From: Vlastimil Babka <vbabka@suse.cz>
To: David Hildenbrand <david@redhat.com>, linux-kernel@vger.kernel.org
Cc: x86@kernel.org, linux-alpha@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
sparclinux@vger.kernel.org, linux-um@lists.infradead.org,
etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org,
linux-media@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-perf-users@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kselftest@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Jason Gunthorpe <jgg@ziepe.ca>,
John Hubbard <jhubbard@nvidia.com>, Peter Xu <peterx@redhat.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Hugh Dickins <hughd@google.com>, Nadav Amit <namit@vmware.com>,
Matthew Wilcox <willy@infradead.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Muchun Song <songmuchun@bytedance.com>,
Shuah Khan <shuah@kernel.org>,
Lucas Stach <l.stach@pengutronix.de>,
David Airlie <airlied@gmail.com>,
Oded Gabbay <ogabbay@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Christoph Hellwig <hch@infradead.org>,
Alex Williamson <alex.williamson@redhat.com>
Subject: Re: [PATCH mm-unstable v1 08/20] mm: extend FAULT_FLAG_UNSHARE support to anything in a COW mapping
Date: Tue, 22 Nov 2022 16:35:52 +0100 [thread overview]
Message-ID: <34835490-57d7-4e26-7474-008b2c4c6b39@suse.cz> (raw)
In-Reply-To: <20221116102659.70287-9-david@redhat.com>
On 11/16/22 11:26, David Hildenbrand wrote:
> Extend FAULT_FLAG_UNSHARE to break COW on anything mapped into a
> COW (i.e., private writable) mapping and adjust the documentation
> accordingly.
>
> FAULT_FLAG_UNSHARE will now also break COW when encountering the shared
> zeropage, a pagecache page, a PFNMAP, ... inside a COW mapping, by
> properly replacing the mapped page/pfn by a private copy (an exclusive
> anonymous page).
>
> Note that only do_wp_page() needs care: hugetlb_wp() already handles
> FAULT_FLAG_UNSHARE correctly. wp_huge_pmd()/wp_huge_pud() also handles it
> correctly, for example, splitting the huge zeropage on FAULT_FLAG_UNSHARE
> such that we can handle FAULT_FLAG_UNSHARE on the PTE level.
>
> This change is a requirement for reliable long-term R/O pinning in
> COW mappings.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> include/linux/mm_types.h | 8 ++++----
> mm/memory.c | 4 ----
> 2 files changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 5e7f4fac1e78..5e9aaad8c7b2 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -1037,9 +1037,9 @@ typedef struct {
> * @FAULT_FLAG_REMOTE: The fault is not for current task/mm.
> * @FAULT_FLAG_INSTRUCTION: The fault was during an instruction fetch.
> * @FAULT_FLAG_INTERRUPTIBLE: The fault can be interrupted by non-fatal signals.
> - * @FAULT_FLAG_UNSHARE: The fault is an unsharing request to unshare (and mark
> - * exclusive) a possibly shared anonymous page that is
> - * mapped R/O.
> + * @FAULT_FLAG_UNSHARE: The fault is an unsharing request to break COW in a
> + * COW mapping, making sure that an exclusive anon page is
> + * mapped after the fault.
> * @FAULT_FLAG_ORIG_PTE_VALID: whether the fault has vmf->orig_pte cached.
> * We should only access orig_pte if this flag set.
> *
> @@ -1064,7 +1064,7 @@ typedef struct {
> *
> * The combination FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE is illegal.
> * FAULT_FLAG_UNSHARE is ignored and treated like an ordinary read fault when
> - * no existing R/O-mapped anonymous page is encountered.
> + * applied to mappings that are not COW mappings.
> */
> enum fault_flag {
> FAULT_FLAG_WRITE = 1 << 0,
> diff --git a/mm/memory.c b/mm/memory.c
> index d47ad33c6487..56b21ab1e4d2 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3432,10 +3432,6 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf)
> }
> wp_page_reuse(vmf);
> return 0;
> - } else if (unshare) {
> - /* No anonymous page -> nothing to do. */
> - pte_unmap_unlock(vmf->pte, vmf->ptl);
> - return 0;
> }
> copy:
> /*
next prev parent reply other threads:[~2022-11-22 15:36 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-16 10:26 [PATCH mm-unstable v1 00/20] mm/gup: remove FOLL_FORCE usage from drivers (reliable R/O long-term pinning) David Hildenbrand
2022-11-16 10:26 ` [PATCH mm-unstable v1 01/20] selftests/vm: anon_cow: prepare for non-anonymous COW tests David Hildenbrand
2022-11-18 16:20 ` Vlastimil Babka
2022-11-16 10:26 ` [PATCH mm-unstable v1 02/20] selftests/vm: cow: basic COW tests for non-anonymous pages David Hildenbrand
2022-11-16 10:26 ` [PATCH mm-unstable v1 03/20] selftests/vm: cow: R/O long-term pinning reliability tests for non-anon pages David Hildenbrand
2022-11-16 10:26 ` [PATCH mm-unstable v1 04/20] mm: add early FAULT_FLAG_UNSHARE consistency checks David Hildenbrand
2022-11-18 16:45 ` Vlastimil Babka
2022-11-16 10:26 ` [PATCH mm-unstable v1 05/20] mm: add early FAULT_FLAG_WRITE " David Hildenbrand
2022-11-18 17:03 ` Vlastimil Babka
2022-11-16 10:26 ` [PATCH mm-unstable v1 06/20] mm: rework handling in do_wp_page() based on private vs. shared mappings David Hildenbrand
2022-11-22 14:20 ` Vlastimil Babka
2022-11-16 10:26 ` [PATCH mm-unstable v1 07/20] mm: don't call vm_ops->huge_fault() in wp_huge_pmd()/wp_huge_pud() for private mappings David Hildenbrand
2022-11-22 14:50 ` Vlastimil Babka
2022-11-16 10:26 ` [PATCH mm-unstable v1 08/20] mm: extend FAULT_FLAG_UNSHARE support to anything in a COW mapping David Hildenbrand
2022-11-22 15:35 ` Vlastimil Babka [this message]
2022-11-16 10:26 ` [PATCH mm-unstable v1 09/20] mm/gup: reliable R/O long-term pinning in COW mappings David Hildenbrand
2022-11-16 10:42 ` Daniel Vetter
2022-11-22 16:29 ` Vlastimil Babka
2022-11-24 1:29 ` John Hubbard
2022-11-16 10:26 ` [PATCH mm-unstable v1 10/20] RDMA/umem: remove FOLL_FORCE usage David Hildenbrand
2022-11-17 0:45 ` Jason Gunthorpe
2022-11-16 10:26 ` [PATCH mm-unstable v1 11/20] RDMA/usnic: " David Hildenbrand
2022-11-17 0:45 ` Jason Gunthorpe
2022-11-16 10:26 ` [PATCH mm-unstable v1 12/20] RDMA/siw: " David Hildenbrand
2022-11-17 0:46 ` Jason Gunthorpe
2022-11-16 10:26 ` [PATCH mm-unstable v1 13/20] media: videobuf-dma-sg: " David Hildenbrand
2022-11-16 10:48 ` Daniel Vetter
2022-11-23 13:17 ` Hans Verkuil
2022-11-16 10:26 ` [PATCH mm-unstable v1 14/20] drm/etnaviv: " David Hildenbrand
2022-11-16 10:49 ` Daniel Vetter
2022-11-16 10:26 ` [PATCH mm-unstable v1 15/20] media: pci/ivtv: " David Hildenbrand
2022-11-23 13:18 ` Hans Verkuil
2022-11-16 10:26 ` [PATCH mm-unstable v1 16/20] mm/frame-vector: " David Hildenbrand
2022-11-16 10:50 ` Daniel Vetter
2022-11-23 13:26 ` Hans Verkuil
2022-11-23 14:28 ` Hans Verkuil
2022-11-27 10:35 ` David Hildenbrand
2022-11-28 8:17 ` Hans Verkuil
2022-11-28 8:18 ` David Hildenbrand
2022-11-28 8:26 ` Hans Verkuil
2022-11-28 8:57 ` Tomasz Figa
2022-11-28 22:59 ` Andrew Morton
2022-11-29 8:48 ` David Hildenbrand
2022-11-29 9:08 ` Hans Verkuil
2022-11-29 9:15 ` David Hildenbrand
2022-11-16 10:26 ` [PATCH mm-unstable v1 17/20] drm/exynos: " David Hildenbrand
2022-11-16 10:50 ` Daniel Vetter
2022-11-16 10:26 ` [PATCH mm-unstable v1 18/20] RDMA/hw/qib/qib_user_pages: " David Hildenbrand
2022-11-16 10:26 ` [PATCH mm-unstable v1 19/20] habanalabs: " David Hildenbrand
2022-11-16 10:26 ` [PATCH mm-unstable v1 20/20] mm: rename FOLL_FORCE to FOLL_PTRACE David Hildenbrand
2022-11-16 18:16 ` Linus Torvalds
2022-11-16 18:53 ` David Hildenbrand
2022-11-17 22:58 ` Kees Cook
2022-11-17 23:20 ` Linus Torvalds
2022-11-18 0:31 ` Kees Cook
2022-11-18 11:09 ` Peter Zijlstra
2022-11-18 22:29 ` Kees Cook
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=34835490-57d7-4e26-7474-008b2c4c6b39@suse.cz \
--to=vbabka@suse.cz \
--cc=aarcange@redhat.com \
--cc=airlied@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=alex.williamson@redhat.com \
--cc=arnd@arndb.de \
--cc=david@redhat.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=etnaviv@lists.freedesktop.org \
--cc=gregkh@linuxfoundation.org \
--cc=hch@infradead.org \
--cc=hughd@google.com \
--cc=jgg@ziepe.ca \
--cc=jhubbard@nvidia.com \
--cc=l.stach@pengutronix.de \
--cc=linux-alpha@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=linux-samsung-soc@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=linux-um@lists.infradead.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mike.kravetz@oracle.com \
--cc=namit@vmware.com \
--cc=ogabbay@kernel.org \
--cc=peterx@redhat.com \
--cc=shuah@kernel.org \
--cc=songmuchun@bytedance.com \
--cc=sparclinux@vger.kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=willy@infradead.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).