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Date:   Wed, 17 Oct 2018 11:00:01 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc:     rostedt <rostedt@goodmis.org>,
        Peter Zijlstra <peterz@infradead.org>,
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        Boqun Feng <boqun.feng@gmail.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-api <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 <will.deacon@arm.com>,
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        Joel Fernandes <joelaf@google.com>
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In-Reply-To: <20181017002722.GA1068@jagdpanzerIV>
References: <20181010191936.7495-1-mathieu.desnoyers@efficios.com> <20181010191936.7495-5-mathieu.desnoyers@efficios.com> <20181016143016.10da89bd@gandalf.local.home> <20181017002722.GA1068@jagdpanzerIV>
Subject: Re: [RFC PATCH for 4.21 04/16] mm: Introduce vm_map_user_ram,
 vm_unmap_user_ram
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Thread-Topic: Introduce vm_map_user_ram, vm_unmap_user_ram
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----- On Oct 16, 2018, at 8:27 PM, Sergey Senozhatsky sergey.senozhatsky.work@gmail.com wrote:

> 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().

Good point, will do!

So I'll do one cleanup patch for vm_unmap_ram(), and I'll modify the new vm_unmap_user_ram().

Thanks,

Mathieu

> 
> 	-ss

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com