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git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - mm/fremap.c
4 * Explicit pagetable population and nonlinear (random) mappings support.
6 * started by Ingo Molnar, Copyright (C) 2002, 2003
8 #include <linux/export.h>
9 #include <linux/backing-dev.h>
11 #include <linux/swap.h>
12 #include <linux/file.h>
13 #include <linux/mman.h>
14 #include <linux/pagemap.h>
15 #include <linux/swapops.h>
16 #include <linux/rmap.h>
17 #include <linux/syscalls.h>
18 #include <linux/mmu_notifier.h>
20 #include <asm/mmu_context.h>
21 #include <asm/cacheflush.h>
22 #include <asm/tlbflush.h>
26 static void zap_pte(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
27 unsigned long addr
, pte_t
*ptep
)
31 if (pte_present(pte
)) {
34 flush_cache_page(vma
, addr
, pte_pfn(pte
));
35 pte
= ptep_clear_flush(vma
, addr
, ptep
);
36 page
= vm_normal_page(vma
, addr
, pte
);
40 page_remove_rmap(page
);
41 page_cache_release(page
);
42 update_hiwater_rss(mm
);
43 dec_mm_counter(mm
, MM_FILEPAGES
);
47 free_swap_and_cache(pte_to_swp_entry(pte
));
48 pte_clear_not_present_full(mm
, addr
, ptep
, 0);
53 * Install a file pte to a given virtual memory address, release any
54 * previously existing mapping.
56 static int install_file_pte(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
57 unsigned long addr
, unsigned long pgoff
, pgprot_t prot
)
63 pte
= get_locked_pte(mm
, addr
, &ptl
);
68 zap_pte(mm
, vma
, addr
, pte
);
70 set_pte_at(mm
, addr
, pte
, pgoff_to_pte(pgoff
));
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).
78 pte_unmap_unlock(pte
, ptl
);
84 int generic_file_remap_pages(struct vm_area_struct
*vma
, unsigned long addr
,
85 unsigned long size
, pgoff_t pgoff
)
87 struct mm_struct
*mm
= vma
->vm_mm
;
91 err
= install_file_pte(mm
, vma
, addr
, pgoff
, vma
->vm_page_prot
);
102 EXPORT_SYMBOL(generic_file_remap_pages
);
105 * sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
106 * @start: start of the remapped virtual memory range
107 * @size: size of the remapped virtual memory range
108 * @prot: new protection bits of the range (see NOTE)
109 * @pgoff: to-be-mapped page of the backing store file
110 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
112 * sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
113 * (shared backing store file).
115 * This syscall works purely via pagetables, so it's the most efficient
116 * way to map the same (large) file into a given virtual window. Unlike
117 * mmap()/mremap() it does not create any new vmas. The new mappings are
118 * also safe across swapout.
120 * NOTE: the @prot parameter right now is ignored (but must be zero),
121 * and the vma's default protection is used. Arbitrary protections
122 * might be implemented in the future.
124 SYSCALL_DEFINE5(remap_file_pages
, unsigned long, start
, unsigned long, size
,
125 unsigned long, prot
, unsigned long, pgoff
, unsigned long, flags
)
127 struct mm_struct
*mm
= current
->mm
;
128 struct address_space
*mapping
;
129 struct vm_area_struct
*vma
;
131 int has_write_lock
= 0;
132 vm_flags_t vm_flags
= 0;
137 * Sanitize the syscall parameters:
139 start
= start
& PAGE_MASK
;
140 size
= size
& PAGE_MASK
;
142 /* Does the address range wrap, or is the span zero-sized? */
143 if (start
+ size
<= start
)
146 /* Does pgoff wrap? */
147 if (pgoff
+ (size
>> PAGE_SHIFT
) < pgoff
)
150 /* Can we represent this offset inside this architecture's pte's? */
151 #if PTE_FILE_MAX_BITS < BITS_PER_LONG
152 if (pgoff
+ (size
>> PAGE_SHIFT
) >= (1UL << PTE_FILE_MAX_BITS
))
156 /* We need down_write() to change vma->vm_flags. */
157 down_read(&mm
->mmap_sem
);
159 vma
= find_vma(mm
, start
);
162 * Make sure the vma is shared, that it supports prefaulting,
163 * and that the remapped range is valid and fully within
164 * the single existing vma.
166 if (!vma
|| !(vma
->vm_flags
& VM_SHARED
))
169 if (!vma
->vm_ops
|| !vma
->vm_ops
->remap_pages
)
172 if (start
< vma
->vm_start
|| start
+ size
> vma
->vm_end
)
175 /* Must set VM_NONLINEAR before any pages are populated. */
176 if (!(vma
->vm_flags
& VM_NONLINEAR
)) {
178 * vm_private_data is used as a swapout cursor
179 * in a VM_NONLINEAR vma.
181 if (vma
->vm_private_data
)
184 /* Don't need a nonlinear mapping, exit success */
185 if (pgoff
== linear_page_index(vma
, start
)) {
190 if (!has_write_lock
) {
192 up_read(&mm
->mmap_sem
);
193 down_write(&mm
->mmap_sem
);
197 mapping
= vma
->vm_file
->f_mapping
;
199 * page_mkclean doesn't work on nonlinear vmas, so if
200 * dirty pages need to be accounted, emulate with linear
203 if (mapping_cap_account_dirty(mapping
)) {
205 struct file
*file
= get_file(vma
->vm_file
);
207 vm_flags
= vma
->vm_flags
;
208 if (!(flags
& MAP_NONBLOCK
))
209 vm_flags
|= VM_POPULATE
;
210 addr
= mmap_region(file
, start
, size
, vm_flags
, pgoff
);
212 if (IS_ERR_VALUE(addr
)) {
215 BUG_ON(addr
!= start
);
220 mutex_lock(&mapping
->i_mmap_mutex
);
221 flush_dcache_mmap_lock(mapping
);
222 vma
->vm_flags
|= VM_NONLINEAR
;
223 vma_interval_tree_remove(vma
, &mapping
->i_mmap
);
224 vma_nonlinear_insert(vma
, &mapping
->i_mmap_nonlinear
);
225 flush_dcache_mmap_unlock(mapping
);
226 mutex_unlock(&mapping
->i_mmap_mutex
);
229 if (!(flags
& MAP_NONBLOCK
) && !(vma
->vm_flags
& VM_POPULATE
)) {
232 vma
->vm_flags
|= VM_POPULATE
;
235 if (vma
->vm_flags
& VM_LOCKED
) {
237 * drop PG_Mlocked flag for over-mapped range
241 vm_flags
= vma
->vm_flags
;
242 munlock_vma_pages_range(vma
, start
, start
+ size
);
243 vma
->vm_flags
= vm_flags
;
246 mmu_notifier_invalidate_range_start(mm
, start
, start
+ size
);
247 err
= vma
->vm_ops
->remap_pages(vma
, start
, size
, pgoff
);
248 mmu_notifier_invalidate_range_end(mm
, start
, start
+ size
);
251 * We can't clear VM_NONLINEAR because we'd have to do
252 * it after ->populate completes, and that would prevent
253 * downgrading the lock. (Locks can't be upgraded).
258 vm_flags
= vma
->vm_flags
;
259 if (likely(!has_write_lock
))
260 up_read(&mm
->mmap_sem
);
262 up_write(&mm
->mmap_sem
);
263 if (!err
&& ((vm_flags
& VM_LOCKED
) || !(flags
& MAP_NONBLOCK
)))
264 mm_populate(start
, size
);