From: David Hildenbrand <david@redhat.com>
To: Peter Xu <peterx@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Hugh Dickins <hughd@google.com>, Maya Gokhale <gokhale2@llnl.gov>,
Jerome Glisse <jglisse@redhat.com>,
Pavel Emelyanov <xemul@virtuozzo.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Martin Cracauer <cracauer@cons.org>,
Marty McFadden <mcfadden8@llnl.gov>, Shaohua Li <shli@fb.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Denis Plotnikov <dplotnikov@virtuozzo.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>
Subject: Re: [PATCH v3 3/7] mm: Introduce FAULT_FLAG_INTERRUPTIBLE
Date: Wed, 11 Sep 2019 12:15:51 +0200 [thread overview]
Message-ID: <865710d6-8fff-25ea-ef91-7cf31166ac79@redhat.com> (raw)
In-Reply-To: <20190911071007.20077-4-peterx@redhat.com>
On 11.09.19 09:10, Peter Xu wrote:
> handle_userfaultfd() is currently the only one place in the kernel
> page fault procedures that can respond to non-fatal userspace signals.
> It was trying to detect such an allowance by checking against USER &
> KILLABLE flags, which was "un-official".
>
> In this patch, we introduced a new flag (FAULT_FLAG_INTERRUPTIBLE) to
> show that the fault handler allows the fault procedure to respond even
> to non-fatal signals. Meanwhile, add this new flag to the default
> fault flags so that all the page fault handlers can benefit from the
> new flag. With that, replacing the userfault check to this one.
>
> Since the line is getting even longer, clean up the fault flags a bit
> too to ease TTY users.
>
> Although we've got a new flag and applied it, we shouldn't have any
> functional change with this patch so far.
>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> fs/userfaultfd.c | 4 +---
> include/linux/mm.h | 39 ++++++++++++++++++++++++++++-----------
> 2 files changed, 29 insertions(+), 14 deletions(-)
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index ccbdbd62f0d8..4a8ad2dc2b6f 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -462,9 +462,7 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
> uwq.ctx = ctx;
> uwq.waken = false;
>
> - return_to_userland =
> - (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) ==
> - (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE);
> + return_to_userland = vmf->flags & FAULT_FLAG_INTERRUPTIBLE;
> blocking_state = return_to_userland ? TASK_INTERRUPTIBLE :
> TASK_KILLABLE;
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 57fb5c535f8e..53ec7abb8472 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -383,22 +383,38 @@ extern unsigned int kobjsize(const void *objp);
> */
> extern pgprot_t protection_map[16];
>
> -#define FAULT_FLAG_WRITE 0x01 /* Fault was a write access */
> -#define FAULT_FLAG_MKWRITE 0x02 /* Fault was mkwrite of existing pte */
> -#define FAULT_FLAG_ALLOW_RETRY 0x04 /* Retry fault if blocking */
> -#define FAULT_FLAG_RETRY_NOWAIT 0x08 /* Don't drop mmap_sem and wait when retrying */
> -#define FAULT_FLAG_KILLABLE 0x10 /* The fault task is in SIGKILL killable region */
> -#define FAULT_FLAG_TRIED 0x20 /* Second try */
> -#define FAULT_FLAG_USER 0x40 /* The fault originated in userspace */
> -#define FAULT_FLAG_REMOTE 0x80 /* faulting for non current tsk/mm */
> -#define FAULT_FLAG_INSTRUCTION 0x100 /* The fault was during an instruction fetch */
> +/**
> + * Fault flag definitions.
> + *
> + * @FAULT_FLAG_WRITE: Fault was a write fault.
> + * @FAULT_FLAG_MKWRITE: Fault was mkwrite of existing PTE.
> + * @FAULT_FLAG_ALLOW_RETRY: Allow to retry the fault if blocked.
> + * @FAULT_FLAG_RETRY_NOWAIT: Don't drop mmap_sem and wait when retrying.
> + * @FAULT_FLAG_KILLABLE: The fault task is in SIGKILL killable region.
> + * @FAULT_FLAG_TRIED: The fault has been tried once.
> + * @FAULT_FLAG_USER: The fault originated in userspace.
> + * @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.
> + */
> +#define FAULT_FLAG_WRITE 0x01
> +#define FAULT_FLAG_MKWRITE 0x02
> +#define FAULT_FLAG_ALLOW_RETRY 0x04
> +#define FAULT_FLAG_RETRY_NOWAIT 0x08
> +#define FAULT_FLAG_KILLABLE 0x10
> +#define FAULT_FLAG_TRIED 0x20
> +#define FAULT_FLAG_USER 0x40
> +#define FAULT_FLAG_REMOTE 0x80
> +#define FAULT_FLAG_INSTRUCTION 0x100
> +#define FAULT_FLAG_INTERRUPTIBLE 0x200
>
> /*
> * The default fault flags that should be used by most of the
> * arch-specific page fault handlers.
> */
> #define FAULT_FLAG_DEFAULT (FAULT_FLAG_ALLOW_RETRY | \
> - FAULT_FLAG_KILLABLE)
> + FAULT_FLAG_KILLABLE | \
> + FAULT_FLAG_INTERRUPTIBLE)
>
> #define FAULT_FLAG_TRACE \
> { FAULT_FLAG_WRITE, "WRITE" }, \
> @@ -409,7 +425,8 @@ extern pgprot_t protection_map[16];
> { FAULT_FLAG_TRIED, "TRIED" }, \
> { FAULT_FLAG_USER, "USER" }, \
> { FAULT_FLAG_REMOTE, "REMOTE" }, \
> - { FAULT_FLAG_INSTRUCTION, "INSTRUCTION" }
> + { FAULT_FLAG_INSTRUCTION, "INSTRUCTION" }, \
> + { FAULT_FLAG_INTERRUPTIBLE, "INTERRUPTIBLE" }
>
> /*
> * vm_fault is filled by the the pagefault handler and passed to the vma's
>
Reviewed-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2019-09-11 10:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 7:10 [PATCH v3 0/7] mm: Page fault enhancements Peter Xu
2019-09-11 7:10 ` [PATCH v3 1/7] mm/gup: Rename "nonblocking" to "locked" where proper Peter Xu
2019-09-11 7:10 ` [PATCH v3 2/7] mm: Introduce FAULT_FLAG_DEFAULT Peter Xu
2019-09-11 7:10 ` [PATCH v3 3/7] mm: Introduce FAULT_FLAG_INTERRUPTIBLE Peter Xu
2019-09-11 10:15 ` David Hildenbrand [this message]
2019-09-11 7:10 ` [PATCH v3 4/7] mm: Return faster for non-fatal signals in user mode faults Peter Xu
2019-09-11 7:10 ` [PATCH v3 5/7] userfaultfd: Don't retake mmap_sem to emulate NOPAGE Peter Xu
2019-09-11 7:10 ` [PATCH v3 6/7] mm: Allow VM_FAULT_RETRY for multiple times Peter Xu
2019-09-11 7:10 ` [PATCH v3 7/7] mm/gup: " Peter Xu
2019-09-11 9:45 ` [PATCH v3.1 " Peter Xu
2019-09-11 9:47 ` [PATCH v3 " Linus Torvalds
2019-09-12 3:05 ` Peter Xu
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