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Date:   Fri, 9 Jun 2023 21:35:49 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Peter Xu <peterx@redhat.com>
Cc:     Suren Baghdasaryan <surenb@google.com>, akpm@linux-foundation.org,
        hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com,
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        viro@zeniv.linux.org.uk, brauner@kernel.org,
        pasha.tatashin@soleen.com, linux-mm@kvack.org,
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Subject: Re: [PATCH v2 2/6] mm: handle swap page faults under VMA lock if
 page is uncontended
Message-ID: <ZIONJQGuhYiDnFdg@casper.infradead.org>
References: <20230609005158.2421285-1-surenb@google.com>
 <20230609005158.2421285-3-surenb@google.com>
 <ZIOKxoTlRzWQtQQR@x1n>
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On Fri, Jun 09, 2023 at 04:25:42PM -0400, Peter Xu wrote:
> >  bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
> >  			 unsigned int flags)
> >  {
> > +	/* Can't do this if not holding mmap_lock */
> > +	if (flags & FAULT_FLAG_VMA_LOCK)
> > +		return false;
> 
> If here what we need is the page lock, can we just conditionally release
> either mmap lock or vma lock depending on FAULT_FLAG_VMA_LOCK?

See patch 5 ...