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Commit 1592eef0 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
Browse files

mm: add debugfs tunable for fault_around_order 



Let's allow people to tweak faultaround at runtime.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ning Qu <quning@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 99e3e53f

mm/memory.c

+61 −7
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ 
#include <linux/migrate.h>

#include <linux/string.h>

#include <linux/dma-debug.h>

#include <linux/debugfs.h>



#include <asm/io.h>

#include <asm/pgalloc.h>
@@ -3382,8 +3383,63 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address, 
}



#define FAULT_AROUND_ORDER 4

#define FAULT_AROUND_PAGES (1UL << FAULT_AROUND_ORDER)

#define FAULT_AROUND_MASK ~((1UL << (PAGE_SHIFT + FAULT_AROUND_ORDER)) - 1)



#ifdef CONFIG_DEBUG_FS

static unsigned int fault_around_order = FAULT_AROUND_ORDER;



static int fault_around_order_get(void *data, u64 *val)

{

	*val = fault_around_order;

	return 0;

}



static int fault_around_order_set(void *data, u64 val)

{

	BUILD_BUG_ON((1UL << FAULT_AROUND_ORDER) > PTRS_PER_PTE);

	if (1UL << val > PTRS_PER_PTE)

		return -EINVAL;

	fault_around_order = val;

	return 0;

}

DEFINE_SIMPLE_ATTRIBUTE(fault_around_order_fops,

		fault_around_order_get, fault_around_order_set, "%llu\n");



static int __init fault_around_debugfs(void)

{

	void *ret;



	ret = debugfs_create_file("fault_around_order",	0644, NULL, NULL,

			&fault_around_order_fops);

	if (!ret)

		pr_warn("Failed to create fault_around_order in debugfs");

	return 0;

}

late_initcall(fault_around_debugfs);



static inline unsigned long fault_around_pages(void)

{

	return 1UL << fault_around_order;

}



static inline unsigned long fault_around_mask(void)

{

	return ~((1UL << (PAGE_SHIFT + fault_around_order)) - 1);

}

#else

static inline unsigned long fault_around_pages(void)

{

	unsigned long nr_pages;



	nr_pages = 1UL << FAULT_AROUND_ORDER;

	BUILD_BUG_ON(nr_pages > PTRS_PER_PTE);

	return nr_pages;

}



static inline unsigned long fault_around_mask(void)

{

	return ~((1UL << (PAGE_SHIFT + FAULT_AROUND_ORDER)) - 1);

}

#endif



static void do_fault_around(struct vm_area_struct *vma, unsigned long address,

		pte_t *pte, pgoff_t pgoff, unsigned int flags)
@@ -3393,21 +3449,19 @@ static void do_fault_around(struct vm_area_struct *vma, unsigned long address, 
	struct vm_fault vmf;

	int off;



	BUILD_BUG_ON(FAULT_AROUND_PAGES > PTRS_PER_PTE);



	start_addr = max(address & FAULT_AROUND_MASK, vma->vm_start);

	start_addr = max(address & fault_around_mask(), vma->vm_start);

	off = ((address - start_addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);

	pte -= off;

	pgoff -= off;



	/*

	 *  max_pgoff is either end of page table or end of vma

	 *  or FAULT_AROUND_PAGES from pgoff, depending what is neast.

	 *  or fault_around_pages() from pgoff, depending what is neast.

	 */

	max_pgoff = pgoff - ((start_addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) +

		PTRS_PER_PTE - 1;

	max_pgoff = min3(max_pgoff, vma_pages(vma) + vma->vm_pgoff - 1,

			pgoff + FAULT_AROUND_PAGES - 1);

			pgoff + fault_around_pages() - 1);



	/* Check if it makes any sense to call ->map_pages */

	while (!pte_none(*pte)) {