Re: [PATCH] Do not print page type when the page has no type

[Petr Mladek <pmladek@suse.com>]

On Sun 2023-05-28 17:01:59, Hyeonggon Yoo wrote:
> On Sat, May 27, 2023 at 05:48:32PM +0100, Matthew Wilcox wrote:
> > It is confusing and unnecessary to print the page type when the
> > page has no type.
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > 
> > ---
> > 
> > I did not run the test-suite.  I'm in the middle of debugging something
> > else and this is an unwelcome distraction.  If this doesn't work quite
> > right, please fix it.
> 
> I ran the test suite, and a test case failed:
> 
> [    1.001641] test_printf: loaded.
> [    1.001736] test_printf: vsnprintf(buf, 256, "%pGt", ...) returned 41, expected 5
> [    1.001738] test_printf: vsnprintf(buf, 2, "%pGt", ...) returned 41, expected 5
> [    1.001738] test_printf: vsnprintf(buf, 0, "%pGt", ...) returned 41, expected 5
> [    1.001739] test_printf: kvasprintf(..., "%pGt", ...) returned '0xa(offline|guard|table|buddy|0xfffff875)', expected '0xa()'
> [    1.001774] test_printf: failed 4 out of 432 tests
> 
> The code mostly looks fine and the patch makes sense to me.
> But I'm not sure if it's a nice behavior to print garbage when it does not
> have a page type, although I can hardly imagine users of this flag other
> than __dump_page(). I'd rather keep printk part unchanged and add
> page_has_type() check in __dump_page().

I agree with Hyeonggon. The change in __dump_page() makes sense.
But vsprintf() should stay clever and do not print garbage.

Best Regards,
Petr