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/*
* linux/mm/memory.c
*
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
*/
/*
* demand-loading started 01.12.91 - seems it is high on the list of
* things wanted, and it should be easy to implement. - Linus
*/
/*
* Ok, demand-loading was easy, shared pages a little bit tricker. Shared
* pages started 02.12.91, seems to work. - Linus.
*
* Tested sharing by executing about 30 /bin/sh: under the old kernel it
* would have taken more than the 6M I have free, but it worked well as
* far as I could see.
*
* Also corrected some "invalidate()"s - I wasn't doing enough of them.
*/
/*
* Real VM (paging to/from disk) started 18.12.91. Much more work and
* thought has to go into this. Oh, well..
* 19.12.91 - works, somewhat. Sometimes I get faults, don't know why.
* Found it. Everything seems to work now.
* 20.12.91 - Ok, making the swap-device changeable like the root.
*/
/*
* 05.04.94 - Multi-page memory management added for v1.1.
* Idea by Alex Bligh (alex@cconcepts.co.uk)
*
* 16.07.99 - Support of BIGMEM added by Gerhard Wichert, Siemens AG
* (Gerhard.Wichert@pdb.siemens.de)
*/
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/smp_lock.h>
#include <linux/swapctl.h>
#include <linux/iobuf.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <asm/pgalloc.h>
#include <asm/uaccess.h>
#include <asm/tlb.h>
unsigned long max_mapnr;
unsigned long num_physpages;
void * high_memory;
struct page *highmem_start_page;
/*
* We special-case the C-O-W ZERO_PAGE, because it's such
* a common occurrence (no need to read the page to know
* that it's zero - better for the cache and memory subsystem).
*/
static inline void copy_cow_page(struct page * from, struct page * to, unsigned long address)
{
if (from == ZERO_PAGE(address)) {
clear_user_highpage(to, address);
return;
}
copy_user_highpage(to, from, address);
}
mem_map_t * mem_map;
/*
* Called by TLB shootdown
*/
void __free_pte(pte_t pte)
{
struct page *page = pte_page(pte);
if ((!VALID_PAGE(page)) || PageReserved(page))
return;
if (pte_dirty(pte))
set_page_dirty(page);
free_page_and_swap_cache(page);
}
/*
* Note: this doesn't free the actual pages themselves. That
* has been handled earlier when unmapping all the memory regions.
*/
static inline void free_one_pmd(pmd_t * dir)
{
pte_t * pte;
if (pmd_none(*dir))
return;
if (pmd_bad(*dir)) {
pmd_ERROR(*dir);
pmd_clear(dir);
return;
}
pte = pte_offset(dir, 0);
pmd_clear(dir);
pte_free(pte);
}
static inline void free_one_pgd(pgd_t * dir)
{
int j;
pmd_t * pmd;
if (pgd_none(*dir))
return;
if (pgd_bad(*dir)) {
pgd_ERROR(*dir);
pgd_clear(dir);
return;
}
pmd = pmd_offset(dir, 0);
pgd_clear(dir);
for (j = 0; j < PTRS_PER_PMD ; j++) {
prefetchw(pmd+j+(PREFETCH_STRIDE/16));
free_one_pmd(pmd+j);
}
pmd_free(pmd);
}
/* Low and high watermarks for page table cache.
The system should try to have pgt_water[0] <= cache elements <= pgt_water[1]
*/
int pgt_cache_water[2] = { 25, 50 };
/* Returns the number of pages freed */
int check_pgt_cache(void)
{
return do_check_pgt_cache(pgt_cache_water[0], pgt_cache_water[1]);
}
/*
* This function clears all user-level page tables of a process - this
* is needed by execve(), so that old pages aren't in the way.
*/
void clear_page_tables(struct mm_struct *mm, unsigned long first, int nr)
{
pgd_t * page_dir = mm->pgd;
spin_lock(&mm->page_table_lock);
page_dir += first;
do {
free_one_pgd(page_dir);
page_dir++;
} while (--nr);
spin_unlock(&mm->page_table_lock);
/* keep the page table cache within bounds */
check_pgt_cache();
}
#define PTE_TABLE_MASK ((PTRS_PER_PTE-1) * sizeof(pte_t))
#define PMD_TABLE_MASK ((PTRS_PER_PMD-1) * sizeof(pmd_t))
/*
* copy one vm_area from one task to the other. Assumes the page tables
* already present in the new task to be cleared in the whole range
* covered by this vma.
*
* 08Jan98 Merged into one routine from several inline routines to reduce
* variable count and make things faster. -jj
*
* dst->page_table_lock is held on entry and exit,
* but may be dropped within pmd_alloc() and pte_alloc().
*/
int copy_page_range(struct mm_struct *dst, struct mm_struct *src,
struct vm_area_struct *vma)
{
pgd_t * src_pgd, * dst_pgd;
unsigned long address = vma->vm_start;
unsigned long end = vma->vm_end;
unsigned long cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
src_pgd = pgd_offset(src, address)-1;
dst_pgd = pgd_offset(dst, address)-1;
for (;;) {
pmd_t * src_pmd, * dst_pmd;
src_pgd++; dst_pgd++;
/* copy_pmd_range */
if (pgd_none(*src_pgd))
goto skip_copy_pmd_range;
if (pgd_bad(*src_pgd)) {
pgd_ERROR(*src_pgd);
pgd_clear(src_pgd);
skip_copy_pmd_range: address = (address + PGDIR_SIZE) & PGDIR_MASK;
if (!address || (address >= end))
goto out;
continue;
}
src_pmd = pmd_offset(src_pgd, address);
dst_pmd = pmd_alloc(dst, dst_pgd, address);
if (!dst_pmd)
goto nomem;
do {
pte_t * src_pte, * dst_pte;
/* copy_pte_range */
if (pmd_none(*src_pmd))
goto skip_copy_pte_range;
if (pmd_bad(*src_pmd)) {
pmd_ERROR(*src_pmd);
pmd_clear(src_pmd);
skip_copy_pte_range: address = (address + PMD_SIZE) & PMD_MASK;
if (address >= end)
goto out;
goto cont_copy_pmd_range;
}
src_pte = pte_offset(src_pmd, address);
dst_pte = pte_alloc(dst, dst_pmd, address);
if (!dst_pte)
goto nomem;
spin_lock(&src->page_table_lock);
do {
pte_t pte = *src_pte;
struct page *ptepage;
/* copy_one_pte */
if (pte_none(pte))
goto cont_copy_pte_range_noset;
if (!pte_present(pte)) {
swap_duplicate(pte_to_swp_entry(pte));
goto cont_copy_pte_range;
}
ptepage = pte_page(pte);
if ((!VALID_PAGE(ptepage)) ||
PageReserved(ptepage))
goto cont_copy_pte_range;
/* If it's a COW mapping, write protect it both in the parent and the child */
if (cow && pte_write(pte)) {
ptep_set_wrprotect(src_pte);
pte = *src_pte;
}
/* If it's a shared mapping, mark it clean in the child */
if (vma->vm_flags & VM_SHARED)
pte = pte_mkclean(pte);
pte = pte_mkold(pte);
get_page(ptepage);
dst->rss++;
cont_copy_pte_range: set_pte(dst_pte, pte);
cont_copy_pte_range_noset: address += PAGE_SIZE;
if (address >= end)
goto out_unlock;
src_pte++;
dst_pte++;
} while ((unsigned long)src_pte & PTE_TABLE_MASK);
spin_unlock(&src->page_table_lock);
cont_copy_pmd_range: src_pmd++;
dst_pmd++;
} while ((unsigned long)src_pmd & PMD_TABLE_MASK);
}
out_unlock:
spin_unlock(&src->page_table_lock);
out:
return 0;
nomem:
return -ENOMEM;
}
/*
* Return indicates whether a page was freed so caller can adjust rss
*/
static inline void forget_pte(pte_t page)
{
if (!pte_none(page)) {
printk("forget_pte: old mapping existed!\n");
BUG();
}
}
static inline int zap_pte_range(mmu_gather_t *tlb, pmd_t * pmd, unsigned long address, unsigned long size)
{
unsigned long offset;
pte_t * ptep;
int freed = 0;
if (pmd_none(*pmd))
return 0;
if (pmd_bad(*pmd)) {
pmd_ERROR(*pmd);
pmd_clear(pmd);
return 0;
}
ptep = pte_offset(pmd, address);
offset = address & ~PMD_MASK;
if (offset + size > PMD_SIZE)
size = PMD_SIZE - offset;
size &= PAGE_MASK;
for (offset=0; offset < size; ptep++, offset += PAGE_SIZE) {
pte_t pte = *ptep;
if (pte_none(pte))
continue;
if (pte_present(pte)) {
struct page *page = pte_page(pte);
if (VALID_PAGE(page) && !PageReserved(page))
freed ++;
/* This will eventually call __free_pte on the pte. */
tlb_remove_page(tlb, ptep, address + offset);
} else {
free_swap_and_cache(pte_to_swp_entry(pte));
pte_clear(ptep);
}
}
return freed;
}
static inline int zap_pmd_range(mmu_gather_t *tlb, pgd_t * dir, unsigned long address, unsigned long size)
{
pmd_t * pmd;
unsigned long end;
int freed;
if (pgd_none(*dir))
return 0;
if (pgd_bad(*dir)) {
pgd_ERROR(*dir);
pgd_clear(dir);
return 0;
}
pmd = pmd_offset(dir, address);
end = address + size;
if (end > ((address + PGDIR_SIZE) & PGDIR_MASK))
end = ((address + PGDIR_SIZE) & PGDIR_MASK);
freed = 0;
do {
freed += zap_pte_range(tlb, pmd, address, end - address);
address = (address + PMD_SIZE) & PMD_MASK;
pmd++;
} while (address < end);
return freed;
}
/*
* remove user pages in a given range.
*/
void zap_page_range(struct mm_struct *mm, unsigned long address, unsigned long size)
{
mmu_gather_t *tlb;
pgd_t * dir;
unsigned long start = address, end = address + size;
int freed = 0;
dir = pgd_offset(mm, address);
/*
* This is a long-lived spinlock. That's fine.
* There's no contention, because the page table
* lock only protects against kswapd anyway, and
* even if kswapd happened to be looking at this
* process we _want_ it to get stuck.
*/
if (address >= end)
BUG();
spin_lock(&mm->page_table_lock);
flush_cache_range(mm, address, end);
tlb = tlb_gather_mmu(mm);
do {
freed += zap_pmd_range(tlb, dir, address, end - address);
address = (address + PGDIR_SIZE) & PGDIR_MASK;
dir++;
} while (address && (address < end));
/* this will flush any remaining tlb entries */
tlb_finish_mmu(tlb, start, end);
/*
* Update rss for the mm_struct (not necessarily current->mm)
* Notice that rss is an unsigned long.
*/
if (mm->rss > freed)
mm->rss -= freed;
else
mm->rss = 0;
spin_unlock(&mm->page_table_lock);
}
/*
* Do a quick page-table lookup for a single page.
*/
static struct page * follow_page(struct mm_struct *mm, unsigned long address, int write)
{
pgd_t *pgd;
pmd_t *pmd;
pte_t *ptep, pte;
pgd = pgd_offset(mm, address);
if (pgd_none(*pgd) || pgd_bad(*pgd))
goto out;
pmd = pmd_offset(pgd, address);
if (pmd_none(*pmd) || pmd_bad(*pmd))
goto out;
ptep = pte_offset(pmd, address);
if (!ptep)
goto out;
pte = *ptep;
if (pte_present(pte)) {
if (!write ||
(pte_write(pte) && pte_dirty(pte)))
return pte_page(pte);
}
out:
return 0;
}
/*
* Given a physical address, is there a useful struct page pointing to
* it? This may become more complex in the future if we start dealing
* with IO-aperture pages in kiobufs.
*/
static inline struct page * get_page_map(struct page *page)
{
if (!VALID_PAGE(page))
return 0;
return page;
}
/*
* Please read Documentation/cachetlb.txt before using this function,
* accessing foreign memory spaces can cause cache coherency problems.
*
* Accessing a VM_IO area is even more dangerous, therefore the function
* fails if pages is != NULL and a VM_IO area is found.
*/
int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start,
int len, int write, int force, struct page **pages, struct vm_area_struct **vmas)
{
int i;
unsigned int flags;
/*
* Require read or write permissions.
* If 'force' is set, we only require the "MAY" flags.
*/
flags = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
i = 0;
do {
struct vm_area_struct * vma;
vma = find_extend_vma(mm, start);
if ( !vma || (pages && vma->vm_flags & VM_IO) || !(flags & vma->vm_flags) )
return i ? : -EFAULT;
spin_lock(&mm->page_table_lock);
do {
struct page *map;
while (!(map = follow_page(mm, start, write))) {
spin_unlock(&mm->page_table_lock);
switch (handle_mm_fault(mm, vma, start, write)) {
case 1:
tsk->min_flt++;
break;
case 2:
tsk->maj_flt++;
break;
case 0:
if (i) return i;
return -EFAULT;
default:
if (i) return i;
return -ENOMEM;
}
spin_lock(&mm->page_table_lock);
}
if (pages) {
pages[i] = get_page_map(map);
/* FIXME: call the correct function,
* depending on the type of the found page
*/
if (!pages[i])
goto bad_page;
page_cache_get(pages[i]);
}
if (vmas)
vmas[i] = vma;
i++;
start += PAGE_SIZE;
len--;
} while(len && start < vma->vm_end);
spin_unlock(&mm->page_table_lock);
} while(len);
out:
return i;
/*
* We found an invalid page in the VMA. Release all we have
* so far and fail.
*/
bad_page:
spin_unlock(&mm->page_table_lock);
while (i--)
page_cache_release(pages[i]);
i = -EFAULT;
goto out;
}
/*
* Force in an entire range of pages from the current process's user VA,
* and pin them in physical memory.
*/
#define dprintk(x...)
int map_user_kiobuf(int rw, struct kiobuf *iobuf, unsigned long va, size_t len)
{
int pgcount, err;
struct mm_struct * mm;
/* Make sure the iobuf is not already mapped somewhere. */
if (iobuf->nr_pages)
return -EINVAL;
mm = current->mm;
dprintk ("map_user_kiobuf: begin\n");
pgcount = (va + len + PAGE_SIZE - 1)/PAGE_SIZE - va/PAGE_SIZE;
/* mapping 0 bytes is not permitted */
if (!pgcount) BUG();
err = expand_kiobuf(iobuf, pgcount);
if (err)
return err;
iobuf->locked = 0;
iobuf->offset = va & (PAGE_SIZE-1);
iobuf->length = len;
/* Try to fault in all of the necessary pages */
down_read(&mm->mmap_sem);
/* rw==READ means read from disk, write into memory area */
err = get_user_pages(current, mm, va, pgcount,
(rw==READ), 0, iobuf->maplist, NULL);
up_read(&mm->mmap_sem);
if (err < 0) {
unmap_kiobuf(iobuf);
dprintk ("map_user_kiobuf: end %d\n", err);
return err;
}
iobuf->nr_pages = err;
while (pgcount--) {
/* FIXME: flush superflous for rw==READ,
* probably wrong function for rw==WRITE
*/
flush_dcache_page(iobuf->maplist[pgcount]);
}
dprintk ("map_user_kiobuf: end OK\n");
return 0;
}
/*
* Mark all of the pages in a kiobuf as dirty
*
* We need to be able to deal with short reads from disk: if an IO error
* occurs, the number of bytes read into memory may be less than the
* size of the kiobuf, so we have to stop marking pages dirty once the
* requested byte count has been reached.
*/
void mark_dirty_kiobuf(struct kiobuf *iobuf, int bytes)
{
int index, offset, remaining;
struct page *page;
index = iobuf->offset >> PAGE_SHIFT;
offset = iobuf->offset & ~PAGE_MASK;
remaining = bytes;
if (remaining > iobuf->length)
remaining = iobuf->length;
while (remaining > 0 && index < iobuf->nr_pages) {
page = iobuf->maplist[index];
if (!PageReserved(page))
SetPageDirty(page);
remaining -= (PAGE_SIZE - offset);
offset = 0;
index++;
}
}
/*
* Unmap all of the pages referenced by a kiobuf. We release the pages,
* and unlock them if they were locked.
*/
void unmap_kiobuf (struct kiobuf *iobuf)
{
int i;
struct page *map;
for (i = 0; i < iobuf->nr_pages; i++) {
map = iobuf->maplist[i];
if (map) {
if (iobuf->locked)
UnlockPage(map);
/* FIXME: cache flush missing for rw==READ
* FIXME: call the correct reference counting function
*/
page_cache_release(map);
}
}
iobuf->nr_pages = 0;
iobuf->locked = 0;
}
/*
* Lock down all of the pages of a kiovec for IO.
*
* If any page is mapped twice in the kiovec, we return the error -EINVAL.
*
* The optional wait parameter causes the lock call to block until all
* pages can be locked if set. If wait==0, the lock operation is
* aborted if any locked pages are found and -EAGAIN is returned.
*/
int lock_kiovec(int nr, struct kiobuf *iovec[], int wait)
{
struct kiobuf *iobuf;
int i, j;
struct page *page, **ppage;
int doublepage = 0;
int repeat = 0;
repeat:
for (i = 0; i < nr; i++) {
iobuf = iovec[i];
if (iobuf->locked)
continue;
ppage = iobuf->maplist;
for (j = 0; j < iobuf->nr_pages; ppage++, j++) {
page = *ppage;
if (!page)
continue;
if (TryLockPage(page)) {
while (j--) {
struct page *tmp = *--ppage;
if (tmp)
UnlockPage(tmp);
}
goto retry;
}
}
iobuf->locked = 1;
}
return 0;
retry:
/*
* We couldn't lock one of the pages. Undo the locking so far,
* wait on the page we got to, and try again.
*/
unlock_kiovec(nr, iovec);
if (!wait)
return -EAGAIN;
/*
* Did the release also unlock the page we got stuck on?
*/
if (!PageLocked(page)) {
/*
* If so, we may well have the page mapped twice
* in the IO address range. Bad news. Of
* course, it _might_ just be a coincidence,
* but if it happens more than once, chances
* are we have a double-mapped page.
*/
if (++doublepage >= 3)
return -EINVAL;
/* Try again... */
wait_on_page(page);
}
if (++repeat < 16)
goto repeat;
return -EAGAIN;
}
/*
* Unlock all of the pages of a kiovec after IO.
*/
int unlock_kiovec(int nr, struct kiobuf *iovec[])
{
struct kiobuf *iobuf;
int i, j;
struct page *page, **ppage;
for (i = 0; i < nr; i++) {
iobuf = iovec[i];
if (!iobuf->locked)
continue;
iobuf->locked = 0;
ppage = iobuf->maplist;
for (j = 0; j < iobuf->nr_pages; ppage++, j++) {
page = *ppage;
if (!page)
continue;
UnlockPage(page);
}
}
return 0;
}
static inline void zeromap_pte_range(pte_t * pte, unsigned long address,
unsigned long size, pgprot_t prot)
{
unsigned long end;
address &= ~PMD_MASK;
end = address + size;
if (end > PMD_SIZE)
end = PMD_SIZE;
do {
pte_t zero_pte = pte_wrprotect(mk_pte(ZERO_PAGE(address), prot));
pte_t oldpage = ptep_get_and_clear(pte);
set_pte(pte, zero_pte);
forget_pte(oldpage);
address += PAGE_SIZE;
pte++;
} while (address && (address < end));
}
static inline int zeromap_pmd_range(struct mm_struct *mm, pmd_t * pmd, unsigned long address,
unsigned long size, pgprot_t prot)
{
unsigned long end;
address &= ~PGDIR_MASK;
end = address + size;
if (end > PGDIR_SIZE)
end = PGDIR_SIZE;
do {
pte_t * pte = pte_alloc(mm, pmd, address);
if (!pte)
return -ENOMEM;
zeromap_pte_range(pte, address, end - address, prot);
address = (address + PMD_SIZE) & PMD_MASK;
pmd++;
} while (address && (address < end));
return 0;
}
int zeromap_page_range(unsigned long address, unsigned long size, pgprot_t prot)
{
int error = 0;
pgd_t * dir;
unsigned long beg = address;
unsigned long end = address + size;
struct mm_struct *mm = current->mm;
dir = pgd_offset(mm, address);
flush_cache_range(mm, beg, end);
if (address >= end)
BUG();
spin_lock(&mm->page_table_lock);
do {
pmd_t *pmd = pmd_alloc(mm, dir, address);
error = -ENOMEM;
if (!pmd)
break;
error = zeromap_pmd_range(mm, pmd, address, end - address, prot);
if (error)
break;
address = (address + PGDIR_SIZE) & PGDIR_MASK;
dir++;
} while (address && (address < end));
spin_unlock(&mm->page_table_lock);
flush_tlb_range(mm, beg, end);
return error;
}
/*
* maps a range of physical memory into the requested pages. the old
* mappings are removed. any references to nonexistent pages results
* in null mappings (currently treated as "copy-on-access")
*/
static inline void remap_pte_range(pte_t * pte, unsigned long address, unsigned long size,
unsigned long phys_addr, pgprot_t prot)
{
unsigned long end;
address &= ~PMD_MASK;
end = address + size;
if (end > PMD_SIZE)
end = PMD_SIZE;
do {
struct page *page;
pte_t oldpage;
oldpage = ptep_get_and_clear(pte);
page = virt_to_page(__va(phys_addr));
if ((!VALID_PAGE(page)) || PageReserved(page))
set_pte(pte, mk_pte_phys(phys_addr, prot));
forget_pte(oldpage);
address += PAGE_SIZE;
phys_addr += PAGE_SIZE;
pte++;
} while (address && (address < end));
}
static inline int remap_pmd_range(struct mm_struct *mm, pmd_t * pmd, unsigned long address, unsigned long size,
unsigned long phys_addr, pgprot_t prot)
{
unsigned long end;
address &= ~PGDIR_MASK;
end = address + size;
if (end > PGDIR_SIZE)
end = PGDIR_SIZE;
phys_addr -= address;
do {
pte_t * pte = pte_alloc(mm, pmd, address);
if (!pte)
return -ENOMEM;
remap_pte_range(pte, address, end - address, address + phys_addr, prot);
address = (address + PMD_SIZE) & PMD_MASK;
pmd++;
} while (address && (address < end));
return 0;
}
/* Note: this is only safe if the mm semaphore is held when called. */
int remap_page_range(unsigned long from, unsigned long phys_addr, unsigned long size, pgprot_t prot)
{
int error = 0;
pgd_t * dir;
unsigned long beg = from;
unsigned long end = from + size;
struct mm_struct *mm = current->mm;
phys_addr -= from;
dir = pgd_offset(mm, from);
flush_cache_range(mm, beg, end);
if (from >= end)
BUG();
spin_lock(&mm->page_table_lock);
do {
pmd_t *pmd = pmd_alloc(mm, dir, from);
error = -ENOMEM;
if (!pmd)
break;
error = remap_pmd_range(mm, pmd, from, end - from, phys_addr + from, prot);
if (error)
break;
from = (from + PGDIR_SIZE) & PGDIR_MASK;
dir++;
} while (from && (from < end));
spin_unlock(&mm->page_table_lock);
flush_tlb_range(mm, beg, end);
return error;
}
/*
* Establish a new mapping:
* - flush the old one
* - update the page tables
* - inform the TLB about the new one
*
* We hold the mm semaphore for reading and vma->vm_mm->page_table_lock
*/
static inline void establish_pte(struct vm_area_struct * vma, unsigned long address, pte_t *page_table, pte_t entry)
{
set_pte(page_table, entry);
flush_tlb_page(vma, address);
update_mmu_cache(vma, address, entry);
}
/*
* We hold the mm semaphore for reading and vma->vm_mm->page_table_lock
*/
static inline void break_cow(struct vm_area_struct * vma, struct page * new_page, unsigned long address,
pte_t *page_table)
{
flush_page_to_ram(new_page);
flush_cache_page(vma, address);
establish_pte(vma, address, page_table, pte_mkwrite(pte_mkdirty(mk_pte(new_page, vma->vm_page_prot))));
}
/*
* This routine handles present pages, when users try to write
* to a shared page. It is done by copying the page to a new address
* and decrementing the shared-page counter for the old page.
*
* Goto-purists beware: the only reason for goto's here is that it results
* in better assembly code.. The "default" path will see no jumps at all.
*
* Note that this routine assumes that the protection checks have been
* done by the caller (the low-level page fault routine in most cases).
* Thus we can safely just mark it writable once we've done any necessary
* COW.
*
* We also mark the page dirty at this point even though the page will
* change only once the write actually happens. This avoids a few races,
* and potentially makes it more efficient.
*
* We hold the mm semaphore and the page_table_lock on entry and exit
* with the page_table_lock released.
*/
static int do_wp_page(struct mm_struct *mm, struct vm_area_struct * vma,
unsigned long address, pte_t *page_table, pte_t pte)
{
struct page *old_page, *new_page;
old_page = pte_page(pte);
if (!VALID_PAGE(old_page))
goto bad_wp_page;
if (!TryLockPage(old_page)) {
int reuse = can_share_swap_page(old_page);
unlock_page(old_page);
if (reuse) {
flush_cache_page(vma, address);
establish_pte(vma, address, page_table, pte_mkyoung(pte_mkdirty(pte_mkwrite(pte))));
spin_unlock(&mm->page_table_lock);
return 1; /* Minor fault */
}
}
/*
* Ok, we need to copy. Oh, well..
*/
page_cache_get(old_page);
spin_unlock(&mm->page_table_lock);
new_page = alloc_page(GFP_HIGHUSER);
if (!new_page)
goto no_mem;
copy_cow_page(old_page,new_page,address);
/*
* Re-check the pte - we dropped the lock
*/
spin_lock(&mm->page_table_lock);
if (pte_same(*page_table, pte)) {
if (PageReserved(old_page))
++mm->rss;
break_cow(vma, new_page, address, page_table);
lru_cache_add(new_page);
/* Free the old page.. */
new_page = old_page;
}
spin_unlock(&mm->page_table_lock);
page_cache_release(new_page);
page_cache_release(old_page);
return 1; /* Minor fault */
bad_wp_page:
spin_unlock(&mm->page_table_lock);
printk("do_wp_page: bogus page at address %08lx (page 0x%lx)\n",address,(unsigned long)old_page);
return -1;
no_mem:
page_cache_release(old_page);
return -1;
}
static void vmtruncate_list(struct vm_area_struct *mpnt, unsigned long pgoff)
{
do {
struct mm_struct *mm = mpnt->vm_mm;
unsigned long start = mpnt->vm_start;
unsigned long end = mpnt->vm_end;
unsigned long len = end - start;
unsigned long diff;
/* mapping wholly truncated? */
if (mpnt->vm_pgoff >= pgoff) {
zap_page_range(mm, start, len);
continue;
}
/* mapping wholly unaffected? */
len = len >> PAGE_SHIFT;
diff = pgoff - mpnt->vm_pgoff;
if (diff >= len)
continue;
/* Ok, partially affected.. */
start += diff << PAGE_SHIFT;
len = (len - diff) << PAGE_SHIFT;
zap_page_range(mm, start, len);
} while ((mpnt = mpnt->vm_next_share) != NULL);
}
/*
* Handle all mappings that got truncated by a "truncate()"
* system call.
*
* NOTE! We have to be ready to update the memory sharing
* between the file and the memory map for a potential last
* incomplete page. Ugly, but necessary.
*/
int vmtruncate(struct inode * inode, loff_t offset)
{
unsigned long pgoff;
struct address_space *mapping = inode->i_mapping;
unsigned long limit;
if (inode->i_size < offset)
goto do_expand;
inode->i_size = offset;
spin_lock(&mapping->i_shared_lock);
if (!mapping->i_mmap && !mapping->i_mmap_shared)
goto out_unlock;
pgoff = (offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (mapping->i_mmap != NULL)
vmtruncate_list(mapping->i_mmap, pgoff);
if (mapping->i_mmap_shared != NULL)
vmtruncate_list(mapping->i_mmap_shared, pgoff);
out_unlock:
spin_unlock(&mapping->i_shared_lock);
truncate_inode_pages(mapping, offset);
goto out_truncate;
do_expand:
limit = current->rlim[RLIMIT_FSIZE].rlim_cur;
if (limit != RLIM_INFINITY && offset > limit)
goto out_sig;
if (offset > inode->i_sb->s_maxbytes)
goto out;
inode->i_size = offset;
out_truncate:
if (inode->i_op && inode->i_op->truncate) {
lock_kernel();
inode->i_op->truncate(inode);
unlock_kernel();
}
return 0;
out_sig:
send_sig(SIGXFSZ, current, 0);
out:
return -EFBIG;
}
/*
* Primitive swap readahead code. We simply read an aligned block of
* (1 << page_cluster) entries in the swap area. This method is chosen
* because it doesn't cost us any seek time. We also make sure to queue
* the 'original' request together with the readahead ones...
*/
void swapin_readahead(swp_entry_t entry)
{
int i, num;
struct page *new_page;
unsigned long offset;
/*
* Get the number of handles we should do readahead io to.
*/
num = valid_swaphandles(entry, &offset);
for (i = 0; i < num; offset++, i++) {
/* Ok, do the async read-ahead now */
new_page = read_swap_cache_async(SWP_ENTRY(SWP_TYPE(entry), offset));
if (!new_page)
break;
page_cache_release(new_page);
}
return;
}
/*
* We hold the mm semaphore and the page_table_lock on entry and
* should release the pagetable lock on exit..
*/
static int do_swap_page(struct mm_struct * mm,
struct vm_area_struct * vma, unsigned long address,
pte_t * page_table, pte_t orig_pte, int write_access)
{
struct page *page;
swp_entry_t entry = pte_to_swp_entry(orig_pte);
pte_t pte;
int ret = 1;
spin_unlock(&mm->page_table_lock);
page = lookup_swap_cache(entry);
if (!page) {
swapin_readahead(entry);
page = read_swap_cache_async(entry);
if (!page) {
/*
* Back out if somebody else faulted in this pte while
* we released the page table lock.
*/
int retval;
spin_lock(&mm->page_table_lock);
retval = pte_same(*page_table, orig_pte) ? -1 : 1;
spin_unlock(&mm->page_table_lock);
return retval;
}
/* Had to read the page from swap area: Major fault */
ret = 2;
}
mark_page_accessed(page);
lock_page(page);
/*
* Back out if somebody else faulted in this pte while we
* released the page table lock.
*/
spin_lock(&mm->page_table_lock);
if (!pte_same(*page_table, orig_pte)) {
spin_unlock(&mm->page_table_lock);
unlock_page(page);
page_cache_release(page);
return 1;
}
/* The page isn't present yet, go ahead with the fault. */
swap_free(entry);
if (vm_swap_full())
remove_exclusive_swap_page(page);
mm->rss++;
pte = mk_pte(page, vma->vm_page_prot);
if (write_access && can_share_swap_page(page))
pte = pte_mkdirty(pte_mkwrite(pte));
unlock_page(page);
flush_page_to_ram(page);
flush_icache_page(vma, page);
set_pte(page_table, pte);
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, address, pte);
spin_unlock(&mm->page_table_lock);
return ret;
}
/*
* We are called with the MM semaphore and page_table_lock
* spinlock held to protect against concurrent faults in
* multithreaded programs.
*/
static int do_anonymous_page(struct mm_struct * mm, struct vm_area_struct * vma, pte_t *page_table, int write_access, unsigned long addr)
{
pte_t entry;
/* Read-only mapping of ZERO_PAGE. */
entry = pte_wrprotect(mk_pte(ZERO_PAGE(addr), vma->vm_page_prot));
/* ..except if it's a write access */
if (write_access) {
struct page *page;
/* Allocate our own private page. */
spin_unlock(&mm->page_table_lock);
page = alloc_page(GFP_HIGHUSER);
if (!page)
goto no_mem;
clear_user_highpage(page, addr);
spin_lock(&mm->page_table_lock);
if (!pte_none(*page_table)) {
page_cache_release(page);
spin_unlock(&mm->page_table_lock);
return 1;
}
mm->rss++;
flush_page_to_ram(page);
entry = pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
lru_cache_add(page);
mark_page_accessed(page);
}
set_pte(page_table, entry);
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, addr, entry);
spin_unlock(&mm->page_table_lock);
return 1; /* Minor fault */
no_mem:
return -1;
}
/*
* do_no_page() tries to create a new page mapping. It aggressively
* tries to share with existing pages, but makes a separate copy if
* the "write_access" parameter is true in order to avoid the next
* page fault.
*
* As this is called only for pages that do not currently exist, we
* do not need to flush old virtual caches or the TLB.
*
* This is called with the MM semaphore held and the page table
* spinlock held. Exit with the spinlock released.
*/
static int do_no_page(struct mm_struct * mm, struct vm_area_struct * vma,
unsigned long address, int write_access, pte_t *page_table)
{
struct page * new_page;
pte_t entry;
if (!vma->vm_ops || !vma->vm_ops->nopage)
return do_anonymous_page(mm, vma, page_table, write_access, address);
spin_unlock(&mm->page_table_lock);
new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, 0);
if (new_page == NULL) /* no page was available -- SIGBUS */
return 0;
if (new_page == NOPAGE_OOM)
return -1;
/*
* Should we do an early C-O-W break?
*/
if (write_access && !(vma->vm_flags & VM_SHARED)) {
struct page * page = alloc_page(GFP_HIGHUSER);
if (!page) {
page_cache_release(new_page);
return -1;
}
copy_user_highpage(page, new_page, address);
page_cache_release(new_page);
lru_cache_add(page);
new_page = page;
}
spin_lock(&mm->page_table_lock);
/*
* This silly early PAGE_DIRTY setting removes a race
* due to the bad i386 page protection. But it's valid
* for other architectures too.
*
* Note that if write_access is true, we either now have
* an exclusive copy of the page, or this is a shared mapping,
* so we can make it writable and dirty to avoid having to
* handle that later.
*/
/* Only go through if we didn't race with anybody else... */
if (pte_none(*page_table)) {
++mm->rss;
flush_page_to_ram(new_page);
flush_icache_page(vma, new_page);
entry = mk_pte(new_page, vma->vm_page_prot);
if (write_access)
entry = pte_mkwrite(pte_mkdirty(entry));
set_pte(page_table, entry);
} else {
/* One of our sibling threads was faster, back out. */
page_cache_release(new_page);
spin_unlock(&mm->page_table_lock);
return 1;
}
/* no need to invalidate: a not-present page shouldn't be cached */
update_mmu_cache(vma, address, entry);
spin_unlock(&mm->page_table_lock);
return 2; /* Major fault */
}
/*
* These routines also need to handle stuff like marking pages dirty
* and/or accessed for architectures that don't do it in hardware (most
* RISC architectures). The early dirtying is also good on the i386.
*
* There is also a hook called "update_mmu_cache()" that architectures
* with external mmu caches can use to update those (ie the Sparc or
* PowerPC hashed page tables that act as extended TLBs).
*
* Note the "page_table_lock". It is to protect against kswapd removing
* pages from under us. Note that kswapd only ever _removes_ pages, never
* adds them. As such, once we have noticed that the page is not present,
* we can drop the lock early.
*
* The adding of pages is protected by the MM semaphore (which we hold),
* so we don't need to worry about a page being suddenly been added into
* our VM.
*
* We enter with the pagetable spinlock held, we are supposed to
* release it when done.
*/
static inline int handle_pte_fault(struct mm_struct *mm,
struct vm_area_struct * vma, unsigned long address,
int write_access, pte_t * pte)
{
pte_t entry;
entry = *pte;
if (!pte_present(entry)) {
/*
* If it truly wasn't present, we know that kswapd
* and the PTE updates will not touch it later. So
* drop the lock.
*/
if (pte_none(entry))
return do_no_page(mm, vma, address, write_access, pte);
return do_swap_page(mm, vma, address, pte, entry, write_access);
}
if (write_access) {
if (!pte_write(entry))
return do_wp_page(mm, vma, address, pte, entry);
entry = pte_mkdirty(entry);
}
entry = pte_mkyoung(entry);
establish_pte(vma, address, pte, entry);
spin_unlock(&mm->page_table_lock);
return 1;
}
/*
* By the time we get here, we already hold the mm semaphore
*/
int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma,
unsigned long address, int write_access)
{
pgd_t *pgd;
pmd_t *pmd;
current->state = TASK_RUNNING;
pgd = pgd_offset(mm, address);
/*
* We need the page table lock to synchronize with kswapd
* and the SMP-safe atomic PTE updates.
*/
spin_lock(&mm->page_table_lock);
pmd = pmd_alloc(mm, pgd, address);
if (pmd) {
pte_t * pte = pte_alloc(mm, pmd, address);
if (pte)
return handle_pte_fault(mm, vma, address, write_access, pte);
}
spin_unlock(&mm->page_table_lock);
return -1;
}
/*
* Allocate page middle directory.
*
* We've already handled the fast-path in-line, and we own the
* page table lock.
*
* On a two-level page table, this ends up actually being entirely
* optimized away.
*/
pmd_t *__pmd_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
{
pmd_t *new;
/* "fast" allocation can happen without dropping the lock.. */
new = pmd_alloc_one_fast(mm, address);
if (!new) {
spin_unlock(&mm->page_table_lock);
new = pmd_alloc_one(mm, address);
spin_lock(&mm->page_table_lock);
if (!new)
return NULL;
/*
* Because we dropped the lock, we should re-check the
* entry, as somebody else could have populated it..
*/
if (!pgd_none(*pgd)) {
pmd_free(new);
goto out;
}
}
pgd_populate(mm, pgd, new);
out:
return pmd_offset(pgd, address);
}
/*
* Allocate the page table directory.
*
* We've already handled the fast-path in-line, and we own the
* page table lock.
*/
pte_t *pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address)
{
if (pmd_none(*pmd)) {
pte_t *new;
/* "fast" allocation can happen without dropping the lock.. */
new = pte_alloc_one_fast(mm, address);
if (!new) {
spin_unlock(&mm->page_table_lock);
new = pte_alloc_one(mm, address);
spin_lock(&mm->page_table_lock);
if (!new)
return NULL;
/*
* Because we dropped the lock, we should re-check the
* entry, as somebody else could have populated it..
*/
if (!pmd_none(*pmd)) {
pte_free(new);
goto out;
}
}
pmd_populate(mm, pmd, new);
}
out:
return pte_offset(pmd, address);
}
int make_pages_present(unsigned long addr, unsigned long end)
{
int ret, len, write;
struct vm_area_struct * vma;
vma = find_vma(current->mm, addr);
write = (vma->vm_flags & VM_WRITE) != 0;
if (addr >= end)
BUG();
if (end > vma->vm_end)
BUG();
len = (end+PAGE_SIZE-1)/PAGE_SIZE-addr/PAGE_SIZE;
ret = get_user_pages(current, current->mm, addr,
len, write, 0, NULL, NULL);
return ret == len ? 0 : -1;
}
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