Re: [PATCH v4 1/9] hugetlb: Pass vma into huge_pte_alloc()

From: Peter Xu <peterx@redhat.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Axel Rasmussen" <axelrasmussen@google.com>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Alexey Dobriyan" <adobriyan@gmail.com>,
	"Andrea Arcangeli" <aarcange@redhat.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Anshuman Khandual" <anshuman.khandual@arm.com>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Chinwen Chang" <chinwen.chang@mediatek.com>,
	"Huang Ying" <ying.huang@intel.com>,
	"Ingo Molnar" <mingo@redhat.com>, "Jann Horn" <jannh@google.com>,
	"Jerome Glisse" <jglisse@redhat.com>,
	"Lokesh Gidra" <lokeshgidra@google.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	"Michael Ellerman" <mpe@ellerman.id.au>,
	"Michal Koutný" <mkoutny@suse.com>,
	"Michel Lespinasse" <walken@google.com>,
	"Mike Rapoport" <rppt@linux.vnet.ibm.com>,
	"Nicholas Piggin" <npiggin@gmail.com>, "Shaohua Li" <shli@fb.com>,
	"Shawn Anastasio" <shawn@anastas.io>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Steven Price" <steven.price@arm.com>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org, "Adam Ruprecht" <ruprecht@google.com>,
	"Cannon Matthews" <cannonmatthews@google.com>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	"David Rientjes" <rientjes@google.com>,
	"Oliver Upton" <oupton@google.com>
Subject: Re: [PATCH v4 1/9] hugetlb: Pass vma into huge_pte_alloc()
Date: Mon, 1 Feb 2021 17:16:54 -0500	[thread overview]
Message-ID: <20210201221654.GJ260413@xz-x1> (raw)
In-Reply-To: <f1afa616-c4f5-daaa-6865-8bbc3c93b71a@oracle.com>

On Mon, Feb 01, 2021 at 01:53:14PM -0800, Mike Kravetz wrote:
> On 2/1/21 1:38 PM, Mike Kravetz wrote:
> > On 1/28/21 3:42 PM, Axel Rasmussen wrote:
> >> From: Peter Xu <peterx@redhat.com>
> >>
> >> It is a preparation work to be able to behave differently in the per
> >> architecture huge_pte_alloc() according to different VMA attributes.
> >>
> >> Signed-off-by: Peter Xu <peterx@redhat.com>
> >> [axelrasmussen@google.com: fixed typo in arch/mips/mm/hugetlbpage.c]
> >> Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
> >> ---
> >>  arch/arm64/mm/hugetlbpage.c   | 2 +-
> >>  arch/ia64/mm/hugetlbpage.c    | 3 ++-
> >>  arch/mips/mm/hugetlbpage.c    | 4 ++--
> >>  arch/parisc/mm/hugetlbpage.c  | 2 +-
> >>  arch/powerpc/mm/hugetlbpage.c | 3 ++-
> >>  arch/s390/mm/hugetlbpage.c    | 2 +-
> >>  arch/sh/mm/hugetlbpage.c      | 2 +-
> >>  arch/sparc/mm/hugetlbpage.c   | 2 +-
> >>  include/linux/hugetlb.h       | 2 +-
> >>  mm/hugetlb.c                  | 6 +++---
> >>  mm/userfaultfd.c              | 2 +-
> >>  11 files changed, 16 insertions(+), 14 deletions(-)
> > 
> > Sorry for the delay in reviewing.
> > 
> > huge_pmd_share() will do a find_vma() to get the vma.  So, it would be
> > 'possible' to not add an extra argument to huge_pmd_alloc() and simply
> > do the uffd_disable_huge_pmd_share() check inside vma_shareable.  This
> > would reduce the amount of modified code, but would not be as efficient.
> > I prefer passing the vma argument as is done here.
> > 
> > Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> 
> 
> Another thought.
> 
> We should pass the vma to huge_pmd_share to avoid the find_vma.

Agreed.  Seems not relevant to this series, but should be a very nice add-on
after this patch can land.  Thanks,

-- 
Peter Xu