY-+BbLRrBoWx-u2UejA@mail.gmail.com>
On Thu, Nov 21, 2013 at 4:44 PM, Dan Streetman <ddstreet@ieee.org> wrote:
> On Wed, Nov 20, 2013 at 8:59 PM, Weijie Yang <weijie.yang.kh@gmail.com> wrote:
>> Hello Dan
>>
>> On Thu, Nov 21, 2013 at 3:48 AM, Dan Streetman <ddstreet@ieee.org> wrote:
>>> The changes in commit 0ab0abcf511545d1fddbe72a36b3ca73388ac937
>>> introduce a bug in writeback, if an entry is in use by load
>>> it will be evicted anyway, which isn't correct (technically,
>>> the code currently in zbud doesn't actually care much what the
>>> zswap evict function returns, but that could change).
>>
>> Thanks for your work. Howerver it is not a bug.
>>
>> I have thought about this situation, and it will never happen.
>> If entry is being loaded, its corresponding page must be in swapcache
>> so zswap_get_swap_cache_page() will return ZSWAP_SWAPCACHE_EXIST
>
>
> Can I also ask why you do a rb_search instead of just checking the
> entry->refcount? Doing the search is going to take longer than just
> checking the refcount; is there some case where the entry will not be
> in the rb but will have a nonzero refcount?
Never mind; I realized the entry will have been free'd once it's
refcount is 0 so that can't be checked.
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prev parent reply other threads:[~2013-11-21 22:18 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-20 19:48 Dan Streetman
2013-11-21 1:59 ` Weijie Yang
2013-11-21 21:44 ` Dan Streetman
2013-11-21 22:18 ` Dan Streetman [this message]
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