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Re: [PATCH] lib/vsprintf.c: increase the size of the field_width variable

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Hello, Joe.

On Thu, Sep 10, 2015 at 08:41:25AM -0700, Joe Perches wrote:
> On Thu, 2015-09-10 at 10:36 -0400, Tejun Heo wrote:
> > On Wed, Sep 09, 2015 at 12:26:39PM -0700, Joe Perches wrote:
> > > > > %*pb is meant for smallish bitmaps, not big ones.
> []
> > The use case isn't from me, but why not?
> 
> Imagine the output of the 500k bitmap if every other
> bit is set.

Yeah, but the caller still should be able to call, say, scnprintf()
with a limited buffer and get the output till the end of the buffer
along with the indication that the output has been truncated.

> %*pb isn't capable of multiple line output and
> seq_printf output would also fail as it uses k.alloc
> memory not vmalloc.

Heh, and it should fail.

> I think that a more limited mechanism might be to use a
> multiple line oriented function like print_hex_debug
> and not try to emit the entire thing in a single go.

I'm not that worried about the berserk cases which try to print a
really long output on consoles but the subtle failure modes are
worrying.

> > Why are we even copying the struct on invocations?
> > Only some functions modify the values after all.
> > We might as well pass around pointer to the struct
> > and let the callees wihch modify them copy the
> > fields in local vars like normal functions.
> 
> You are of course welcome and able to change it.
> 
> btw: the current implementation has a limitation
> on 32 bit arches as it uses an int argument for the
> unsigned long count of bits in a bitmap.
> 
> That's a bitmap that should not be printed anyway.

That's 256Mbytes of bitmap.  I don't think we need to worry about that
at the moment.

Thanks.

-- 
tejun
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[PATCH] lib/vsprintf.c: increase the size of the field_width variable Maurizio Lombardi <mlombard@redhat.com> - 2015-09-09 12:20 +0200
  Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Tejun Heo <tj@kernel.org> - 2015-09-09 15:40 +0200
  Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Joe Perches <joe@perches.com> - 2015-09-09 18:40 +0200
    Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Tejun Heo <tj@kernel.org> - 2015-09-09 18:40 +0200
      Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Joe Perches <joe@perches.com> - 2015-09-09 19:00 +0200
    Re: [PATCH] lib/vsprintf.c: increase the size of the field_width variable Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-09-09 21:00 +0200
      Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Joe Perches <joe@perches.com> - 2015-09-09 21:30 +0200
        Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Tejun Heo <tj@kernel.org> - 2015-09-10 16:40 +0200
          Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Joe Perches <joe@perches.com> - 2015-09-10 17:50 +0200
            Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Tejun Heo <tj@kernel.org> - 2015-09-10 17:50 +0200
      Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Maurizio Lombardi <mlombard@redhat.com> - 2015-09-10 09:10 +0200
        Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Maurizio Lombardi <mlombard@redhat.com> - 2015-09-10 09:20 +0200
        Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Joe Perches <joe@perches.com> - 2015-09-10 09:40 +0200
          Re: [PATCH] lib/vsprintf.c: increase the size of the field_width variable Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-09-10 10:00 +0200
            Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Joe Perches <joe@perches.com> - 2015-09-10 10:20 +0200
              Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Tejun Heo <tj@kernel.org> - 2015-09-10 16:50 +0200
          Re: [PATCH] lib/vsprintf.c: increase the size of the field_width  variable Maurizio Lombardi <mlombard@redhat.com> - 2015-09-10 10:40 +0200

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