From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [RFC PATCH for 4.21 04/16] mm: Introduce vm_map_user_ram,
 vm_unmap_user_ram
Date: Wed, 17 Oct 2018 09:27:22 +0900
Message-ID: <20181017002722.GA1068@jagdpanzerIV>
References: <20181010191936.7495-1-mathieu.desnoyers@efficios.com>
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To: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>, Peter Zijlstra <peterz@infradead.org>, "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>, Boqun Feng <boqun.feng@gmail.com>, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>, Andy Lutomirski <luto@amacapital.net>, Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>, Andrew Morton <akpm@linux-foundation.org>, Russell King <linux@arm.linux.org.uk>, Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>, Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>, Ben Maurer <bmaurer@fb.com>, Josh Triplett <josh@joshtriplett.org>, Linus Torvalds <torvalds@linux-foundation.org>, Catalin Marinas <catalin.marinas@arm.com>Will Deacon <w>
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On (10/16/18 14:30), Steven Rostedt wrote:
> > +void vm_unmap_user_ram(const void *mem, unsigned int count)
> > +{
> > +	unsigned long size = (unsigned long)count << PAGE_SHIFT;
> > +	unsigned long addr = (unsigned long)mem;
> > +	struct vmap_area *va;
> > +
> > +	might_sleep();
> > +	BUG_ON(!addr);
> > +	BUG_ON(addr < VMALLOC_START);
> > +	BUG_ON(addr > VMALLOC_END);
> > +	BUG_ON(!PAGE_ALIGNED(addr));
> > +
> > +	debug_check_no_locks_freed(mem, size);
> > +	va = find_vmap_area(addr);
> > +	BUG_ON(!va);
> > +	free_unmap_vmap_area(va);
> > +}
> > +EXPORT_SYMBOL(vm_unmap_user_ram);
> > +
> 
> Noticing this from Sergey's question in another patch, why are you
> using BUG_ON()? That's rather extreme and something we are trying to
> avoid adding more of (I still need to remove the BUG_ON()s I've added
> over ten years ago). I don't see why all these BUG_ON's can't be turned
> into:

+1

> 	if (WARN_ON(x))
> 		return;

Given that this somewhat MM-related, I'd may be say VM_WARN_ON().

	-ss