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 12:04:09 +0100 [thread overview]
Message-ID: <YC+bKSQdepXhqo0T@dhcp22.suse.cz> (raw)
In-Reply-To: <6e5a5bde-cedb-9d0a-f8c1-22406085b6b9@redhat.com>
On Fri 19-02-21 11:43:48, David Hildenbrand wrote:
> On 19.02.21 11:35, Michal Hocko wrote:
> > 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.
>
> See below, we might temporary drop the lock while not having processed all
> pages
>
> >
> > > +
> > > + /* 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;
>
> ^ here
>
> so, the VMA might have been replaced/split/... in the meantime.
>
> So to make forward progress, I have to lookup again. (similar. but different
> to madvise_dontneed_free()).
Right. Missed that.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-02-19 11:04 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
2021-02-19 10:43 ` David Hildenbrand
2021-02-19 11:04 ` Michal Hocko [this message]
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
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=YC+bKSQdepXhqo0T@dhcp22.suse.cz \
--to=mhocko@suse.com \
--cc=James.Bottomley@hansenpartnership.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=chris@zankel.net \
--cc=dave.hansen@intel.com \
--cc=david@redhat.com \
--cc=deller@gmx.de \
--cc=hughd@google.com \
--cc=ink@jurassic.park.msu.ru \
--cc=jannh@google.com \
--cc=jcmvbkbc@gmail.com \
--cc=jgg@ziepe.ca \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-alpha@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-parisc@vger.kernel.org \
--cc=linux-xtensa@linux-xtensa.org \
--cc=mattst88@gmail.com \
--cc=minchan@kernel.org \
--cc=mst@redhat.com \
--cc=osalvador@suse.de \
--cc=riel@surriel.com \
--cc=rth@twiddle.net \
--cc=tsbogend@alpha.franken.de \
--cc=vbabka@suse.cz \
--cc=willy@infradead.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).