Messages in this thread | | | Subject | Re: [PATCH 10/10] mm/migrate.c: call detach_page_private to cleanup code | From | Guoqing Jiang <> | Date | Tue, 19 May 2020 13:02:26 +0200 |
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On 5/19/20 12:06 PM, Gao Xiang wrote: > 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 <guoqing.jiang@cloud.ionos.com> 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.
Sorry for not do that ...
> 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.
Thanks for the input, I just did a quick test, so need to investigate more. And I think it is better to have another thread to change those macros to inline function, then fix related issues due to the change.
> 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.
The SetPageUptodate is not called inside {attach,detach}_page_private, I could probably misunderstand your point, maybe you want the new pairs can handle the locked page, care to elaborate more?
> 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/
All the cover letter of those series are here.
RFC V3:https://lore.kernel.org/lkml/20200507214400.15785-1-guoqing.jiang@cloud.ionos.com/ RFC V2:https://lore.kernel.org/lkml/20200430214450.10662-1-guoqing.jiang@cloud.ionos.com/ RFC:https://lore.kernel.org/lkml/20200426214925.10970-1-guoqing.jiang@cloud.ionos.com/
And the latest one:
https://lore.kernel.org/lkml/20200430214450.10662-1-guoqing.jiang@cloud.ionos.com/
Thanks, Guoqing
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