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([2001:16b8:4852:3600:e80e:f5df:f780:7d57]) by smtp.gmail.com with ESMTPSA id by21sm283208ejb.93.2020.05.19.13.44.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 19 May 2020 13:44:42 -0700 (PDT) Subject: Re: [PATCH 10/10] mm/migrate.c: call detach_page_private to cleanup code From: Guoqing Jiang To: Andrew Morton Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, david@fromorbit.com, hch@infradead.org, willy@infradead.org References: <20200517214718.468-1-guoqing.jiang@cloud.ionos.com> <20200517214718.468-11-guoqing.jiang@cloud.ionos.com> <20200518221235.1fa32c38e5766113f78e3f0d@linux-foundation.org> Message-ID: <4b367950-bc52-af31-818e-2b668bf08409@cloud.ionos.com> Date: Tue, 19 May 2020 22:44:42 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Hi Andrew, On 5/19/20 9:35 AM, Guoqing Jiang wrote: > On 5/19/20 7:12 AM, Andrew Morton wrote: >> On Sun, 17 May 2020 23:47:18 +0200 Guoqing Jiang >> wrote: >> >>> We can cleanup code a little by call detach_page_private here. >>> >>> ... >>> >>> --- a/mm/migrate.c >>> +++ b/mm/migrate.c >>> @@ -804,10 +804,7 @@ static int __buffer_migrate_page(struct >>> address_space *mapping, >>>       if (rc != MIGRATEPAGE_SUCCESS) >>>           goto unlock_buffers; >>>   -    ClearPagePrivate(page); >>> -    set_page_private(newpage, page_private(page)); >>> -    set_page_private(page, 0); >>> -    put_page(page); >>> +    set_page_private(newpage, detach_page_private(page)); >>>       get_page(newpage); >>>         bh = head; >> mm/migrate.c: In function '__buffer_migrate_page': >> ./include/linux/mm_types.h:243:52: warning: assignment makes integer >> from pointer without a cast [-Wint-conversion] >>   #define set_page_private(page, v) ((page)->private = (v)) >>                                                      ^ >> mm/migrate.c:800:2: note: in expansion of macro 'set_page_private' >>    set_page_private(newpage, detach_page_private(page)); >>    ^~~~~~~~~~~~~~~~ >> >> The fact that set_page_private(detach_page_private()) generates a type >> mismatch warning seems deeply wrong, surely. >> >> Please let's get the types sorted out - either unsigned long or void *, >> not half-one and half-the other.  Whatever needs the least typecasting >> at callsites, I suggest. > > Sorry about that, I should notice the warning before. I will double > check if other > places need the typecast or not, then send a new version. Only this patch missed the typecast. I guess I just need to send an updated patch to replace this one (I am fine to send a new patch set if you want), sorry again for the trouble. > >> And can we please implement set_page_private() and page_private() with >> inlined C code?  There is no need for these to be macros. > > Just did a quick change. > > -#define page_private(page)             ((page)->private) > -#define set_page_private(page, v)      ((page)->private = (v)) > +static inline unsigned long page_private(struct page *page) > +{ > +       return page->private; > +} > + > +static inline void set_page_private(struct page *page, unsigned long > priv_data) > +{ > +       page->private = priv_data; > +} > > Then I get error like. > > fs/erofs/zdata.h: In function ‘z_erofs_onlinepage_index’: > fs/erofs/zdata.h:126:8: error: lvalue required as unary ‘&’ operand >   u.v = &page_private(page); >         ^ > > I guess it is better to keep page_private as macro, please correct me > in case I > missed something. Lost of problems need to be fixed if change page_private to inline function, so I think it is better to keep it and only convert set_page_private. mm/compaction.c: In function ‘isolate_migratepages_block’: ./include/linux/compiler.h:287:20: error: lvalue required as unary ‘&’ operand    __read_once_size(&(x), __u.__c, sizeof(x));  \                     ^ ./include/linux/compiler.h:293:22: note: in expansion of macro ‘__READ_ONCE’  #define READ_ONCE(x) __READ_ONCE(x, 1)                       ^~~~~~~~~~~ mm/internal.h:293:34: note: in expansion of macro ‘READ_ONCE’  #define page_order_unsafe(page)  READ_ONCE(page_private(page)) Thanks, Guoqing