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Message-ID: <20180112184821.GB7590@bombadil.infradead.org>
Date: Fri, 12 Jan 2018 10:48:21 -0800
From: Matthew Wilcox <willy@...radead.org>
To: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
Cc: paulmck@...ux.vnet.ibm.com, peterz@...radead.org,
akpm@...ux-foundation.org, kirill@...temov.name,
ak@...ux.intel.com, mhocko@...nel.org, dave@...olabs.net,
jack@...e.cz, benh@...nel.crashing.org, mpe@...erman.id.au,
paulus@...ba.org, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, hpa@...or.com,
Will Deacon <will.deacon@....com>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Alexei Starovoitov <alexei.starovoitov@...il.com>,
kemi.wang@...el.com, sergey.senozhatsky.work@...il.com,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
haren@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
npiggin@...il.com, bsingharora@...il.com,
Tim Chen <tim.c.chen@...ux.intel.com>,
linuxppc-dev@...ts.ozlabs.org, x86@...nel.org
Subject: Re: [PATCH v6 16/24] mm: Protect mm_rb tree with a rwlock
On Fri, Jan 12, 2018 at 06:26:00PM +0100, Laurent Dufour wrote:
> -static void __vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
> +static void __vma_rb_erase(struct vm_area_struct *vma, struct mm_struct *mm)
> {
> + struct rb_root *root = &mm->mm_rb;
> /*
> * Note rb_erase_augmented is a fairly large inline function,
> * so make sure we instantiate it only once with our desired
> * augmented rbtree callbacks.
> */
> +#ifdef CONFIG_SPF
> + write_lock(&mm->mm_rb_lock);
> +#endif
> rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
> +#ifdef CONFIG_SPF
> + write_unlock(&mm->mm_rb_lock); /* wmb */
> +#endif
I can't say I love this. Have you considered:
#ifdef CONFIG_SPF
#define vma_rb_write_lock(mm) write_lock(&mm->mm_rb_lock)
#define vma_rb_write_unlock(mm) write_unlock(&mm->mm_rb_lock)
#else
#define vma_rb_write_lock(mm) do { } while (0)
#define vma_rb_write_unlock(mm) do { } while (0)
#endif
Also, SPF is kind of uninformative. CONFIG_MM_SPF might be better?
Or perhaps even CONFIG_SPECULATIVE_PAGE_FAULT, just to make it really
painful to do these one-liner ifdefs that make the code so hard to read.
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