linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Pingfan Liu <kernelfans@gmail.com>
To: linux-mm@kvack.org
Cc: Pingfan Liu <kernelfans@gmail.com>,
	Ira Weiny <ira.weiny@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Matthew Wilcox <willy@infradead.org>,
	John Hubbard <jhubbard@nvidia.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	Keith Busch <keith.busch@intel.com>,
	Christoph Hellwig <hch@infradead.org>,
	Shuah Khan <shuah@kernel.org>,
	linux-kernel@vger.kernel.org
Subject: [PATCHv5 2/3] mm/gup: fix omission of check on FOLL_LONGTERM in gup fast path
Date: Fri, 28 Feb 2020 19:32:29 +0800	[thread overview]
Message-ID: <1582889550-9101-3-git-send-email-kernelfans@gmail.com> (raw)
In-Reply-To: <1582889550-9101-1-git-send-email-kernelfans@gmail.com>

FOLL_LONGTERM suggests a pin which is going to be given to hardware and
can't move. It would truncate CMA permanently and should be excluded.

FOLL_LONGTERM has already been checked in the slow path, but not checked in
the fast path, which means a possible leak of CMA page to longterm pinned
requirement through this crack.

Place a check in try_get_compound_head() in the fast path.

Some note about the check:
Huge page's subpages have the same migrate type due to either
allocation from a free_list[] or alloc_contig_range() with param
MIGRATE_MOVABLE. So it is enough to check on a single subpage
by is_migrate_cma_page(subpage)

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
To: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/gup.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index cd8075e..f0d6804 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -33,9 +33,21 @@ struct follow_page_context {
  * Return the compound head page with ref appropriately incremented,
  * or NULL if that failed.
  */
-static inline struct page *try_get_compound_head(struct page *page, int refs)
+static inline struct page *try_get_compound_head(struct page *page, int refs,
+	unsigned int flags)
 {
-	struct page *head = compound_head(page);
+	struct page *head;
+
+	/*
+	 * Huge page's subpages have the same migrate type due to either
+	 * allocation from a free_list[] or alloc_contig_range() with param
+	 * MIGRATE_MOVABLE. So it is enough to check on a single subpage.
+	 */
+	if (unlikely(flags & FOLL_LONGTERM) &&
+		is_migrate_cma_page(page))
+		return NULL;
+
+	head = compound_head(page);
 
 	if (WARN_ON_ONCE(page_ref_count(head) < 0))
 		return NULL;
@@ -1908,7 +1920,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 		page = pte_page(pte);
 
-		head = try_get_compound_head(page, 1);
+		head = try_get_compound_head(page, 1, flags);
 		if (!head)
 			goto pte_unmap;
 
@@ -2083,7 +2095,7 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
 	page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(head, refs);
+	head = try_get_compound_head(head, refs, flags);
 	if (!head)
 		return 0;
 
@@ -2142,7 +2154,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
 	page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(pmd_page(orig), refs);
+	head = try_get_compound_head(pmd_page(orig), refs, flags);
 	if (!head)
 		return 0;
 
@@ -2174,7 +2186,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
 	page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(pud_page(orig), refs);
+	head = try_get_compound_head(pud_page(orig), refs, flags);
 	if (!head)
 		return 0;
 
@@ -2203,7 +2215,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
 	page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(pgd_page(orig), refs);
+	head = try_get_compound_head(pgd_page(orig), refs, flags);
 	if (!head)
 		return 0;
 
-- 
2.7.5



  parent reply	other threads:[~2020-02-28 11:35 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-28 11:32 [PATCHv5 0/3] fix omission of check on FOLL_LONGTERM in gup fast path Pingfan Liu
2020-02-28 11:32 ` [PATCHv5 1/3] mm/gup: rename nr as nr_pinned in internal_get_user_pages_fast() Pingfan Liu
2020-02-28 11:32 ` Pingfan Liu [this message]
2020-02-28 13:44   ` [PATCHv5 2/3] mm/gup: fix omission of check on FOLL_LONGTERM in gup fast path Jason Gunthorpe
2020-03-02  2:25     ` Pingfan Liu
2020-03-02 13:08       ` Jason Gunthorpe
2020-03-03 13:39         ` Pingfan Liu
2020-02-28 22:34   ` Ira Weiny
2020-03-02  2:28     ` Pingfan Liu
2020-03-02 23:51   ` John Hubbard
2020-03-03 13:38     ` Pingfan Liu
2020-02-28 11:32 ` [PATCHv5 3/3] mm/gup_benchemark: add LONGTERM_BENCHMARK test " Pingfan Liu
2020-02-28 15:43   ` Alexander Duyck
2020-03-02  2:38     ` Pingfan Liu
2020-03-02 23:42 ` [PATCHv5 0/3] fix omission of check on FOLL_LONGTERM " John Hubbard

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=1582889550-9101-3-git-send-email-kernelfans@gmail.com \
    --to=kernelfans@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=aneesh.kumar@linux.ibm.com \
    --cc=dan.j.williams@intel.com \
    --cc=hch@infradead.org \
    --cc=ira.weiny@intel.com \
    --cc=jhubbard@nvidia.com \
    --cc=keith.busch@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=rppt@linux.ibm.com \
    --cc=shuah@kernel.org \
    --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).