[mirror_ubuntu-jammy-kernel.git] / mm / fremap.c

/*
 *   linux/mm/fremap.c
 * 
 * Explicit pagetable population and nonlinear (random) mappings support.
 *
 * started by Ingo Molnar, Copyright (C) 2002, 2003
 */
#include <linux/backing-dev.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/file.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/swapops.h>
#include <linux/rmap.h>
#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/mmu_notifier.h>

#include <asm/mmu_context.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

#include "internal.h"

static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
			unsigned long addr, pte_t *ptep)
{
	pte_t pte = *ptep;

	if (pte_present(pte)) {
		struct page *page;

		flush_cache_page(vma, addr, pte_pfn(pte));
		pte = ptep_clear_flush(vma, addr, ptep);
		page = vm_normal_page(vma, addr, pte);
		if (page) {
			if (pte_dirty(pte))
				set_page_dirty(page);
			page_remove_rmap(page);
			page_cache_release(page);
			update_hiwater_rss(mm);
			dec_mm_counter(mm, file_rss);
		}
	} else {
		if (!pte_file(pte))
			free_swap_and_cache(pte_to_swp_entry(pte));
		pte_clear_not_present_full(mm, addr, ptep, 0);
	}
}

/*
 * Install a file pte to a given virtual memory address, release any
 * previously existing mapping.
 */
static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
		unsigned long addr, unsigned long pgoff, pgprot_t prot)
{
	int err = -ENOMEM;
	pte_t *pte;
	spinlock_t *ptl;

	pte = get_locked_pte(mm, addr, &ptl);
	if (!pte)
		goto out;

	if (!pte_none(*pte))
		zap_pte(mm, vma, addr, pte);

	set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
	/*
	 * We don't need to run update_mmu_cache() here because the "file pte"
	 * being installed by install_file_pte() is not a real pte - it's a
	 * non-present entry (like a swap entry), noting what file offset should
	 * be mapped there when there's a fault (in a non-linear vma where
	 * that's not obvious).
	 */
	pte_unmap_unlock(pte, ptl);
	err = 0;
out:
	return err;
}

static int populate_range(struct mm_struct *mm, struct vm_area_struct *vma,
			unsigned long addr, unsigned long size, pgoff_t pgoff)
{
	int err;

	do {
		err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot);
		if (err)
			return err;

		size -= PAGE_SIZE;
		addr += PAGE_SIZE;
		pgoff++;
	} while (size);

        return 0;

}

/**
 * sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
 * @start: start of the remapped virtual memory range
 * @size: size of the remapped virtual memory range
 * @prot: new protection bits of the range (see NOTE)
 * @pgoff: to-be-mapped page of the backing store file
 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
 *
 * sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
 * (shared backing store file).
 *
 * This syscall works purely via pagetables, so it's the most efficient
 * way to map the same (large) file into a given virtual window. Unlike
 * mmap()/mremap() it does not create any new vmas. The new mappings are
 * also safe across swapout.
 *
 * NOTE: the @prot parameter right now is ignored (but must be zero),
 * and the vma's default protection is used. Arbitrary protections
 * might be implemented in the future.
 */
SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
		unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
{
	struct mm_struct *mm = current->mm;
	struct address_space *mapping;
	unsigned long end = start + size;
	struct vm_area_struct *vma;
	int err = -EINVAL;
	int has_write_lock = 0;

	if (prot)
		return err;
	/*
	 * Sanitize the syscall parameters:
	 */
	start = start & PAGE_MASK;
	size = size & PAGE_MASK;

	/* Does the address range wrap, or is the span zero-sized? */
	if (start + size <= start)
		return err;

	/* Can we represent this offset inside this architecture's pte's? */
#if PTE_FILE_MAX_BITS < BITS_PER_LONG
	if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
		return err;
#endif

	/* We need down_write() to change vma->vm_flags. */
	down_read(&mm->mmap_sem);
 retry:
	vma = find_vma(mm, start);

	/*
	 * Make sure the vma is shared, that it supports prefaulting,
	 * and that the remapped range is valid and fully within
	 * the single existing vma.  vm_private_data is used as a
	 * swapout cursor in a VM_NONLINEAR vma.
	 */
	if (!vma || !(vma->vm_flags & VM_SHARED))
		goto out;

	if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
		goto out;

	if (!(vma->vm_flags & VM_CAN_NONLINEAR))
		goto out;

	if (end <= start || start < vma->vm_start || end > vma->vm_end)
		goto out;

	/* Must set VM_NONLINEAR before any pages are populated. */
	if (!(vma->vm_flags & VM_NONLINEAR)) {
		/* Don't need a nonlinear mapping, exit success */
		if (pgoff == linear_page_index(vma, start)) {
			err = 0;
			goto out;
		}

		if (!has_write_lock) {
			up_read(&mm->mmap_sem);
			down_write(&mm->mmap_sem);
			has_write_lock = 1;
			goto retry;
		}
		mapping = vma->vm_file->f_mapping;
		/*
		 * page_mkclean doesn't work on nonlinear vmas, so if
		 * dirty pages need to be accounted, emulate with linear
		 * vmas.
		 */
		if (mapping_cap_account_dirty(mapping)) {
			unsigned long addr;
			struct file *file = vma->vm_file;

			flags &= MAP_NONBLOCK;
			get_file(file);
			addr = mmap_region(file, start, size,
					flags, vma->vm_flags, pgoff);
			fput(file);
			if (IS_ERR_VALUE(addr)) {
				err = addr;
			} else {
				BUG_ON(addr != start);
				err = 0;
			}
			goto out;
		}
		spin_lock(&mapping->i_mmap_lock);
		flush_dcache_mmap_lock(mapping);
		vma->vm_flags |= VM_NONLINEAR;
		vma_prio_tree_remove(vma, &mapping->i_mmap);
		vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
		flush_dcache_mmap_unlock(mapping);
		spin_unlock(&mapping->i_mmap_lock);
	}

	if (vma->vm_flags & VM_LOCKED) {
		/*
		 * drop PG_Mlocked flag for over-mapped range
		 */
		unsigned int saved_flags = vma->vm_flags;
		munlock_vma_pages_range(vma, start, start + size);
		vma->vm_flags = saved_flags;
	}

	mmu_notifier_invalidate_range_start(mm, start, start + size);
	err = populate_range(mm, vma, start, size, pgoff);
	mmu_notifier_invalidate_range_end(mm, start, start + size);
	if (!err && !(flags & MAP_NONBLOCK)) {
		if (vma->vm_flags & VM_LOCKED) {
			/*
			 * might be mapping previously unmapped range of file
			 */
			mlock_vma_pages_range(vma, start, start + size);
		} else {
			if (unlikely(has_write_lock)) {
				downgrade_write(&mm->mmap_sem);
				has_write_lock = 0;
			}
			make_pages_present(start, start+size);
		}
	}

	/*
	 * We can't clear VM_NONLINEAR because we'd have to do
	 * it after ->populate completes, and that would prevent
	 * downgrading the lock.  (Locks can't be upgraded).
	 */

out:
	if (likely(!has_write_lock))
		up_read(&mm->mmap_sem);
	else
		up_write(&mm->mmap_sem);

	return err;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/mm/fremap.c
	3	*
	4	* Explicit pagetable population and nonlinear (random) mappings support.
	5	*
	6	* started by Ingo Molnar, Copyright (C) 2002, 2003
	7	*/
4af3c9cc	8	#include <linux/backing-dev.h>
1da177e4 LT	9	#include <linux/mm.h>
	10	#include <linux/swap.h>
	11	#include <linux/file.h>
	12	#include <linux/mman.h>
	13	#include <linux/pagemap.h>
	14	#include <linux/swapops.h>
	15	#include <linux/rmap.h>
	16	#include <linux/module.h>
	17	#include <linux/syscalls.h>
cddb8a5c	18	#include <linux/mmu_notifier.h>
1da177e4 LT	19
	20	#include <asm/mmu_context.h>
	21	#include <asm/cacheflush.h>
	22	#include <asm/tlbflush.h>
	23
ba470de4 RR	24	#include "internal.h"
ba470de4 RR	25
d0217ac0	26	static void zap_pte(struct mm_struct mm, struct vm_area_struct vma,
1da177e4 LT	27	unsigned long addr, pte_t *ptep)
	28	{
	29	pte_t pte = *ptep;
	30
1da177e4	31	if (pte_present(pte)) {
d0217ac0 NP	32	struct page *page;
d0217ac0 NP	33
6aab341e	34	flush_cache_page(vma, addr, pte_pfn(pte));
1da177e4	35	pte = ptep_clear_flush(vma, addr, ptep);
6aab341e LT	36	page = vm_normal_page(vma, addr, pte);
	37	if (page) {
	38	if (pte_dirty(pte))
	39	set_page_dirty(page);
edc315fd	40	page_remove_rmap(page);
6aab341e	41	page_cache_release(page);
d0217ac0 NP	42	update_hiwater_rss(mm);
d0217ac0 NP	43	dec_mm_counter(mm, file_rss);
1da177e4 LT	44	}
	45	} else {
	46	if (!pte_file(pte))
	47	free_swap_and_cache(pte_to_swp_entry(pte));
9888a1ca	48	pte_clear_not_present_full(mm, addr, ptep, 0);
1da177e4 LT	49	}
	50	}
	51
1da177e4 LT	52	/*
	53	* Install a file pte to a given virtual memory address, release any
	54	* previously existing mapping.
	55	*/
d0217ac0	56	static int install_file_pte(struct mm_struct mm, struct vm_area_struct vma,
1da177e4 LT	57	unsigned long addr, unsigned long pgoff, pgprot_t prot)
	58	{
	59	int err = -ENOMEM;
	60	pte_t *pte;
c74df32c	61	spinlock_t *ptl;
1da177e4	62
c9cfcddf	63	pte = get_locked_pte(mm, addr, &ptl);
1da177e4	64	if (!pte)
c74df32c	65	goto out;
1da177e4	66
d0217ac0 NP	67	if (!pte_none(*pte))
d0217ac0 NP	68	zap_pte(mm, vma, addr, pte);
1da177e4 LT	69
1da177e4 LT	70	set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
668e0d8f HD	71	/*
	72	* We don't need to run update_mmu_cache() here because the "file pte"
	73	* being installed by install_file_pte() is not a real pte - it's a
	74	* non-present entry (like a swap entry), noting what file offset should
	75	* be mapped there when there's a fault (in a non-linear vma where
	76	* that's not obvious).
	77	*/
c74df32c HD	78	pte_unmap_unlock(pte, ptl);
	79	err = 0;
	80	out:
1da177e4 LT	81	return err;
	82	}
	83
54cb8821 NP	84	static int populate_range(struct mm_struct mm, struct vm_area_struct vma,
	85	unsigned long addr, unsigned long size, pgoff_t pgoff)
	86	{
	87	int err;
	88
	89	do {
	90	err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot);
	91	if (err)
	92	return err;
	93
	94	size -= PAGE_SIZE;
	95	addr += PAGE_SIZE;
	96	pgoff++;
	97	} while (size);
	98
	99	return 0;
	100
	101	}
	102
8d63494f RD	103	/**
8d63494f RD	104	* sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
1da177e4 LT	105	* @start: start of the remapped virtual memory range
1da177e4 LT	106	* @size: size of the remapped virtual memory range
8d63494f RD	107	* @prot: new protection bits of the range (see NOTE)
8d63494f RD	108	* @pgoff: to-be-mapped page of the backing store file
1da177e4 LT	109	* @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
1da177e4 LT	110	*
8d63494f RD	111	* sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
	112	* (shared backing store file).
	113	*
	114	* This syscall works purely via pagetables, so it's the most efficient
1da177e4 LT	115	* way to map the same (large) file into a given virtual window. Unlike
	116	* mmap()/mremap() it does not create any new vmas. The new mappings are
	117	* also safe across swapout.
	118	*
7682486b	119	* NOTE: the @prot parameter right now is ignored (but must be zero),
8d63494f RD	120	* and the vma's default protection is used. Arbitrary protections
8d63494f RD	121	* might be implemented in the future.
1da177e4	122	*/
6a6160a7 HC	123	SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
6a6160a7 HC	124	unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
1da177e4 LT	125	{
	126	struct mm_struct *mm = current->mm;
	127	struct address_space *mapping;
	128	unsigned long end = start + size;
	129	struct vm_area_struct *vma;
	130	int err = -EINVAL;
	131	int has_write_lock = 0;
	132
8d63494f	133	if (prot)
1da177e4 LT	134	return err;
	135	/*
	136	* Sanitize the syscall parameters:
	137	*/
	138	start = start & PAGE_MASK;
	139	size = size & PAGE_MASK;
	140
	141	/* Does the address range wrap, or is the span zero-sized? */
	142	if (start + size <= start)
	143	return err;
	144
	145	/* Can we represent this offset inside this architecture's pte's? */
	146	#if PTE_FILE_MAX_BITS < BITS_PER_LONG
	147	if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
	148	return err;
	149	#endif
	150
	151	/* We need down_write() to change vma->vm_flags. */
	152	down_read(&mm->mmap_sem);
	153	retry:
	154	vma = find_vma(mm, start);
	155
	156	/*
	157	* Make sure the vma is shared, that it supports prefaulting,
	158	* and that the remapped range is valid and fully within
	159	* the single existing vma. vm_private_data is used as a
101d2be7	160	* swapout cursor in a VM_NONLINEAR vma.
1da177e4	161	*/
54cb8821 NP	162	if (!vma \|\| !(vma->vm_flags & VM_SHARED))
	163	goto out;
	164
	165	if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
	166	goto out;
	167
dd204d63	168	if (!(vma->vm_flags & VM_CAN_NONLINEAR))
54cb8821 NP	169	goto out;
	170
	171	if (end <= start \|\| start < vma->vm_start \|\| end > vma->vm_end)
	172	goto out;
	173
	174	/* Must set VM_NONLINEAR before any pages are populated. */
	175	if (!(vma->vm_flags & VM_NONLINEAR)) {
	176	/* Don't need a nonlinear mapping, exit success */
	177	if (pgoff == linear_page_index(vma, start)) {
	178	err = 0;
	179	goto out;
	180	}
	181
	182	if (!has_write_lock) {
	183	up_read(&mm->mmap_sem);
	184	down_write(&mm->mmap_sem);
	185	has_write_lock = 1;
	186	goto retry;
	187	}
	188	mapping = vma->vm_file->f_mapping;
3ee6dafc MS	189	/*
	190	* page_mkclean doesn't work on nonlinear vmas, so if
	191	* dirty pages need to be accounted, emulate with linear
	192	* vmas.
	193	*/
	194	if (mapping_cap_account_dirty(mapping)) {
	195	unsigned long addr;
8a459e44	196	struct file *file = vma->vm_file;
3ee6dafc MS	197
3ee6dafc MS	198	flags &= MAP_NONBLOCK;
8a459e44 ON	199	get_file(file);
8a459e44 ON	200	addr = mmap_region(file, start, size,
5a6fe125	201	flags, vma->vm_flags, pgoff);
8a459e44	202	fput(file);
3ee6dafc MS	203	if (IS_ERR_VALUE(addr)) {
	204	err = addr;
	205	} else {
	206	BUG_ON(addr != start);
	207	err = 0;
	208	}
	209	goto out;
	210	}
54cb8821 NP	211	spin_lock(&mapping->i_mmap_lock);
	212	flush_dcache_mmap_lock(mapping);
	213	vma->vm_flags \|= VM_NONLINEAR;
	214	vma_prio_tree_remove(vma, &mapping->i_mmap);
	215	vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
	216	flush_dcache_mmap_unlock(mapping);
	217	spin_unlock(&mapping->i_mmap_lock);
	218	}
	219
ba470de4 RR	220	if (vma->vm_flags & VM_LOCKED) {
	221	/*
	222	* drop PG_Mlocked flag for over-mapped range
	223	*/
	224	unsigned int saved_flags = vma->vm_flags;
	225	munlock_vma_pages_range(vma, start, start + size);
	226	vma->vm_flags = saved_flags;
	227	}
	228
cddb8a5c	229	mmu_notifier_invalidate_range_start(mm, start, start + size);
d0217ac0	230	err = populate_range(mm, vma, start, size, pgoff);
cddb8a5c	231	mmu_notifier_invalidate_range_end(mm, start, start + size);
d0217ac0	232	if (!err && !(flags & MAP_NONBLOCK)) {
ba470de4 RR	233	if (vma->vm_flags & VM_LOCKED) {
	234	/*
	235	* might be mapping previously unmapped range of file
	236	*/
	237	mlock_vma_pages_range(vma, start, start + size);
	238	} else {
	239	if (unlikely(has_write_lock)) {
	240	downgrade_write(&mm->mmap_sem);
	241	has_write_lock = 0;
	242	}
	243	make_pages_present(start, start+size);
1da177e4	244	}
d0217ac0	245	}
1da177e4	246
54cb8821 NP	247	/*
	248	* We can't clear VM_NONLINEAR because we'd have to do
	249	* it after ->populate completes, and that would prevent
	250	* downgrading the lock. (Locks can't be upgraded).
	251	*/
1da177e4	252
54cb8821	253	out:
1da177e4 LT	254	if (likely(!has_write_lock))
	255	up_read(&mm->mmap_sem);
	256	else
	257	up_write(&mm->mmap_sem);
	258
	259	return err;
	260	}