From: Jan Kara <jack@suse.cz>
To: John Hubbard <jhubbard@nvidia.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Alex Williamson" <alex.williamson@redhat.com>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Björn Töpel" <bjorn.topel@intel.com>,
"Christoph Hellwig" <hch@infradead.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
"Dave Chinner" <david@fromorbit.com>,
"David Airlie" <airlied@linux.ie>,
"David S . Miller" <davem@davemloft.net>,
"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
"Jason Gunthorpe" <jgg@ziepe.ca>, "Jens Axboe" <axboe@kernel.dk>,
"Jonathan Corbet" <corbet@lwn.net>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Magnus Karlsson" <magnus.karlsson@intel.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Michal Hocko" <mhocko@suse.com>,
"Mike Kravetz" <mike.kravetz@oracle.com>,
"Paul Mackerras" <paulus@samba.org>,
"Shuah Khan" <shuah@kernel.org>,
"Vlastimil Babka" <vbabka@suse.cz>,
bpf@vger.kernel.org, dri-devel@lists.freedesktop.org,
kvm@vger.kernel.org, linux-block@vger.kernel.org,
linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org,
linux-rdma@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
netdev@vger.kernel.org, linux-mm@kvack.org,
LKML <linux-kernel@vger.kernel.org>,
"Christoph Hellwig" <hch@lst.de>,
"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Subject: Re: [PATCH v6 02/24] mm/gup: factor out duplicate code from four routines
Date: Tue, 19 Nov 2019 11:19:10 +0100 [thread overview]
Message-ID: <20191119101910.GC25605@quack2.suse.cz> (raw)
In-Reply-To: <20191119081643.1866232-3-jhubbard@nvidia.com>
On Tue 19-11-19 00:16:21, John Hubbard wrote:
> 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@redhat.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Looks good to me now! You can add:
Reviewed-by: Jan Kara <jack@suse.cz>
Honza
> ---
> 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
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2019-11-19 10:19 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-19 8:16 [PATCH v6 00/24] mm/gup: track dma-pinned pages: FOLL_PIN John Hubbard
2019-11-19 8:16 ` [PATCH v6 01/24] mm/gup: pass flags arg to __gup_device_* functions John Hubbard
2019-11-19 8:16 ` [PATCH v6 02/24] mm/gup: factor out duplicate code from four routines John Hubbard
2019-11-19 10:19 ` Jan Kara [this message]
2019-11-19 8:16 ` [PATCH v6 03/24] mm/gup: move try_get_compound_head() to top, fix minor issues John Hubbard
2019-11-19 8:16 ` [PATCH v6 04/24] mm: Cleanup __put_devmap_managed_page() vs ->page_free() John Hubbard
2019-11-19 8:16 ` [PATCH v6 05/24] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages John Hubbard
2019-11-19 8:16 ` [PATCH v6 06/24] goldish_pipe: rename local pin_user_pages() routine John Hubbard
2019-11-19 8:16 ` [PATCH v6 07/24] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
2019-11-19 8:16 ` [PATCH v6 08/24] media/v4l2-core: set pages dirty upon releasing DMA buffers John Hubbard
2019-11-19 8:16 ` [PATCH v6 09/24] vfio, mm: fix get_user_pages_remote() and FOLL_LONGTERM John Hubbard
2019-11-19 8:16 ` [PATCH v6 10/24] mm/gup: introduce pin_user_pages*() and FOLL_PIN John Hubbard
2019-11-19 8:16 ` [PATCH v6 11/24] goldish_pipe: convert to pin_user_pages() and put_user_page() John Hubbard
2019-11-19 8:16 ` [PATCH v6 12/24] IB/{core,hw,umem}: set FOLL_PIN via pin_user_pages*(), fix up ODP John Hubbard
2019-11-19 8:16 ` [PATCH v6 13/24] mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote() John Hubbard
2019-11-19 8:16 ` [PATCH v6 14/24] drm/via: set FOLL_PIN via pin_user_pages_fast() John Hubbard
2019-11-19 8:16 ` [PATCH v6 15/24] fs/io_uring: set FOLL_PIN via pin_user_pages() John Hubbard
2019-11-19 16:10 ` Jens Axboe
2019-11-20 7:03 ` John Hubbard
2019-11-19 8:16 ` [PATCH v6 16/24] net/xdp: " John Hubbard
2019-11-19 8:16 ` [PATCH v6 17/24] mm/gup: track FOLL_PIN pages John Hubbard
2019-11-19 11:37 ` Jan Kara
2019-11-20 7:17 ` John Hubbard
2019-11-19 8:16 ` [PATCH v6 18/24] media/v4l2-core: pin_user_pages (FOLL_PIN) and put_user_page() conversion John Hubbard
2019-11-19 8:16 ` [PATCH v6 19/24] vfio, mm: " John Hubbard
2019-11-19 8:16 ` [PATCH v6 20/24] powerpc: book3s64: convert to pin_user_pages() and put_user_page() John Hubbard
2019-11-19 8:16 ` [PATCH v6 21/24] mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1" John Hubbard
2019-11-19 8:16 ` [PATCH v6 22/24] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2019-11-19 8:16 ` [PATCH v6 23/24] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard
2019-11-19 8:16 ` [PATCH v6 24/24] mm, tree-wide: rename put_user_page*() to unpin_user_page*() John Hubbard
2019-11-19 11:39 ` Jan Kara
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