linux-kernel - Re: [PATCH] mm: kill frontswap

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Message-ID: <901409ed-504b-9500-54d8-e42f832e07b0@suse.cz>
Date:   Mon, 17 Jul 2023 16:31:42 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Johannes Weiner <hannes@...xchg.org>,
        Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Yosry Ahmed <yosryahmed@...gle.com>,
        Christoph Hellwig <hch@...radead.org>,
        Nhat Pham <nphamcs@...il.com>,
        Domenico Cerasuolo <cerasuolodomenico@...il.com>,
        konrad.wilk@...cle.com, vitaly.wool@...sulko.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: kill frontswap

On 7/17/23 16:12, Johannes Weiner wrote:
> On Sat, Jul 15, 2023 at 04:42:13AM +0100, Matthew Wilcox wrote:
>> On Fri, Jul 14, 2023 at 03:46:08PM -0400, Johannes Weiner wrote:
>> > diff --git a/mm/zswap.c b/mm/zswap.c
>> > index 62195f72bf56..1b0128060792 100644
>> > --- a/mm/zswap.c
>> > +++ b/mm/zswap.c
>> > @@ -2,7 +2,7 @@
>> >  /*
>> >   * zswap.c - zswap driver file
>> >   *
>> > - * zswap is a backend for frontswap that takes pages that are in the process
>> > + * zswap is a cache that takes pages that are in the process
>> >   * of being swapped out and attempts to compress and store them in a
>> >   * RAM-based memory pool.  This can result in a significant I/O reduction on
>> >   * the swap device and, in the case where decompressing from RAM is faster
>> > @@ -20,7 +20,6 @@
>> >  #include <linux/spinlock.h>
>> >  #include <linux/types.h>
>> >  #include <linux/atomic.h>
>> > -#include <linux/frontswap.h>
>> >  #include <linux/rbtree.h>
>> >  #include <linux/swap.h>
>> >  #include <linux/crypto.h>
>> 
>> To make this patch compile, I had to add zswap.h to the include list.
> 
> I can fix that up, but I'm curious what kind of failure you saw. It
> built fine for me, not even a warning.

I get warnings but only with W=1 (worth fixing up though).

  CC      mm/zswap.o
mm/zswap.c:1203:6: warning: no previous prototype for ‘zswap_store’ [-Wmissing-prototypes]
 1203 | bool zswap_store(struct page *page)
      |      ^~~~~~~~~~~
mm/zswap.c:1382:6: warning: no previous prototype for ‘zswap_load’ [-Wmissing-prototypes]
 1382 | bool zswap_load(struct page *page)
      |      ^~~~~~~~~~
mm/zswap.c:1470:6: warning: no previous prototype for ‘zswap_invalidate’ [-Wmissing-prototypes]
 1470 | void zswap_invalidate(int type, pgoff_t offset)
      |      ^~~~~~~~~~~~~~~~
mm/zswap.c:1487:6: warning: no previous prototype for ‘zswap_swapon’ [-Wmissing-prototypes]
 1487 | void zswap_swapon(int type)
      |      ^~~~~~~~~~~~
mm/zswap.c:1502:6: warning: no previous prototype for ‘zswap_swapoff’ [-Wmissing-prototypes]
 1502 | void zswap_swapoff(int type)
      |      ^~~~~~~~~~~~~