Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Message-ID: <9c475803276ea2b32cadc8f72d397c180475d0cc.camel@perches.com>
Subject: Re: [PATCH v2 3/3] vsprintf: dump full information of page flags in
 pGp
From:   Joe Perches <joe@perches.com>
To:     Matthew Wilcox <willy@infradead.org>,
        Yafang Shao <laoar.shao@gmail.com>
Cc:     andriy.shevchenko@linux.intel.com, david@redhat.com,
        vbabka@suse.cz, linmiaohe@huawei.com, cl@linux.com,
        penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com,
        akpm@linux-foundation.org, pmladek@suse.com, rostedt@goodmis.org,
        sergey.senozhatsky@gmail.com, linux@rasmusvillemoes.dk,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Date:   Mon, 01 Feb 2021 10:51:03 -0800
In-Reply-To: <20210201141505.GR308988@casper.infradead.org>
References: <20210201115610.87808-1-laoar.shao@gmail.com>
         <20210201115610.87808-4-laoar.shao@gmail.com>
         <20210201141505.GR308988@casper.infradead.org>
Content-Type: text/plain; charset="ISO-8859-1"
User-Agent: Evolution 3.38.1-1 
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Mon, 2021-02-01 at 14:15 +0000, Matthew Wilcox wrote:
> On Mon, Feb 01, 2021 at 07:56:10PM +0800, Yafang Shao wrote:
> > - Before the patch,
> > [ 6343.396602] Slab 0x000000004382e02b objects=33 used=3 fp=0x000000009ae06ffc flags=0x17ffffc0010200(slab|head)
> > 
> > - After the patch,
> > [ 6871.296131] Slab 0x00000000c0e19a37 objects=33 used=3 fp=0x00000000c4902159 flags=0x17ffffc0010200(Node 0,Zone 2,Lastcpupid 0x1fffff,slab|head)
> 
> I would suggest it will be easier to parse as:
> 
> flags=0x17ffffc0010200(slab|head|node=0|zone=2|lastcpupid=0x1fffff)
> 
> That should alleviate the concerns about debugfs format change -- we've
> never guaranteed that flag names won't change, and they now look enough
> like flags that parsers shouldn't fall over them.

Seems sensible and would make the generating code simpler too.

But is it worth the vsprintf code expansion for the 5 current uses?

mm/debug.c:     pr_warn("%sflags: %#lx(%pGp)%s\n", type, head->flags, &head->flags,
mm/memory-failure.c:                    pr_info("soft offline: %#lx: %s migration failed %d, type %lx (%pGp)\n",
mm/memory-failure.c:            pr_info("soft offline: %#lx: %s isolation failed, page count %d, type %lx (%pGp)\n",
mm/memory-failure.c:            pr_info("%s: %#lx: unknown page type: %lx (%pGp)\n",
mm/page_owner.c:                        "PFN %lu type %s Block %lu type %s Flags %#lx(%pGp)\n",

Wouldn't it be more sensible just to put this code in a new function
call in mm?