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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
	linux@arm.linux.org.uk, linux-arch@vger.kernel.org,
	linux-mm@kvack.org
Cc: will.deacon@arm.com, gary.robertson@linaro.org,
	christoffer.dall@linaro.org, peterz@infradead.org,
	anders.roxell@linaro.org, akpm@linux-foundation.org,
	dann.frazier@canonical.com, mark.rutland@arm.com,
	mgorman@suse.de, hughd@google.com,
	Steve Capper <steve.capper@linaro.org>
Subject: Re: [PATCH V4 1/6] mm: Introduce a general RCU get_user_pages_fast.
Date: Mon, 13 Oct 2014 11:52:26 +0530	[thread overview]
Message-ID: <87a9501obh.fsf@linux.vnet.ibm.com> (raw)
In-Reply-To: <1411740233-28038-2-git-send-email-steve.capper@linaro.org>

Steve Capper <steve.capper@linaro.org> writes:

.....

> +
> +static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
> +		unsigned long end, int write, struct page **pages, int *nr)
> +{
> +	struct page *head, *page, *tail;
> +	int refs;
> +
> +	if (write && !pmd_write(orig))
> +		return 0;
> +
> +	refs = 0;
> +	head = pmd_page(orig);
> +	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
> +	tail = page;
> +	do {
> +		VM_BUG_ON_PAGE(compound_head(page) != head, page);
> +		pages[*nr] = page;
> +		(*nr)++;
> +		page++;
> +		refs++;
> +	} while (addr += PAGE_SIZE, addr != end);
> +
> +	if (!page_cache_add_speculative(head, refs)) {
> +		*nr -= refs;
> +		return 0;
> +	}
> +
> +	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
> +		*nr -= refs;
> +		while (refs--)
> +			put_page(head);
> +		return 0;
> +	}
> +
> +	/*
> +	 * Any tail pages need their mapcount reference taken before we
> +	 * return. (This allows the THP code to bump their ref count when
> +	 * they are split into base pages).
> +	 */
> +	while (refs--) {
> +		if (PageTail(tail))
> +			get_huge_page_tail(tail);
> +		tail++;
> +	}
> +
> +	return 1;
> +}
> +
.....

> +static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
> +		int write, struct page **pages, int *nr)
> +{
> +	unsigned long next;
> +	pmd_t *pmdp;
> +
> +	pmdp = pmd_offset(&pud, addr);
> +	do {
> +		pmd_t pmd = ACCESS_ONCE(*pmdp);
> +
> +		next = pmd_addr_end(addr, end);
> +		if (pmd_none(pmd) || pmd_trans_splitting(pmd))
> +			return 0;
> +
> +		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {

We don't check the _PAGE_PRESENT here


> +			/*
> +			 * NUMA hinting faults need to be handled in the GUP
> +			 * slowpath for accounting purposes and so that they
> +			 * can be serialised against THP migration.
> +			 */
> +			if (pmd_numa(pmd))
> +				return 0;
> +
> +			if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
> +				pages, nr))
> +				return 0;
> +
> +		} else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
> +				return 0;
> +	} while (pmdp++, addr = next, addr != end);
> +
> +	return 1;
> +}
> +

-aneesh

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WARNING: multiple messages have this Message-ID (diff)
From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Steve Capper <steve.capper@linaro.org>,
	linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
	linux@arm.linux.org.uk, linux-arch@vger.kernel.org,
	linux-mm@kvack.org
Cc: will.deacon@arm.com, gary.robertson@linaro.org,
	christoffer.dall@linaro.org, peterz@infradead.org,
	anders.roxell@linaro.org, akpm@linux-foundation.org,
	dann.frazier@canonical.com, mark.rutland@arm.com,
	mgorman@suse.de, hughd@google.com
Subject: Re: [PATCH V4 1/6] mm: Introduce a general RCU get_user_pages_fast.
Date: Mon, 13 Oct 2014 11:52:26 +0530	[thread overview]
Message-ID: <87a9501obh.fsf@linux.vnet.ibm.com> (raw)
Message-ID: <20141013062226.-3pKfEiD_Bf447m2cOoK6FQbaZA4p2fpF6nx2-Fod88@z> (raw)
In-Reply-To: <1411740233-28038-2-git-send-email-steve.capper@linaro.org>

Steve Capper <steve.capper@linaro.org> writes:

.....

> +
> +static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
> +		unsigned long end, int write, struct page **pages, int *nr)
> +{
> +	struct page *head, *page, *tail;
> +	int refs;
> +
> +	if (write && !pmd_write(orig))
> +		return 0;
> +
> +	refs = 0;
> +	head = pmd_page(orig);
> +	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
> +	tail = page;
> +	do {
> +		VM_BUG_ON_PAGE(compound_head(page) != head, page);
> +		pages[*nr] = page;
> +		(*nr)++;
> +		page++;
> +		refs++;
> +	} while (addr += PAGE_SIZE, addr != end);
> +
> +	if (!page_cache_add_speculative(head, refs)) {
> +		*nr -= refs;
> +		return 0;
> +	}
> +
> +	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
> +		*nr -= refs;
> +		while (refs--)
> +			put_page(head);
> +		return 0;
> +	}
> +
> +	/*
> +	 * Any tail pages need their mapcount reference taken before we
> +	 * return. (This allows the THP code to bump their ref count when
> +	 * they are split into base pages).
> +	 */
> +	while (refs--) {
> +		if (PageTail(tail))
> +			get_huge_page_tail(tail);
> +		tail++;
> +	}
> +
> +	return 1;
> +}
> +
.....

> +static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
> +		int write, struct page **pages, int *nr)
> +{
> +	unsigned long next;
> +	pmd_t *pmdp;
> +
> +	pmdp = pmd_offset(&pud, addr);
> +	do {
> +		pmd_t pmd = ACCESS_ONCE(*pmdp);
> +
> +		next = pmd_addr_end(addr, end);
> +		if (pmd_none(pmd) || pmd_trans_splitting(pmd))
> +			return 0;
> +
> +		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {

We don't check the _PAGE_PRESENT here


> +			/*
> +			 * NUMA hinting faults need to be handled in the GUP
> +			 * slowpath for accounting purposes and so that they
> +			 * can be serialised against THP migration.
> +			 */
> +			if (pmd_numa(pmd))
> +				return 0;
> +
> +			if (!gup_huge_pmd(pmd, pmdp, addr, next, write,
> +				pages, nr))
> +				return 0;
> +
> +		} else if (!gup_pte_range(pmd, addr, next, write, pages, nr))
> +				return 0;
> +	} while (pmdp++, addr = next, addr != end);
> +
> +	return 1;
> +}
> +

-aneesh


  parent reply	other threads:[~2014-10-13  6:22 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-26 14:03 [PATCH V4 0/6] RCU get_user_pages_fast and __get_user_pages_fast Steve Capper
2014-09-26 14:03 ` Steve Capper
2014-09-26 14:03 ` [PATCH V4 1/6] mm: Introduce a general RCU get_user_pages_fast Steve Capper
2014-09-26 14:03   ` Steve Capper
2014-09-29 21:51   ` Hugh Dickins
2014-09-29 21:51     ` Hugh Dickins
2014-10-01 11:11     ` Catalin Marinas
2014-10-01 11:11       ` Catalin Marinas
2014-10-02 16:00     ` Steve Capper
2014-10-02 16:00       ` Steve Capper
2014-10-02 12:19   ` Andrea Arcangeli
2014-10-02 12:19     ` Andrea Arcangeli
2014-10-02 16:18     ` Steve Capper
2014-10-02 16:18       ` Steve Capper
2014-10-02 16:54       ` Andrea Arcangeli
2014-10-02 16:54         ` Andrea Arcangeli
2014-10-13  5:15     ` Aneesh Kumar K.V
2014-10-13  5:21       ` David Miller
2014-10-13  5:21         ` David Miller
2014-10-13 11:44         ` Steve Capper
2014-10-13 11:44           ` Steve Capper
2014-10-13 16:06           ` David Miller
2014-10-14 12:38             ` Steve Capper
2014-10-14 12:38               ` Steve Capper
2014-10-14 16:30               ` David Miller
2014-10-14 16:30                 ` David Miller
2014-10-13 17:04           ` Aneesh Kumar K.V
2014-10-13  6:22   ` Aneesh Kumar K.V [this message]
2014-10-13  6:22     ` Aneesh Kumar K.V
2014-09-26 14:03 ` [PATCH V4 2/6] arm: mm: Introduce special ptes for LPAE Steve Capper
2014-09-26 14:03   ` Steve Capper
2014-09-26 14:03 ` [PATCH V4 3/6] arm: mm: Enable HAVE_RCU_TABLE_FREE logic Steve Capper
2014-09-26 14:03   ` Steve Capper
2014-09-26 14:03 ` [PATCH V4 4/6] arm: mm: Enable RCU fast_gup Steve Capper
2014-09-26 14:03   ` Steve Capper
2014-09-26 14:03 ` [PATCH V4 5/6] arm64: mm: Enable HAVE_RCU_TABLE_FREE logic Steve Capper
2014-09-26 14:03 ` [PATCH V4 6/6] arm64: mm: Enable RCU fast_gup Steve Capper
2015-02-27 12:42 ` [PATCH V4 0/6] RCU get_user_pages_fast and __get_user_pages_fast Jon Masters
2015-02-27 12:42   ` Jon Masters
2015-02-27 13:20   ` Mark Rutland
2015-03-02 14:16     ` Mark Rutland
2015-03-02  2:10   ` PMD update corruption (sync question) Jon Masters
2015-03-02  2:10     ` Jon Masters
2015-03-02  5:58     ` Jon Masters
2015-03-02  5:58       ` Jon Masters
2015-03-02 10:50       ` Catalin Marinas
2015-03-02 11:06         ` Jon Masters
2015-03-02 11:06           ` Jon Masters
2015-03-02 12:31           ` Peter Zijlstra
2015-03-02 12:31             ` Peter Zijlstra
2015-03-02 12:40             ` Geert Uytterhoeven
2015-03-02 12:40               ` Geert Uytterhoeven
2015-03-02 22:21         ` Jon Masters
2015-03-02 22:21           ` Jon Masters
2015-03-02 22:29           ` Jon Masters
2015-03-02 22:29             ` Jon Masters
2015-03-03  9:06           ` Arnd Bergmann
2015-03-03 15:46             ` Jon Masters
2015-03-03 15:46               ` Jon Masters

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