From: "Liam R. Howlett" <Liam.Howlett@oracle.com>
To: Suren Baghdasaryan <surenb@google.com>
Cc: Matthew Wilcox <willy@infradead.org>,
linux-mm@kvack.org, netdev@vger.kernel.org,
Arjun Roy <arjunroy@google.com>
Subject: Re: [RFC] Make find_tcp_vma() more efficient
Date: Tue, 14 May 2024 18:12:26 -0400 [thread overview]
Message-ID: <l3abhimtyv24oogb5l2is7hml6fcs6vlthbd7n4rmnyou24e5l@capndvics4kt> (raw)
In-Reply-To: <CAJuCfpHxpZVnpM2bE25MeFK7CrSsO_pGaYuwVNzre47bb1Jh_w@mail.gmail.com>
* Suren Baghdasaryan <surenb@google.com> [240503 18:29]:
> On Fri, Apr 26, 2024 at 10:15 AM Matthew Wilcox <willy@infradead.org> wrote:
> >
> > Liam asked me if we could do away with the "bool *mmap_locked"
> > parameter, and the problem is that some architctures don't support
> > CONFIG_PER_VMA_LOCK yet. But we can abstract it ... something like this
> > maybe?
> >
> > (not particularly proposing this for inclusion; just wrote it and want
> > to get it out of my tree so I can get back to other projects. If anyone
> > wants it, they can test it and submit it for inclusion and stick my
> > S-o-B on it)
>
> I went through all uses of vma_end_read() to convince myself this is
> safe with CONFIG_PER_VMA_LOCK=n and the change seems fine from
> correctness POV. However the fact that in this configuration
> lock_vma_under_mmap_lock()==NOP and vma_end_read()==mmap_read_unlock()
> does not feel right to me. Current code is more explicit about which
> lock is held and I think it's easier to understand.
> A new interface like below might be a bit better but I'm not sure if
> it's worth it:
>
...
We could do something like we do in the release_fault_lock(), but
without using the FAULT flag..
/* Naming is hard. */
static inline void release_vma_modification_lock(
struct vm_area_struct *vma)
{
#ifdef CONFIG_PER_VMA_LOCK
if (rwsem_is_locked(&vma->vm_lock->lock))
vma_end_read(vma);
else
mmap_read_unlock(vma->vm_mm);
#else
mmap_read_unlock(vma->vm_mm);
#endif
}
prev parent reply other threads:[~2024-05-14 22:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 17:15 [RFC] Make find_tcp_vma() more efficient Matthew Wilcox
2024-05-03 22:29 ` Suren Baghdasaryan
2024-05-14 22:12 ` Liam R. Howlett [this message]
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