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Date:   Wed, 06 May 2020 16:22:54 +0800
From:   "Huang\, Ying" <>
To:     Wei Yang <>
Cc:     Andrew Morton <>,
        <>, <>
Subject: Re: [PATCH 3/3] mm/swapfile.c: count won't be bigger than SWAP_MAP_MAX

Wei Yang <> 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 <> wrote:
>>> When the condition is true, there are two possibilities:
>>I'm struggling with this one.
>>>    1. count == SWAP_MAP_BAD
>>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  Where's that happening, or is the comment out of date?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

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