Commit 1998cc04 authored by Shaohua Li's avatar Shaohua Li Committed by Linus Torvalds
Browse files

mm: make madvise(MADV_WILLNEED) support swap file prefetch 



Make madvise(MADV_WILLNEED) support swap file prefetch.  If memory is
swapout, this syscall can do swapin prefetch.  It has no impact if the
memory isn't swapout.

[akpm@linux-foundation.org: fix CONFIG_SWAP=n build]
[sasha.levin@oracle.com: fix BUG on madvise early failure]
Signed-off-by: default avatarShaohua Li <shli@fusionio.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a394cb8e

mm/madvise.c

+101 −4
Original line number Diff line number Diff line
@@ -16,6 +16,9 @@ 
#include <linux/ksm.h>

#include <linux/fs.h>

#include <linux/file.h>

#include <linux/blkdev.h>

#include <linux/swap.h>

#include <linux/swapops.h>



/*

 * Any behaviour which results in changes to the vma->vm_flags needs to
@@ -131,6 +134,84 @@ out: 
	return error;

}



#ifdef CONFIG_SWAP

static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,

	unsigned long end, struct mm_walk *walk)

{

	pte_t *orig_pte;

	struct vm_area_struct *vma = walk->private;

	unsigned long index;



	if (pmd_none_or_trans_huge_or_clear_bad(pmd))

		return 0;



	for (index = start; index != end; index += PAGE_SIZE) {

		pte_t pte;

		swp_entry_t entry;

		struct page *page;

		spinlock_t *ptl;



		orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);

		pte = *(orig_pte + ((index - start) / PAGE_SIZE));

		pte_unmap_unlock(orig_pte, ptl);



		if (pte_present(pte) || pte_none(pte) || pte_file(pte))

			continue;

		entry = pte_to_swp_entry(pte);

		if (unlikely(non_swap_entry(entry)))

			continue;



		page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,

								vma, index);

		if (page)

			page_cache_release(page);

	}



	return 0;

}



static void force_swapin_readahead(struct vm_area_struct *vma,

		unsigned long start, unsigned long end)

{

	struct mm_walk walk = {

		.mm = vma->vm_mm,

		.pmd_entry = swapin_walk_pmd_entry,

		.private = vma,

	};



	walk_page_range(start, end, &walk);



	lru_add_drain();	/* Push any new pages onto the LRU now */

}



static void force_shm_swapin_readahead(struct vm_area_struct *vma,

		unsigned long start, unsigned long end,

		struct address_space *mapping)

{

	pgoff_t index;

	struct page *page;

	swp_entry_t swap;



	for (; start < end; start += PAGE_SIZE) {

		index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;



		page = find_get_page(mapping, index);

		if (!radix_tree_exceptional_entry(page)) {

			if (page)

				page_cache_release(page);

			continue;

		}

		swap = radix_to_swp_entry(page);

		page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,

								NULL, 0);

		if (page)

			page_cache_release(page);

	}



	lru_add_drain();	/* Push any new pages onto the LRU now */

}

#endif		/* CONFIG_SWAP */



/*

 * Schedule all required I/O operations.  Do not wait for completion.

 */
@@ -140,6 +221,18 @@ static long madvise_willneed(struct vm_area_struct * vma, 
{

	struct file *file = vma->vm_file;



#ifdef CONFIG_SWAP

	if (!file || mapping_cap_swap_backed(file->f_mapping)) {

		*prev = vma;

		if (!file)

			force_swapin_readahead(vma, start, end);

		else

			force_shm_swapin_readahead(vma, start, end,

						file->f_mapping);

		return 0;

	}

#endif



	if (!file)

		return -EBADF;
@@ -371,6 +464,7 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) 
	int error = -EINVAL;

	int write;

	size_t len;

	struct blk_plug plug;



#ifdef CONFIG_MEMORY_FAILURE

	if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
@@ -410,18 +504,19 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) 
	if (vma && start > vma->vm_start)

		prev = vma;



	blk_start_plug(&plug);

	for (;;) {

		/* Still start < end. */

		error = -ENOMEM;

		if (!vma)

			goto out;

			goto out_plug;



		/* Here start < (end|vma->vm_end). */

		if (start < vma->vm_start) {

			unmapped_error = -ENOMEM;

			start = vma->vm_start;

			if (start >= end)

				goto out;

				goto out_plug;

		}



		/* Here vma->vm_start <= start < (end|vma->vm_end) */
@@ -432,18 +527,20 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) 
		/* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */

		error = madvise_vma(vma, &prev, start, tmp, behavior);

		if (error)

			goto out;

			goto out_plug;

		start = tmp;

		if (prev && start < prev->vm_end)

			start = prev->vm_end;

		error = unmapped_error;

		if (start >= end)

			goto out;

			goto out_plug;

		if (prev)

			vma = prev->vm_next;

		else	/* madvise_remove dropped mmap_sem */

			vma = find_vma(current->mm, start);

	}

out_plug:

	blk_finish_plug(&plug);

out:

	if (write)

		up_write(&current->mm->mmap_sem);

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