From: Michal Hocko <mhocko@suse.com>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Andrew Morton <akpm@linux-foundation.org>,
Arnd Bergmann <arnd@arndb.de>, Oscar Salvador <osalvador@suse.de>,
Matthew Wilcox <willy@infradead.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Minchan Kim <minchan@kernel.org>, Jann Horn <jannh@google.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
Dave Hansen <dave.hansen@intel.com>,
Hugh Dickins <hughd@google.com>, Rik van Riel <riel@surriel.com>,
"Michael S . Tsirkin" <mst@redhat.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
Helge Deller <deller@gmx.de>, Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>,
linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org,
linux-parisc@vger.kernel.org, linux-xtensa@linux-xtensa.org,
linux-arch@vger.kernel.org
Subject: Re: [PATCH RFC] mm/madvise: introduce MADV_POPULATE to prefault/prealloc memory
Date: Fri, 19 Feb 2021 11:35:21 +0100 [thread overview]
Message-ID: <YC+UaTVUn0o4Zynz@dhcp22.suse.cz> (raw)
In-Reply-To: <20210217154844.12392-1-david@redhat.com>
On Wed 17-02-21 16:48:44, David Hildenbrand wrote:
[...]
I only got to the implementation now.
> +static long madvise_populate(struct vm_area_struct *vma,
> + struct vm_area_struct **prev,
> + unsigned long start, unsigned long end)
> +{
> + struct mm_struct *mm = vma->vm_mm;
> + unsigned long tmp_end;
> + int locked = 1;
> + long pages;
> +
> + *prev = vma;
> +
> + while (start < end) {
> + /*
> + * We might have temporarily dropped the lock. For example,
> + * our VMA might have been split.
> + */
> + if (!vma || start >= vma->vm_end) {
> + vma = find_vma(mm, start);
> + if (!vma)
> + return -ENOMEM;
> + }
Why do you need to find a vma when you already have one. do_madvise will
give you your vma already. I do understand that you want to finish the
vma for some errors but that shouldn't require handling vmas. You should
be in the shope of one here unless I miss anything.
> +
> + /* Bail out on incompatible VMA types. */
> + if (vma->vm_flags & (VM_IO | VM_PFNMAP) ||
> + !vma_is_accessible(vma)) {
> + return -EINVAL;
> + }
> +
> + /*
> + * Populate pages and take care of VM_LOCKED: simulate user
> + * space access.
> + *
> + * For private, writable mappings, trigger a write fault to
> + * break COW (i.e., shared zeropage). For other mappings (i.e.,
> + * read-only, shared), trigger a read fault.
> + */
> + tmp_end = min_t(unsigned long, end, vma->vm_end);
> + pages = populate_vma_page_range(vma, start, tmp_end, &locked);
> + if (!locked) {
> + mmap_read_lock(mm);
> + *prev = NULL;
> + vma = NULL;
> + }
> + if (pages < 0) {
> + switch (pages) {
> + case -EINTR:
> + case -ENOMEM:
> + return pages;
> + case -EHWPOISON:
> + /* Skip over any poisoned pages. */
> + start += PAGE_SIZE;
> + continue;
> + case -EBUSY:
> + case -EAGAIN:
> + continue;
> + default:
> + pr_warn_once("%s: unhandled return value: %ld\n",
> + __func__, pages);
> + return -ENOMEM;
> + }
> + }
> + start += pages * PAGE_SIZE;
> + }
> + return 0;
> +}
> +
> /*
> * Application wants to free up the pages and associated backing store.
> * This is effectively punching a hole into the middle of a file.
> @@ -934,6 +1001,8 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
> case MADV_FREE:
> case MADV_DONTNEED:
> return madvise_dontneed_free(vma, prev, start, end, behavior);
> + case MADV_POPULATE:
> + return madvise_populate(vma, prev, start, end);
> default:
> return madvise_behavior(vma, prev, start, end, behavior);
> }
> @@ -954,6 +1023,7 @@ madvise_behavior_valid(int behavior)
> case MADV_FREE:
> case MADV_COLD:
> case MADV_PAGEOUT:
> + case MADV_POPULATE:
> #ifdef CONFIG_KSM
> case MADV_MERGEABLE:
> case MADV_UNMERGEABLE:
> --
> 2.29.2
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-02-19 10:35 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 15:48 [PATCH RFC] mm/madvise: introduce MADV_POPULATE to prefault/prealloc memory David Hildenbrand
2021-02-17 16:46 ` Dave Hansen
2021-02-17 17:06 ` David Hildenbrand
2021-02-17 17:21 ` Vlastimil Babka
2021-02-18 11:07 ` Rolf Eike Beer
2021-02-18 11:27 ` David Hildenbrand
2021-02-18 10:25 ` Michal Hocko
2021-02-18 10:44 ` David Hildenbrand
2021-02-18 10:54 ` David Hildenbrand
2021-02-18 11:28 ` Michal Hocko
2021-02-18 11:27 ` Michal Hocko
2021-02-18 11:38 ` David Hildenbrand
2021-02-18 12:22 ` [PATCH RFC] madvise.2: Document MADV_POPULATE David Hildenbrand
2021-02-18 22:59 ` [PATCH RFC] mm/madvise: introduce MADV_POPULATE to prefault/prealloc memory Peter Xu
2021-02-19 8:20 ` David Hildenbrand
2021-02-19 16:31 ` Peter Xu
2021-02-19 17:13 ` David Hildenbrand
2021-02-19 19:14 ` David Hildenbrand
2021-02-19 19:25 ` Mike Kravetz
2021-02-20 9:01 ` David Hildenbrand
2021-02-19 19:23 ` Peter Xu
2021-02-19 20:04 ` David Hildenbrand
2021-02-22 12:46 ` Michal Hocko
2021-02-22 12:52 ` David Hildenbrand
2021-02-19 10:35 ` Michal Hocko [this message]
2021-02-19 10:43 ` David Hildenbrand
2021-02-19 11:04 ` Michal Hocko
2021-02-19 11:10 ` David Hildenbrand
2021-02-20 9:12 ` David Hildenbrand
2021-02-22 12:56 ` Michal Hocko
2021-02-22 12:59 ` David Hildenbrand
2021-02-22 13:19 ` Michal Hocko
2021-02-22 13:22 ` David Hildenbrand
2021-02-22 14:02 ` Michal Hocko
2021-02-22 15:30 ` David Hildenbrand
2021-02-24 14:25 ` David Hildenbrand
2021-02-24 14:38 ` David Hildenbrand
2021-02-25 8:41 ` David Hildenbrand
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