Messages in this thread | | | Date | Tue, 20 Dec 2022 16:20:26 +0100 | From | Petr Mladek <> | Subject | Re: [RFC v3 3/4] mm, printk: introduce new format %pGt for page_type |
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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
> > :: > > %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>
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.
Otherwise the patch looks fine for the vsprinf side.
Best Regards, Petr
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