From: Lorenzo Stoakes <lstoakes@gmail.com>
To: linux-mm@kvack.org
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
"Michal Hocko" <mhocko@kernel.org>, "Jan Kara" <jack@suse.cz>,
"Hugh Dickins" <hughd@google.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Rik van Riel" <riel@redhat.com>,
"Mel Gorman" <mgorman@techsingularity.net>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls
Date: Wed, 26 Oct 2016 00:46:31 +0100 [thread overview]
Message-ID: <20161025234631.GA5946@lucifer> (raw)
In-Reply-To: <20161025233609.5601-1-lstoakes@gmail.com>
The holdout for unexporting __get_user_pages_unlocked() is its invocation in
mm/process_vm_access.c: process_vm_rw_single_vec(), as this definitely _does_
seem to invoke VM_FAULT_RETRY behaviour which get_user_pages_remote() will not
trigger if we were to replace it with the latter.
I'm not sure how to proceed in this case - get_user_pages_remote() invocations
assume mmap_sem is held so can't offer VM_FAULT_RETRY behaviour as the lock
can't be assumed to be safe to release, and get_user_pages_unlocked() assumes
tsk, mm are set to current, current->mm respectively so we can't use that here
either.
Is it important to retain VM_FAULT_RETRY behaviour here, does it matter? If it
isn't so important then we can just go ahead and replace with
get_user_pages_remote() and unexport away.
Of course the whole idea of unexporting __get_user_pages_unlocked() might be
bogus so let me know in that case also :)
next prev parent reply other threads:[~2016-10-25 23:46 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-25 23:36 [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls Lorenzo Stoakes
2016-10-25 23:46 ` Lorenzo Stoakes [this message]
2016-10-26 9:15 ` Michal Hocko
2016-10-26 9:39 ` Lorenzo Stoakes
2016-10-26 9:54 ` Michal Hocko
2016-10-26 7:59 ` Lorenzo Stoakes
2016-10-26 9:07 ` Michal Hocko
2016-10-26 9:12 ` Michal Hocko
2016-10-26 9:25 ` [PATCH v2] " Lorenzo Stoakes
2016-10-27 0:12 ` Andrew Morton
2016-10-27 7:06 ` Lorenzo Stoakes
2016-10-27 9:27 ` Paolo Bonzini
2016-10-27 9:32 ` Lorenzo Stoakes
2016-10-27 9:35 ` Paolo Bonzini
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