On Tue, May 19, 2020 at 09:35:59AM +0200, 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. > > > 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. I guess that you could Cc me in the reply. In that case, EROFS uses page->private as an atomic integer to trace 2 partial subpages in one page. I think that you could also use &page->private instead directly to replace &page_private(page) here since I didn't find some hint to pick &page_private(page) or &page->private. In addition, I found some limitation of new {attach,detach}_page_private helper (that is why I was interested in this series at that time [1] [2], but I gave up finally) since many patterns (not all) in EROFS are io_submit (origin, page locked): attach_page_private(page); ... put_page(page); end_io (page locked): SetPageUptodate(page); unlock_page(page); since the page is always locked, so io_submit could be simplified as set_page_private(page, ...); SetPagePrivate(page); , which can save both one temporary get_page(page) and one put_page(page) since it could be regarded as safe with page locked. btw, I noticed the patchset versions are PATCH [3], RFC PATCH [4], RFC PATCH v2 [5], RFC PATCH v3 [6], PATCH [7]. Although I also noticed the patchset title was once changed, but it could be some harder to trace the whole history discussion. [1] https://lore.kernel.org/linux-fsdevel/20200419051404.GA30986@hsiangkao-HP-ZHAN-66-Pro-G1/ [2] https://lore.kernel.org/linux-fsdevel/20200427025752.GA3979@hsiangkao-HP-ZHAN-66-Pro-G1/ [3] https://lore.kernel.org/linux-fsdevel/20200418225123.31850-1-guoqing.jiang@cloud.ionos.com/ [4] https://lore.kernel.org/linux-fsdevel/20200426214925.10970-1-guoqing.jiang@cloud.ionos.com/ [5] https://lore.kernel.org/linux-fsdevel/20200430214450.10662-1-guoqing.jiang@cloud.ionos.com/ [6] https://lore.kernel.org/linux-fsdevel/20200507214400.15785-1-guoqing.jiang@cloud.ionos.com/ [7] https://lore.kernel.org/linux-fsdevel/20200517214718.468-1-guoqing.jiang@cloud.ionos.com/ Thanks, Gao Xiang > > Thanks, > Guoqing > > >