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Message-ID: <20191119081643.1866232-3-jhubbard@nvidia.com>
Date: Tue, 19 Nov 2019 00:16:21 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: Al Viro <viro@...iv.linux.org.uk>,
Alex Williamson <alex.williamson@...hat.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Björn Töpel <bjorn.topel@...el.com>,
Christoph Hellwig <hch@...radead.org>,
Dan Williams <dan.j.williams@...el.com>,
Daniel Vetter <daniel@...ll.ch>,
Dave Chinner <david@...morbit.com>,
David Airlie <airlied@...ux.ie>,
"David S . Miller" <davem@...emloft.net>,
Ira Weiny <ira.weiny@...el.com>, Jan Kara <jack@...e.cz>,
Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>,
Jonathan Corbet <corbet@....net>,
Jérôme Glisse <jglisse@...hat.com>,
Magnus Karlsson <magnus.karlsson@...el.com>,
"Mauro Carvalho Chehab" <mchehab@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>,
Michal Hocko <mhocko@...e.com>,
Mike Kravetz <mike.kravetz@...cle.com>,
"Paul Mackerras" <paulus@...ba.org>, Shuah Khan <shuah@...nel.org>,
Vlastimil Babka <vbabka@...e.cz>, <bpf@...r.kernel.org>,
<dri-devel@...ts.freedesktop.org>, <kvm@...r.kernel.org>,
<linux-block@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<linux-fsdevel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
<linux-media@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
<linuxppc-dev@...ts.ozlabs.org>, <netdev@...r.kernel.org>,
<linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
John Hubbard <jhubbard@...dia.com>,
"Christoph Hellwig" <hch@....de>,
"Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>
Subject: [PATCH v6 02/24] mm/gup: factor out duplicate code from four routines
There are four locations in gup.c that have a fair amount of code
duplication. This means that changing one requires making the same
changes in four places, not to mention reading the same code four
times, and wondering if there are subtle differences.
Factor out the common code into static functions, thus reducing the
overall line count and the code's complexity.
Also, take the opportunity to slightly improve the efficiency of the
error cases, by doing a mass subtraction of the refcount, surrounded
by get_page()/put_page().
Also, further simplify (slightly), by waiting until the the successful
end of each routine, to increment *nr.
Reviewed-by: Jérôme Glisse <jglisse@...hat.com>
Cc: Jan Kara <jack@...e.cz>
Cc: Ira Weiny <ira.weiny@...el.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
Signed-off-by: John Hubbard <jhubbard@...dia.com>
---
mm/gup.c | 91 ++++++++++++++++++++++----------------------------------
1 file changed, 36 insertions(+), 55 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index 85caf76b3012..f3c7d6625817 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1969,6 +1969,25 @@ static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
}
#endif
+static int __record_subpages(struct page *page, unsigned long addr,
+ unsigned long end, struct page **pages)
+{
+ int nr;
+
+ for (nr = 0; addr != end; addr += PAGE_SIZE)
+ pages[nr++] = page++;
+
+ return nr;
+}
+
+static void put_compound_head(struct page *page, int refs)
+{
+ /* Do a get_page() first, in case refs == page->_refcount */
+ get_page(page);
+ page_ref_sub(page, refs);
+ put_page(page);
+}
+
#ifdef CONFIG_ARCH_HAS_HUGEPD
static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
unsigned long sz)
@@ -1998,32 +2017,20 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
/* hugepages are never "special" */
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
- refs = 0;
head = pte_page(pte);
-
page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
- do {
- VM_BUG_ON(compound_head(page) != head);
- pages[*nr] = page;
- (*nr)++;
- page++;
- refs++;
- } while (addr += PAGE_SIZE, addr != end);
+ refs = __record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(head, refs);
- if (!head) {
- *nr -= refs;
+ if (!head)
return 0;
- }
if (unlikely(pte_val(pte) != pte_val(*ptep))) {
- /* Could be optimized better */
- *nr -= refs;
- while (refs--)
- put_page(head);
+ put_compound_head(head, refs);
return 0;
}
+ *nr += refs;
SetPageReferenced(head);
return 1;
}
@@ -2071,28 +2078,19 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
pages, nr);
}
- refs = 0;
page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
- do {
- pages[*nr] = page;
- (*nr)++;
- page++;
- refs++;
- } while (addr += PAGE_SIZE, addr != end);
+ refs = __record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(pmd_page(orig), refs);
- if (!head) {
- *nr -= refs;
+ if (!head)
return 0;
- }
if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
- *nr -= refs;
- while (refs--)
- put_page(head);
+ put_compound_head(head, refs);
return 0;
}
+ *nr += refs;
SetPageReferenced(head);
return 1;
}
@@ -2114,28 +2112,19 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
pages, nr);
}
- refs = 0;
page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
- do {
- pages[*nr] = page;
- (*nr)++;
- page++;
- refs++;
- } while (addr += PAGE_SIZE, addr != end);
+ refs = __record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(pud_page(orig), refs);
- if (!head) {
- *nr -= refs;
+ if (!head)
return 0;
- }
if (unlikely(pud_val(orig) != pud_val(*pudp))) {
- *nr -= refs;
- while (refs--)
- put_page(head);
+ put_compound_head(head, refs);
return 0;
}
+ *nr += refs;
SetPageReferenced(head);
return 1;
}
@@ -2151,28 +2140,20 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
return 0;
BUILD_BUG_ON(pgd_devmap(orig));
- refs = 0;
+
page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
- do {
- pages[*nr] = page;
- (*nr)++;
- page++;
- refs++;
- } while (addr += PAGE_SIZE, addr != end);
+ refs = __record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(pgd_page(orig), refs);
- if (!head) {
- *nr -= refs;
+ if (!head)
return 0;
- }
if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
- *nr -= refs;
- while (refs--)
- put_page(head);
+ put_compound_head(head, refs);
return 0;
}
+ *nr += refs;
SetPageReferenced(head);
return 1;
}
--
2.24.0
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