From: "Huang\, Ying" <ying.huang@intel.com>
To: Wei Yang <richard.weiyang@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: [PATCH 3/3] mm/swapfile.c: count won't be bigger than SWAP_MAP_MAX
Date: Wed, 06 May 2020 16:22:54 +0800 [thread overview]
Message-ID: <87k11pv5ep.fsf@yhuang-dev.intel.com> (raw)
In-Reply-To: <20200502132911.u6y6hkh56ik4ojne@master> (Wei Yang's message of "Sat, 2 May 2020 13:29:11 +0000")
Wei Yang <richard.weiyang@gmail.com> writes:
> On Fri, May 01, 2020 at 03:48:53PM -0700, Andrew Morton wrote:
>>On Fri, 1 May 2020 01:52:59 +0000 Wei Yang <richard.weiyang@gmail.com> wrote:
>>
>>> When the condition is true, there are two possibilities:
>>
>>I'm struggling with this one.
>>
>>> 1. count == SWAP_MAP_BAD
>>> 2. count == (SWAP_MAP_MAX & COUNT_CONTINUED) == SWAP_MAP_SHMEM
>>
>>I'm not sure what 2. is trying to say. For a start, (SWAP_MAP_MAX &
>>COUNT_CONTINUED) is zero. I guess it meant "|"?
>
> Oops, you are right. It should be (SWAP_MAP_MAX | COUNT_CONTINUED).
>
> Sorry for the confusion.
>
>>
>>Also, the return value documentation says we return EINVAL for migration
>>entries. Where's that happening, or is the comment out of date?
>>
>
> Not paid attention to this.
>
> Take look into the code, I don't find a relationship between the swap count
> and migration. Seems we just make a migration entry but not duplicate it.
> If my understanding is correct.
Per my understanding, one functionality of the error path is to catch
the behavior that shouldn't happen at all. For example, if
__swap_duplicate() is called for the migration entry because of some
race condition.
Best Regards,
Huang, Ying
next prev parent reply other threads:[~2020-05-06 8:23 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-01 1:52 [PATCH 1/3] mm/swapfile.c: classify SWAP_MAP_XXX to make it more readable Wei Yang
2020-05-01 1:52 ` [PATCH 2/3] mm/swapfile.c: __swap_entry_free() always free 1 entry Wei Yang
2020-05-01 1:52 ` [PATCH 3/3] mm/swapfile.c: count won't be bigger than SWAP_MAP_MAX Wei Yang
2020-05-01 22:48 ` Andrew Morton
2020-05-02 13:29 ` Wei Yang
2020-05-02 13:41 ` Wei Yang
2020-05-06 8:22 ` Huang, Ying [this message]
2020-05-07 22:20 ` Wei Yang
2020-05-07 23:48 ` Huang, Ying
2020-05-08 21:19 ` Wei Yang
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