From: Peter Xu <peterx@redhat.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Kirill Shutemov <kirill@shutemov.name>,
Wei Zhang <wzam@amazon.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Matthew Wilcox <willy@infradead.org>,
Miaohe Lin <linmiaohe@huawei.com>,
Andrea Arcangeli <aarcange@redhat.com>,
peterx@redhat.com, Gal Pressman <galpress@amazon.com>,
Jan Kara <jack@suse.cz>, Jann Horn <jannh@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Kirill Tkhai <ktkhai@virtuozzo.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
David Gibson <david@gibson.dropbear.id.au>,
Christoph Hellwig <hch@lst.de>
Subject: [PATCH v2 4/4] hugetlb: Do early cow when page pinned on src mm
Date: Thu, 4 Feb 2021 09:50:33 -0500 [thread overview]
Message-ID: <20210204145033.136755-5-peterx@redhat.com> (raw)
In-Reply-To: <20210204145033.136755-1-peterx@redhat.com>
This is the last missing piece of the COW-during-fork effort when there're
pinned pages found. One can reference 70e806e4e645 ("mm: Do early cow for
pinned pages during fork() for ptes", 2020-09-27) for more information, since
we do similar things here rather than pte this time, but just for hugetlb.
Signed-off-by: Peter Xu <peterx@redhat.com>
---
mm/hugetlb.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 56 insertions(+), 5 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9e6ea96bf33b..5793936e00ef 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3734,11 +3734,27 @@ static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
return false;
}
+static void
+hugetlb_copy_page(struct vm_area_struct *vma, pte_t *ptep, unsigned long addr,
+ struct page *old_page, struct page *new_page)
+{
+ struct hstate *h = hstate_vma(vma);
+ unsigned int psize = pages_per_huge_page(h);
+
+ copy_user_huge_page(new_page, old_page, addr, vma, psize);
+ __SetPageUptodate(new_page);
+ ClearPagePrivate(new_page);
+ set_page_huge_active(new_page);
+ set_huge_pte_at(vma->vm_mm, addr, ptep, make_huge_pte(vma, new_page, 1));
+ hugepage_add_new_anon_rmap(new_page, vma, addr);
+ hugetlb_count_add(psize, vma->vm_mm);
+}
+
int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
struct vm_area_struct *vma)
{
pte_t *src_pte, *dst_pte, entry, dst_entry;
- struct page *ptepage;
+ struct page *ptepage, *prealloc = NULL;
unsigned long addr;
int cow;
struct hstate *h = hstate_vma(vma);
@@ -3787,7 +3803,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
dst_entry = huge_ptep_get(dst_pte);
if ((dst_pte == src_pte) || !huge_pte_none(dst_entry))
continue;
-
+again:
dst_ptl = huge_pte_lock(h, dst, dst_pte);
src_ptl = huge_pte_lockptr(h, src, src_pte);
spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
@@ -3816,6 +3832,39 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
}
set_huge_swap_pte_at(dst, addr, dst_pte, entry, sz);
} else {
+ entry = huge_ptep_get(src_pte);
+ ptepage = pte_page(entry);
+ get_page(ptepage);
+
+ /*
+ * This is a rare case where we see pinned hugetlb
+ * pages while they're prone to COW. We need to do the
+ * COW earlier during fork.
+ *
+ * When pre-allocating the page we need to be without
+ * all the locks since we could sleep when allocate.
+ */
+ if (unlikely(page_needs_cow_for_dma(vma, ptepage))) {
+ if (!prealloc) {
+ put_page(ptepage);
+ spin_unlock(src_ptl);
+ spin_unlock(dst_ptl);
+ prealloc = alloc_huge_page(vma, addr, 1);
+ if (!prealloc) {
+ ret = -ENOMEM;
+ break;
+ }
+ goto again;
+ }
+ hugetlb_copy_page(vma, dst_pte, addr, ptepage,
+ prealloc);
+ put_page(ptepage);
+ spin_unlock(src_ptl);
+ spin_unlock(dst_ptl);
+ prealloc = NULL;
+ continue;
+ }
+
if (cow) {
/*
* No need to notify as we are downgrading page
@@ -3826,9 +3875,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
*/
huge_ptep_set_wrprotect(src, addr, src_pte);
}
- entry = huge_ptep_get(src_pte);
- ptepage = pte_page(entry);
- get_page(ptepage);
+
page_dup_rmap(ptepage, true);
set_huge_pte_at(dst, addr, dst_pte, entry);
hugetlb_count_add(pages_per_huge_page(h), dst);
@@ -3842,6 +3889,10 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
else
i_mmap_unlock_read(mapping);
+ /* Free the preallocated page if not used at last */
+ if (prealloc)
+ put_page(prealloc);
+
return ret;
}
--
2.26.2
next prev parent reply other threads:[~2021-02-04 14:55 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-04 14:50 [PATCH v2 0/4] mm/hugetlb: Early cow on fork, and a few cleanups Peter Xu
2021-02-04 14:50 ` [PATCH v2 1/4] hugetlb: Dedup the code to add a new file_region Peter Xu
2021-02-04 14:50 ` [PATCH v2 2/4] hugetlg: Break earlier in add_reservation_in_range() when we can Peter Xu
2021-02-04 14:50 ` [PATCH v2 3/4] mm: Introduce page_needs_cow_for_dma() for deciding whether cow Peter Xu
2021-02-04 17:54 ` Linus Torvalds
2021-02-04 19:25 ` Peter Xu
2021-02-04 23:20 ` Jason Gunthorpe
2021-02-05 0:50 ` Peter Xu
2021-02-04 14:50 ` Peter Xu [this message]
2021-02-04 23:25 ` [PATCH v2 4/4] hugetlb: Do early cow when page pinned on src mm Mike Kravetz
2021-02-05 1:43 ` Peter Xu
2021-02-05 5:11 ` Mike Kravetz
2021-02-05 16:05 ` Peter Xu
[not found] ` <329ADC08-552E-423B-9230-99643B81C14A@amazon.com>
2021-02-05 15:51 ` Peter Xu
2021-02-07 9:09 ` Gal Pressman
2021-02-07 15:31 ` Peter Xu
2021-02-04 20:20 ` [PATCH v2 5/4] mm: Use is_cow_mapping() across tree where proper Peter Xu
2021-02-04 20:26 ` Linus Torvalds
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=20210204145033.136755-5-peterx@redhat.com \
--to=peterx@redhat.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=david@gibson.dropbear.id.au \
--cc=galpress@amazon.com \
--cc=hch@lst.de \
--cc=jack@suse.cz \
--cc=jannh@google.com \
--cc=jgg@ziepe.ca \
--cc=kirill@shutemov.name \
--cc=ktkhai@virtuozzo.com \
--cc=linmiaohe@huawei.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mike.kravetz@oracle.com \
--cc=rppt@linux.vnet.ibm.com \
--cc=torvalds@linux-foundation.org \
--cc=willy@infradead.org \
--cc=wzam@amazon.com \
/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).