On Tue, Dec 20, 2022 at 04:20:26PM +0100, Petr Mladek wrote: > On Sun 2022-12-18 19:19:00, Hyeonggon Yoo wrote: > > %pGp format is used to print 'flags' field of struct page. > > As some page flags (e.g. PG_buddy, see page-flags.h for more details) > > are set in page_type field, introduce %pGt format which provides > > human readable output of page_type. > > > > Note that the sense of bits are different in page_type. if page_type is > > 0xffffffff, no flags are set. if PG_slab (0x00100000) flag is set, > > page_type is 0xffefffff. Clearing a bit means we set the bit. > > > > Bits in page_type are inverted when printing page type names. > > > > --- a/Documentation/core-api/printk-formats.rst > > +++ b/Documentation/core-api/printk-formats.rst > > @@ -575,12 +575,13 @@ The field width is passed by value, the bitmap is passed by reference. > > Helper macros cpumask_pr_args() and nodemask_pr_args() are available to ease > > printing cpumask and nodemask. > > > > -Flags bitfields such as page flags, gfp_flags > > +Flags bitfields such as page flags, page_type, gfp_flags > > --------------------------------------------- > > Please, underline the entire title. Otherwise, "make htmldoc" > complains ;-) > > /prace/kernel/linux/Documentation/core-api/printk-formats.rst:579: WARNING: Title underline too short. > Flags bitfields such as page flags, page_type, gfp_flags Still not getting used to rst format ;) Will fix, thanks! > > > > > > :: > > > > %pGp 0x17ffffc0002036(referenced|uptodate|lru|active|private|node=0|zone=2|lastcpupid=0x1fffff) > > + %pGt 0xffefffff(slab) > > %pGg GFP_USER|GFP_DMA32|GFP_NOWARN > > %pGv read|exec|mayread|maywrite|mayexec|denywrite > > > > Please, explain this also in the paragraph below these examples. > I would personally refactor it to an itemized list, something like: > > <proposal> > For printing flags bitfields as a collection of symbolic constants that > would construct the value. The type of flags is given by the third > character. Currently supported are: > > - p - [p]age flags, expects value of type (``unsigned long *``) > - t - page [t]ype, expects value of type (``unsigned int *``) > - v - [v]ma_flags, expects value of type (``unsigned long *``) > - g - [g]fp_flags, expects value of type (``gfp_t *``) > > The flag names and print order depends on the particular type. > </proposal> The proposal sounds reasonable to me, will adjust in next version. > Rant: > Sigh, it looks a bit error prone when similar pointer modifiers > expects pointers to different types. I wish there was a way how > to check the passed pointer type at compilation time. But it > is generic problem with these %p* modifiers. >From my limited knowledge, it seems that there is no way to check this :/ > > Otherwise the patch looks fine for the vsprinf side. Thank you for looking at this! > > Best Regards, > Petr -- Thanks, Hyeonggon
