/*
* linux/mm/filemap.c
*
* Copyright (C) 1994-1999 Linus Torvalds
*/
/*
* This file handles the generic file mmap semantics used by
* most "normal" filesystems (but you don't /have/ to use this:
* the NFS filesystem used to do this differently, for example)
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/aio.h>
#include <linux/kernel_stat.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/hash.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/security.h>
/*
* This is needed for the following functions:
* - try_to_release_page
* - block_invalidatepage
* - page_has_buffers
* - generic_osync_inode
*
* FIXME: remove all knowledge of the buffer layer from this file
*/
#include <linux/buffer_head.h>
#include <asm/uaccess.h>
#include <asm/mman.h>
/*
* Shared mappings implemented 30.11.1994. It's not fully working yet,
* though.
*
* Shared mappings now work. 15.8.1995 Bruno.
*
* finished 'unifying' the page and buffer cache and SMP-threaded the
* page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
*
* SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
*/
/*
* Lock ordering:
*
* ->i_shared_lock (vmtruncate)
* ->private_lock (__free_pte->__set_page_dirty_buffers)
* ->swap_list_lock
* ->swap_device_lock (exclusive_swap_page, others)
* ->mapping->page_lock
* ->inode_lock
* ->sb_lock (fs/fs-writeback.c)
* ->mapping->page_lock (__sync_single_inode)
* ->page_table_lock
* ->swap_device_lock (try_to_unmap_one)
* ->private_lock (try_to_unmap_one)
* ->page_lock (try_to_unmap_one)
*/
/*
* Remove a page from the page cache and free it. Caller has to make
* sure the page is locked and that nobody else uses it - or that usage
* is safe. The caller must hold a write_lock on the mapping's page_lock.
*/
void __remove_from_page_cache(struct page *page)
{
struct address_space *mapping = page->mapping;
BUG_ON(PageDirty(page) && !PageSwapCache(page));
radix_tree_delete(&mapping->page_tree, page->index);
list_del(&page->list);
page->mapping = NULL;
mapping->nrpages--;
dec_page_state(nr_pagecache);
}
void remove_from_page_cache(struct page *page)
{
struct address_space *mapping = page->mapping;
if (unlikely(!PageLocked(page)))
PAGE_BUG(page);
write_lock(&mapping->page_lock);
__remove_from_page_cache(page);
write_unlock(&mapping->page_lock);
}
static inline int sync_page(struct page *page)
{
struct address_space *mapping = page->mapping;
if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
return mapping->a_ops->sync_page(page);
return 0;
}
/**
* filemap_fdatawrite - start writeback against all of a mapping's dirty pages
* @mapping: address space structure to write
*
* This is a "data integrity" operation, as opposed to a regular memory
* cleansing writeback. The difference between these two operations is that
* if a dirty page/buffer is encountered, it must be waited upon, and not just
* skipped over.
*/
int filemap_fdatawrite(struct address_space *mapping)
{
int ret;
struct writeback_control wbc = {
.sync_mode = WB_SYNC_ALL,
.nr_to_write = mapping->nrpages * 2,
};
if (mapping->backing_dev_info->memory_backed)
return 0;
write_lock(&mapping->page_lock);
list_splice_init(&mapping->dirty_pages, &mapping->io_pages);
write_unlock(&mapping->page_lock);
ret = do_writepages(mapping, &wbc);
return ret;
}
/**
* filemap_fdatawait - walk the list of locked pages of the given address
* space and wait for all of them.
* @mapping: address space structure to wait for
*/
int filemap_fdatawait(struct address_space * mapping)
{
int ret = 0;
int progress;
restart:
progress = 0;
write_lock(&mapping->page_lock);
while (!list_empty(&mapping->locked_pages)) {
struct page *page;
page = list_entry(mapping->locked_pages.next,struct page,list);
list_del(&page->list);
if (PageDirty(page))
list_add(&page->list, &mapping->dirty_pages);
else
list_add(&page->list, &mapping->clean_pages);
if (!PageWriteback(page)) {
if (++progress > 32) {
if (need_resched()) {
write_unlock(&mapping->page_lock);
__cond_resched();
goto restart;
}
}
continue;
}
progress = 0;
page_cache_get(page);
write_unlock(&mapping->page_lock);
wait_on_page_writeback(page);
if (PageError(page))
ret = -EIO;
page_cache_release(page);
write_lock(&mapping->page_lock);
}
write_unlock(&mapping->page_lock);
return ret;
}
/*
* This adds a page to the page cache, starting out as locked, unreferenced,
* not uptodate and with no errors.
*
* This function is used for two things: adding newly allocated pagecache
* pages and for moving existing anon pages into swapcache.
*
* In the case of pagecache pages, the page is new, so we can just run
* SetPageLocked() against it. The other page state flags were set by
* rmqueue()
*
* In the case of swapcache, try_to_swap_out() has already locked the page, so
* SetPageLocked() is ugly-but-OK there too. The required page state has been
* set up by swap_out_add_to_swap_cache().
*
* This function does not add the page to the LRU. The caller must do that.
*/
int add_to_page_cache(struct page *page,
struct address_space *mapping, pgoff_t offset)
{
int error;
page_cache_get(page);
write_lock(&mapping->page_lock);
error = radix_tree_insert(&mapping->page_tree, offset, page);
if (!error) {
SetPageLocked(page);
___add_to_page_cache(page, mapping, offset);
} else {
page_cache_release(page);
}
write_unlock(&mapping->page_lock);
return error;
}
int add_to_page_cache_lru(struct page *page,
struct address_space *mapping, pgoff_t offset)
{
int ret = add_to_page_cache(page, mapping, offset);
if (ret == 0)
lru_cache_add(page);
return ret;
}
/*
* In order to wait for pages to become available there must be
* waitqueues associated with pages. By using a hash table of
* waitqueues where the bucket discipline is to maintain all
* waiters on the same queue and wake all when any of the pages
* become available, and for the woken contexts to check to be
* sure the appropriate page became available, this saves space
* at a cost of "thundering herd" phenomena during rare hash
* collisions.
*/
static wait_queue_head_t *page_waitqueue(struct page *page)
{
const struct zone *zone = page_zone(page);
return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
}
void wait_on_page_bit(struct page *page, int bit_nr)
{
wait_queue_head_t *waitqueue = page_waitqueue(page);
DEFINE_WAIT(wait);
do {
prepare_to_wait(waitqueue, &wait, TASK_UNINTERRUPTIBLE);
sync_page(page);
if (test_bit(bit_nr, &page->flags))
io_schedule();
} while (test_bit(bit_nr, &page->flags));
finish_wait(waitqueue, &wait);
}
EXPORT_SYMBOL(wait_on_page_bit);
/**
* unlock_page() - unlock a locked page
*
* @page: the page
*
* Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
* Also wakes sleepers in wait_on_page_writeback() because the wakeup
* mechananism between PageLocked pages and PageWriteback pages is shared.
* But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
*
* The first mb is necessary to safely close the critical section opened by the
* TestSetPageLocked(), the second mb is necessary to enforce ordering between
* the clear_bit and the read of the waitqueue (to avoid SMP races with a
* parallel wait_on_page_locked()).
*/
void unlock_page(struct page *page)
{
wait_queue_head_t *waitqueue = page_waitqueue(page);
smp_mb__before_clear_bit();
if (!TestClearPageLocked(page))
BUG();
smp_mb__after_clear_bit();
if (waitqueue_active(waitqueue))
wake_up_all(waitqueue);
}
/*
* End writeback against a page.
*/
void end_page_writeback(struct page *page)
{
wait_queue_head_t *waitqueue = page_waitqueue(page);
if (!TestClearPageReclaim(page) || rotate_reclaimable_page(page)) {
smp_mb__before_clear_bit();
if (!TestClearPageWriteback(page))
BUG();
smp_mb__after_clear_bit();
}
if (waitqueue_active(waitqueue))
wake_up_all(waitqueue);
}
EXPORT_SYMBOL(end_page_writeback);
/*
* Get a lock on the page, assuming we need to sleep to get it.
*
* Ugly: running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some
* random driver's requestfn sets TASK_RUNNING, we could busywait. However
* chances are that on the second loop, the block layer's plug list is empty,
* so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
*/
void __lock_page(struct page *page)
{
wait_queue_head_t *wqh = page_waitqueue(page);
DEFINE_WAIT(wait);
while (TestSetPageLocked(page)) {
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
sync_page(page);
if (PageLocked(page))
io_schedule();
}
finish_wait(wqh, &wait);
}
EXPORT_SYMBOL(__lock_page);
/*
* a rather lightweight function, finding and getting a reference to a
* hashed page atomically.
*/
struct page * find_get_page(struct address_space *mapping, unsigned long offset)
{
struct page *page;
/*
* We scan the hash list read-only. Addition to and removal from
* the hash-list needs a held write-lock.
*/
read_lock(&mapping->page_lock);
page = radix_tree_lookup(&mapping->page_tree, offset);
if (page)
page_cache_get(page);
read_unlock(&mapping->page_lock);
return page;
}
/*
* Same as above, but trylock it instead of incrementing the count.
*/
struct page *find_trylock_page(struct address_space *mapping, unsigned long offset)
{
struct page *page;
read_lock(&mapping->page_lock);
page = radix_tree_lookup(&mapping->page_tree, offset);
if (page && TestSetPageLocked(page))
page = NULL;
read_unlock(&mapping->page_lock);
return page;
}
/**
* find_lock_page - locate, pin and lock a pagecache page
*
* @mapping - the address_space to search
* @offset - the page index
*
* Locates the desired pagecache page, locks it, increments its reference
* count and returns its address.
*
* Returns zero if the page was not present. find_lock_page() may sleep.
*/
struct page *find_lock_page(struct address_space *mapping,
unsigned long offset)
{
struct page *page;
read_lock(&mapping->page_lock);
repeat:
page = radix_tree_lookup(&mapping->page_tree, offset);
if (page) {
page_cache_get(page);
if (TestSetPageLocked(page)) {
read_unlock(&mapping->page_lock);
lock_page(page);
read_lock(&mapping->page_lock);
/* Has the page been truncated while we slept? */
if (page->mapping != mapping || page->index != offset) {
unlock_page(page);
page_cache_release(page);
goto repeat;
}
}
}
read_unlock(&mapping->page_lock);
return page;
}
/**
* find_or_create_page - locate or add a pagecache page
*
* @mapping - the page's address_space
* @index - the page's index into the mapping
* @gfp_mask - page allocation mode
*
* Locates a page in the pagecache. If the page is not present, a new page
* is allocated using @gfp_mask and is added to the pagecache and to the VM's
* LRU list. The returned page is locked and has its reference count
* incremented.
*
* find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
* allocation!
*
* find_or_create_page() returns the desired page's address, or zero on
* memory exhaustion.
*/
struct page *find_or_create_page(struct address_space *mapping,
unsigned long index, unsigned int gfp_mask)
{
struct page *page, *cached_page = NULL;
int err;
repeat:
page = find_lock_page(mapping, index);
if (!page) {
if (!cached_page) {
cached_page = alloc_page(gfp_mask);
if (!cached_page)
return NULL;
}
err = add_to_page_cache_lru(cached_page, mapping, index);
if (!err) {
page = cached_page;
cached_page = NULL;
} else if (err == -EEXIST)
goto repeat;
}
if (cached_page)
page_cache_release(cached_page);
return page;
}
/**
* find_get_pages - gang pagecache lookup
* @mapping: The address_space to search
* @start: The starting page index
* @nr_pages: The maximum number of pages
* @pages: Where the resulting pages are placed
*
* find_get_pages() will search for and return a group of up to
* @nr_pages pages in the mapping. The pages are placed at @pages.
* find_get_pages() takes a reference against the returned pages.
*
* The search returns a group of mapping-contiguous pages with ascending
* indexes. There may be holes in the indices due to not-present pages.
*
* find_get_pages() returns the number of pages which were found.
*/
unsigned int find_get_pages(struct address_space *mapping, pgoff_t start,
unsigned int nr_pages, struct page **pages)
{
unsigned int i;
unsigned int ret;
read_lock(&mapping->page_lock);
ret = radix_tree_gang_lookup(&mapping->page_tree,
(void **)pages, start, nr_pages);
for (i = 0; i < ret; i++)
page_cache_get(pages[i]);
read_unlock(&mapping->page_lock);
return ret;
}
/*
* Same as grab_cache_page, but do not wait if the page is unavailable.
* This is intended for speculative data generators, where the data can
* be regenerated if the page couldn't be grabbed. This routine should
* be safe to call while holding the lock for another page.
*
* Clear __GFP_FS when allocating the page to avoid recursion into the fs
* and deadlock against the caller's locked page.
*/
struct page *
grab_cache_page_nowait(struct address_space *mapping, unsigned long index)
{
struct page *page = find_get_page(mapping, index);
if (page) {
if (!TestSetPageLocked(page))
return page;
page_cache_release(page);
return NULL;
}
page = alloc_pages(mapping->gfp_mask & ~__GFP_FS, 0);
if (page && add_to_page_cache_lru(page, mapping, index)) {
page_cache_release(page);
page = NULL;
}
return page;
}
/*
* This is a generic file read routine, and uses the
* inode->i_op->readpage() function for the actual low-level
* stuff.
*
* This is really ugly. But the goto's actually try to clarify some
* of the logic when it comes to error handling etc.
* - note the struct file * is only passed for the use of readpage
*/
void do_generic_mapping_read(struct address_space *mapping,
struct file_ra_state *ra,
struct file * filp,
loff_t *ppos,
read_descriptor_t * desc,
read_actor_t actor)
{
struct inode *inode = mapping->host;
unsigned long index, offset;
struct page *cached_page;
int error;
cached_page = NULL;
index = *ppos >> PAGE_CACHE_SHIFT;
offset = *ppos & ~PAGE_CACHE_MASK;
for (;;) {
struct page *page;
unsigned long end_index, nr, ret;
end_index = inode->i_size >> PAGE_CACHE_SHIFT;
if (index > end_index)
break;
nr = PAGE_CACHE_SIZE;
if (index == end_index) {
nr = inode->i_size & ~PAGE_CACHE_MASK;
if (nr <= offset)
break;
}
cond_resched();
page_cache_readahead(mapping, ra, filp, index);
nr = nr - offset;
/*
* Try to find the data in the page cache..
*/
find_page:
read_lock(&mapping->page_lock);
page = radix_tree_lookup(&mapping->page_tree, index);
if (!page) {
read_unlock(&mapping->page_lock);
handle_ra_miss(mapping,ra);
goto no_cached_page;
}
page_cache_get(page);
read_unlock(&mapping->page_lock);
if (!PageUptodate(page))
goto page_not_up_to_date;
page_ok:
/* If users can be writing to this page using arbitrary
* virtual addresses, take care about potential aliasing
* before reading the page on the kernel side.
*/
if (!list_empty(&mapping->i_mmap_shared))
flush_dcache_page(page);
/*
* Mark the page accessed if we read the beginning.
*/
if (!offset)
mark_page_accessed(page);
/*
* Ok, we have the page, and it's up-to-date, so
* now we can copy it to user space...
*
* The actor routine returns how many bytes were actually used..
* NOTE! This may not be the same as how much of a user buffer
* we filled up (we may be padding etc), so we can only update
* "pos" here (the actor routine has to update the user buffer
* pointers and the remaining count).
*/
ret = actor(desc, page, offset, nr);
offset += ret;
index += offset >> PAGE_CACHE_SHIFT;
offset &= ~PAGE_CACHE_MASK;
page_cache_release(page);
if (ret == nr && desc->count)
continue;
break;
page_not_up_to_date:
if (PageUptodate(page))
goto page_ok;
/* Get exclusive access to the page ... */
lock_page(page);
/* Did it get unhashed before we got the lock? */
if (!page->mapping) {
unlock_page(page);
page_cache_release(page);
continue;
}
/* Did somebody else fill it already? */
if (PageUptodate(page)) {
unlock_page(page);
goto page_ok;
}
readpage:
/* ... and start the actual read. The read will unlock the page. */
error = mapping->a_ops->readpage(filp, page);
if (!error) {
if (PageUptodate(page))
goto page_ok;
wait_on_page_locked(page);
if (PageUptodate(page))
goto page_ok;
error = -EIO;
}
/* UHHUH! A synchronous read error occurred. Report it */
desc->error = error;
page_cache_release(page);
break;
no_cached_page:
/*
* Ok, it wasn't cached, so we need to create a new
* page..
*/
if (!cached_page) {
cached_page = page_cache_alloc_cold(mapping);
if (!cached_page) {
desc->error = -ENOMEM;
break;
}
}
error = add_to_page_cache_lru(cached_page, mapping, index);
if (error) {
if (error == -EEXIST)
goto find_page;
desc->error = error;
break;
}
page = cached_page;
cached_page = NULL;
goto readpage;
}
*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
if (cached_page)
page_cache_release(cached_page);
UPDATE_ATIME(inode);
}
/*
* Fault a userspace page into pagetables. Return non-zero on a fault.
*
* FIXME: this assumes that two userspace pages are always sufficient. That's
* not true if PAGE_CACHE_SIZE > PAGE_SIZE.
*/
static inline int fault_in_pages_writeable(char *uaddr, int size)
{
int ret;
/*
* Writing zeroes into userspace here is OK, because we know that if
* the zero gets there, we'll be overwriting it.
*/
ret = __put_user(0, uaddr);
if (ret == 0) {
char *end = uaddr + size - 1;
/*
* If the page was already mapped, this will get a cache miss
* for sure, so try to avoid doing it.
*/
if (((unsigned long)uaddr & PAGE_MASK) !=
((unsigned long)end & PAGE_MASK))
ret = __put_user(0, end);
}
return ret;
}
static void fault_in_pages_readable(const char *uaddr, int size)
{
volatile char c;
int ret;
ret = __get_user(c, (char *)uaddr);
if (ret == 0) {
const char *end = uaddr + size - 1;
if (((unsigned long)uaddr & PAGE_MASK) !=
((unsigned long)end & PAGE_MASK))
__get_user(c, (char *)end);
}
}
int file_read_actor(read_descriptor_t *desc, struct page *page,
unsigned long offset, unsigned long size)
{
char *kaddr;
unsigned long left, count = desc->count;
if (size > count)
size = count;
/*
* Faults on the destination of a read are common, so do it before
* taking the kmap.
*/
if (!fault_in_pages_writeable(desc->buf, size)) {
kaddr = kmap_atomic(page, KM_USER0);
left = __copy_to_user(desc->buf, kaddr + offset, size);
kunmap_atomic(kaddr, KM_USER0);
if (left == 0)
goto success;
}
/* Do it the slow way */
kaddr = kmap(page);
left = __copy_to_user(desc->buf, kaddr + offset, size);
kunmap(page);
if (left) {
size -= left;
desc->error = -EFAULT;
}
success:
desc->count = count - size;
desc->written += size;
desc->buf += size;
return size;
}
/*
* This is the "read()" routine for all filesystems
* that can use the page cache directly.
*/
static ssize_t
__generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
unsigned long nr_segs, loff_t *ppos)
{
struct file *filp = iocb->ki_filp;
ssize_t retval;
unsigned long seg;
size_t count;
count = 0;
for (seg = 0; seg < nr_segs; seg++) {
const struct iovec *iv = &iov[seg];
/*
* If any segment has a negative length, or the cumulative
* length ever wraps negative then return -EINVAL.
*/
count += iv->iov_len;
if (unlikely((ssize_t)(count|iv->iov_len) < 0))
return -EINVAL;
if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
continue;
if (seg == 0)
return -EFAULT;
nr_segs = seg;
count -= iv->iov_len; /* This segment is no good */
break;
}
/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
if (filp->f_flags & O_DIRECT) {
loff_t pos = *ppos, size;
struct address_space *mapping;
struct inode *inode;
mapping = filp->f_dentry->d_inode->i_mapping;
inode = mapping->host;
retval = 0;
if (!count)
goto out; /* skip atime */
size = inode->i_size;
if (pos < size) {
if (pos + count > size) {
count = size - pos;
nr_segs = iov_shorten((struct iovec *)iov,
nr_segs, count);
}
retval = generic_file_direct_IO(READ, filp,
iov, pos, nr_segs);
if (retval > 0)
*ppos = pos + retval;
}
UPDATE_ATIME(filp->f_dentry->d_inode);
goto out;
}
retval = 0;
if (count) {
for (seg = 0; seg < nr_segs; seg++) {
read_descriptor_t desc;
desc.written = 0;
desc.buf = iov[seg].iov_base;
desc.count = iov[seg].iov_len;
if (desc.count == 0)
continue;
desc.error = 0;
do_generic_file_read(filp,ppos,&desc,file_read_actor);
retval += desc.written;
if (!retval) {
retval = desc.error;
break;
}
}
}
out:
return retval;
}
ssize_t
generic_file_aio_read(struct kiocb *iocb, char *buf, size_t count, loff_t pos)
{
struct iovec local_iov = { .iov_base = buf, .iov_len = count };
BUG_ON(iocb->ki_pos != pos);
return __generic_file_aio_read(iocb, &local_iov, 1, &iocb->ki_pos);
}
EXPORT_SYMBOL(generic_file_aio_read);
ssize_t
generic_file_read(struct file *filp, char *buf, size_t count, loff_t *ppos)
{
struct iovec local_iov = { .iov_base = buf, .iov_len = count };
struct kiocb kiocb;
ssize_t ret;
init_sync_kiocb(&kiocb, filp);
ret = __generic_file_aio_read(&kiocb, &local_iov, 1, ppos);
if (-EIOCBQUEUED == ret)
ret = wait_on_sync_kiocb(&kiocb);
return ret;
}
int file_send_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size)
{
ssize_t written;
unsigned long count = desc->count;
struct file *file = (struct file *) desc->buf;
if (size > count)
size = count;
written = file->f_op->sendpage(file, page, offset,
size, &file->f_pos, size<count);
if (written < 0) {
desc->error = written;
written = 0;
}
desc->count = count - written;
desc->written += written;
return written;
}
ssize_t generic_file_sendfile(struct file *in_file, loff_t *ppos,
size_t count, read_actor_t actor, void *target)
{
read_descriptor_t desc;
if (!count)
return 0;
desc.written = 0;
desc.count = count;
desc.buf = target;
desc.error = 0;
do_generic_file_read(in_file, ppos, &desc, actor);
if (desc.written)
return desc.written;
return desc.error;
}
static ssize_t
do_readahead(struct address_space *mapping, struct file *filp,
unsigned long index, unsigned long nr)
{
if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
return -EINVAL;
do_page_cache_readahead(mapping, filp, index, max_sane_readahead(nr));
return 0;
}
asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count)
{
ssize_t ret;
struct file *file;
ret = -EBADF;
file = fget(fd);
if (file) {
if (file->f_mode & FMODE_READ) {
struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
unsigned long start = offset >> PAGE_CACHE_SHIFT;
unsigned long end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
unsigned long len = end - start + 1;
ret = do_readahead(mapping, file, start, len);
}
fput(file);
}
return ret;
}
#ifdef CONFIG_MMU
/*
* This adds the requested page to the page cache if it isn't already there,
* and schedules an I/O to read in its contents from disk.
*/
static int FASTCALL(page_cache_read(struct file * file, unsigned long offset));
static int page_cache_read(struct file * file, unsigned long offset)
{
struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
struct page *page;
int error;
page = page_cache_alloc_cold(mapping);
if (!page)
return -ENOMEM;
error = add_to_page_cache_lru(page, mapping, offset);
if (!error) {
error = mapping->a_ops->readpage(file, page);
page_cache_release(page);
return error;
}
/*
* We arrive here in the unlikely event that someone
* raced with us and added our page to the cache first
* or we are out of memory for radix-tree nodes.
*/
page_cache_release(page);
return error == -EEXIST ? 0 : error;
}
/*
* filemap_nopage() is invoked via the vma operations vector for a
* mapped memory region to read in file data during a page fault.
*
* The goto's are kind of ugly, but this streamlines the normal case of having
* it in the page cache, and handles the special cases reasonably without
* having a lot of duplicated code.
*/
struct page * filemap_nopage(struct vm_area_struct * area, unsigned long address, int unused)
{
int error;
struct file *file = area->vm_file;
struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
struct file_ra_state *ra = &file->f_ra;
struct inode *inode = mapping->host;
struct page *page;
unsigned long size, pgoff, endoff;
int did_readahead;
pgoff = ((address - area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff;
endoff = ((area->vm_end - area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff;
retry_all:
/*
* An external ptracer can access pages that normally aren't
* accessible..
*/
size = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if ((pgoff >= size) && (area->vm_mm == current->mm))
return NULL;
/*
* The "size" of the file, as far as mmap is concerned, isn't bigger
* than the mapping
*/
if (size > endoff)
size = endoff;
did_readahead = 0;
/*
* The readahead code wants to be told about each and every page
* so it can build and shrink its windows appropriately
*/
if (VM_SequentialReadHint(area)) {
did_readahead = 1;
page_cache_readahead(mapping, ra, file, pgoff);
}
/*
* If the offset is outside the mapping size we're off the end
* of a privately mapped file, so we need to map a zero page.
*/
if ((pgoff < size) && !VM_RandomReadHint(area)) {
did_readahead = 1;
page_cache_readaround(mapping, ra, file, pgoff);
}
/*
* Do we have something in the page cache already?
*/
retry_find:
page = find_get_page(mapping, pgoff);
if (!page) {
if (did_readahead) {
handle_ra_miss(mapping,ra);
did_readahead = 0;
}
goto no_cached_page;
}
/*
* Ok, found a page in the page cache, now we need to check
* that it's up-to-date.
*/
if (!PageUptodate(page))
goto page_not_uptodate;
success:
/*
* Found the page and have a reference on it, need to check sharing
* and possibly copy it over to another page..
*/
mark_page_accessed(page);
flush_page_to_ram(page);
return page;
no_cached_page:
/*
* We're only likely to ever get here if MADV_RANDOM is in
* effect.
*/
error = page_cache_read(file, pgoff);
/*
* The page we want has now been added to the page cache.
* In the unlikely event that someone removed it in the
* meantime, we'll just come back here and read it again.
*/
if (error >= 0)
goto retry_find;
/*
* An error return from page_cache_read can result if the
* system is low on memory, or a problem occurs while trying
* to schedule I/O.
*/
if (error == -ENOMEM)
return NOPAGE_OOM;
return NULL;
page_not_uptodate:
inc_page_state(pgmajfault);
lock_page(page);
/* Did it get unhashed while we waited for it? */
if (!page->mapping) {
unlock_page(page);
page_cache_release(page);
goto retry_all;
}
/* Did somebody else get it up-to-date? */
if (PageUptodate(page)) {
unlock_page(page);
goto success;
}
if (!mapping->a_ops->readpage(file, page)) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
}
/*
* Umm, take care of errors if the page isn't up-to-date.
* Try to re-read it _once_. We do this synchronously,
* because there really aren't any performance issues here
* and we need to check for errors.
*/
lock_page(page);
/* Somebody truncated the page on us? */
if (!page->mapping) {
unlock_page(page);
page_cache_release(page);
goto retry_all;
}
/* Somebody else successfully read it in? */
if (PageUptodate(page)) {
unlock_page(page);
goto success;
}
ClearPageError(page);
if (!mapping->a_ops->readpage(file, page)) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
}
/*
* Things didn't work out. Return zero to tell the
* mm layer so, possibly freeing the page cache page first.
*/
page_cache_release(page);
return NULL;
}
static struct page * filemap_getpage(struct file *file, unsigned long pgoff,
int nonblock)
{
struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
struct page *page;
int error;
/*
* Do we have something in the page cache already?
*/
retry_find:
page = find_get_page(mapping, pgoff);
if (!page) {
if (nonblock)
return NULL;
goto no_cached_page;
}
/*
* Ok, found a page in the page cache, now we need to check
* that it's up-to-date.
*/
if (!PageUptodate(page))
goto page_not_uptodate;
success:
/*
* Found the page and have a reference on it, need to check sharing
* and possibly copy it over to another page..
*/
mark_page_accessed(page);
flush_page_to_ram(page);
return page;
no_cached_page:
error = page_cache_read(file, pgoff);
/*
* The page we want has now been added to the page cache.
* In the unlikely event that someone removed it in the
* meantime, we'll just come back here and read it again.
*/
if (error >= 0)
goto retry_find;
/*
* An error return from page_cache_read can result if the
* system is low on memory, or a problem occurs while trying
* to schedule I/O.
*/
return NULL;
page_not_uptodate:
lock_page(page);
/* Did it get unhashed while we waited for it? */
if (!page->mapping) {
unlock_page(page);
goto err;
}
/* Did somebody else get it up-to-date? */
if (PageUptodate(page)) {
unlock_page(page);
goto success;
}
if (!mapping->a_ops->readpage(file, page)) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
}
/*
* Umm, take care of errors if the page isn't up-to-date.
* Try to re-read it _once_. We do this synchronously,
* because there really aren't any performance issues here
* and we need to check for errors.
*/
lock_page(page);
/* Somebody truncated the page on us? */
if (!page->mapping) {
unlock_page(page);
goto err;
}
/* Somebody else successfully read it in? */
if (PageUptodate(page)) {
unlock_page(page);
goto success;
}
ClearPageError(page);
if (!mapping->a_ops->readpage(file, page)) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
}
/*
* Things didn't work out. Return zero to tell the
* mm layer so, possibly freeing the page cache page first.
*/
err:
page_cache_release(page);
return NULL;
}
static int filemap_populate(struct vm_area_struct *vma,
unsigned long addr,
unsigned long len,
unsigned long prot,
unsigned long pgoff,
int nonblock)
{
struct file *file = vma->vm_file;
struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
struct inode *inode = mapping->host;
unsigned long size;
struct mm_struct *mm = vma->vm_mm;
struct page *page;
int err;
repeat:
size = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (pgoff + (len >> PAGE_CACHE_SHIFT) > size)
return -EINVAL;
page = filemap_getpage(file, pgoff, nonblock);
if (!page && !nonblock)
return -ENOMEM;
if (page) {
err = install_page(mm, vma, addr, page, prot);
if (err) {
page_cache_release(page);
return err;
}
}
len -= PAGE_SIZE;
addr += PAGE_SIZE;
pgoff++;
if (len)
goto repeat;
return 0;
}
static struct vm_operations_struct generic_file_vm_ops = {
.nopage = filemap_nopage,
.populate = filemap_populate,
};
/* This is used for a general mmap of a disk file */
int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
{
struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
struct inode *inode = mapping->host;
if (!mapping->a_ops->readpage)
return -ENOEXEC;
UPDATE_ATIME(inode);
vma->vm_ops = &generic_file_vm_ops;
return 0;
}
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
{
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_WRITE))
return -EINVAL;
vma->vm_flags &= ~VM_MAYWRITE;
return generic_file_mmap(file, vma);
}
#else
int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
{
return -ENOSYS;
}
#endif /* CONFIG_MMU */
static inline struct page *__read_cache_page(struct address_space *mapping,
unsigned long index,
int (*filler)(void *,struct page*),
void *data)
{
struct page *page, *cached_page = NULL;
int err;
repeat:
page = find_get_page(mapping, index);
if (!page) {
if (!cached_page) {
cached_page = page_cache_alloc_cold(mapping);
if (!cached_page)
return ERR_PTR(-ENOMEM);
}
err = add_to_page_cache_lru(cached_page, mapping, index);
if (err == -EEXIST)
goto repeat;
if (err < 0) {
/* Presumably ENOMEM for radix tree node */
page_cache_release(cached_page);
return ERR_PTR(err);
}
page = cached_page;
cached_page = NULL;
err = filler(data, page);
if (err < 0) {
page_cache_release(page);
page = ERR_PTR(err);
}
}
if (cached_page)
page_cache_release(cached_page);
return page;
}
/*
* Read into the page cache. If a page already exists,
* and PageUptodate() is not set, try to fill the page.
*/
struct page *read_cache_page(struct address_space *mapping,
unsigned long index,
int (*filler)(void *,struct page*),
void *data)
{
struct page *page;
int err;
retry:
page = __read_cache_page(mapping, index, filler, data);
if (IS_ERR(page))
goto out;
mark_page_accessed(page);
if (PageUptodate(page))
goto out;
lock_page(page);
if (!page->mapping) {
unlock_page(page);
page_cache_release(page);
goto retry;
}
if (PageUptodate(page)) {
unlock_page(page);
goto out;
}
err = filler(data, page);
if (err < 0) {
page_cache_release(page);
page = ERR_PTR(err);
}
out:
return page;
}
/*
* If the page was newly created, increment its refcount and add it to the
* caller's lru-buffering pagevec. This function is specifically for
* generic_file_write().
*/
static inline struct page *
__grab_cache_page(struct address_space *mapping, unsigned long index,
struct page **cached_page, struct pagevec *lru_pvec)
{
int err;
struct page *page;
repeat:
page = find_lock_page(mapping, index);
if (!page) {
if (!*cached_page) {
*cached_page = page_cache_alloc(mapping);
if (!*cached_page)
return NULL;
}
err = add_to_page_cache(*cached_page, mapping, index);
if (err == -EEXIST)
goto repeat;
if (err == 0) {
page = *cached_page;
page_cache_get(page);
if (!pagevec_add(lru_pvec, page))
__pagevec_lru_add(lru_pvec);
*cached_page = NULL;
}
}
return page;
}
void remove_suid(struct dentry *dentry)
{
struct iattr newattrs;
struct inode *inode = dentry->d_inode;
unsigned int mode = inode->i_mode & (S_ISUID|S_ISGID|S_IXGRP);
if (!(mode & S_IXGRP))
mode &= S_ISUID;
/* was any of the uid bits set? */
if (mode && !capable(CAP_FSETID)) {
newattrs.ia_valid = ATTR_KILL_SUID | ATTR_KILL_SGID;
notify_change(dentry, &newattrs);
}
}
static inline int
filemap_copy_from_user(struct page *page, unsigned long offset,
const char *buf, unsigned bytes)
{
char *kaddr;
int left;
kaddr = kmap_atomic(page, KM_USER0);
left = __copy_from_user(kaddr + offset, buf, bytes);
kunmap_atomic(kaddr, KM_USER0);
if (left != 0) {
/* Do it the slow way */
kaddr = kmap(page);
left = __copy_from_user(kaddr + offset, buf, bytes);
kunmap(page);
}
return left;
}
static int
__filemap_copy_from_user_iovec(char *vaddr,
const struct iovec *iov, size_t base, size_t bytes)
{
int left = 0;
while (bytes) {
char *buf = iov->iov_base + base;
int copy = min(bytes, iov->iov_len - base);
base = 0;
if ((left = __copy_from_user(vaddr, buf, copy)))
break;
bytes -= copy;
vaddr += copy;
iov++;
}
return left;
}
static inline int
filemap_copy_from_user_iovec(struct page *page, unsigned long offset,
const struct iovec *iov, size_t base, size_t bytes)
{
char *kaddr;
int left;
kaddr = kmap_atomic(page, KM_USER0);
left = __filemap_copy_from_user_iovec(kaddr + offset, iov, base, bytes);
kunmap_atomic(kaddr, KM_USER0);
if (left != 0) {
kaddr = kmap(page);
left = __filemap_copy_from_user_iovec(kaddr + offset, iov, base, bytes);
kunmap(page);
}
return left;
}
static inline void
filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
{
const struct iovec *iov = *iovp;
size_t base = *basep;
while (bytes) {
int copy = min(bytes, iov->iov_len - base);
bytes -= copy;
base += copy;
if (iov->iov_len == base) {
iov++;
base = 0;
}
}
*iovp = iov;
*basep = base;
}
/*
* Write to a file through the page cache.
*
* We put everything into the page cache prior to writing it. This is not a
* problem when writing full pages. With partial pages, however, we first have
* to read the data into the cache, then dirty the page, and finally schedule
* it for writing by marking it dirty.
* okir@monad.swb.de
*/
ssize_t
generic_file_write_nolock(struct file *file, const struct iovec *iov,
unsigned long nr_segs, loff_t *ppos)
{
struct address_space * mapping = file->f_dentry->d_inode->i_mapping;
struct address_space_operations *a_ops = mapping->a_ops;
size_t ocount; /* original count */
size_t count; /* after file limit checks */
struct inode *inode = mapping->host;
unsigned long limit = current->rlim[RLIMIT_FSIZE].rlim_cur;
const int isblk = S_ISBLK(inode->i_mode);
long status = 0;
loff_t pos;
struct page *page;
struct page *cached_page = NULL;
ssize_t written;
int err;
size_t bytes;
struct pagevec lru_pvec;
const struct iovec *cur_iov = iov; /* current iovec */
size_t iov_base = 0; /* offset in the current iovec */
unsigned long seg;
char *buf;
ocount = 0;
for (seg = 0; seg < nr_segs; seg++) {
const struct iovec *iv = &iov[seg];
/*
* If any segment has a negative length, or the cumulative
* length ever wraps negative then return -EINVAL.
*/
ocount += iv->iov_len;
if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
return -EINVAL;
if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
continue;
if (seg == 0)
return -EFAULT;
nr_segs = seg;
ocount -= iv->iov_len; /* This segment is no good */
break;
}
count = ocount;
pos = *ppos;
if (unlikely(pos < 0))
return -EINVAL;
/* We can write back this queue in page reclaim */
current->backing_dev_info = mapping->backing_dev_info;
pagevec_init(&lru_pvec, 0);
if (unlikely(file->f_error)) {
err = file->f_error;
file->f_error = 0;
goto out;
}
written = 0;
if (!isblk) {
/* FIXME: this is for backwards compatibility with 2.4 */
if (file->f_flags & O_APPEND)
pos = inode->i_size;
if (limit != RLIM_INFINITY) {
if (pos >= limit) {
send_sig(SIGXFSZ, current, 0);
err = -EFBIG;
goto out;
}
if (pos > 0xFFFFFFFFULL || count > limit - (u32)pos) {
/* send_sig(SIGXFSZ, current, 0); */
count = limit - (u32)pos;
}
}
}
/*
* LFS rule
*/
if (unlikely(pos + count > MAX_NON_LFS &&
!(file->f_flags & O_LARGEFILE))) {
if (pos >= MAX_NON_LFS) {
send_sig(SIGXFSZ, current, 0);
err = -EFBIG;
goto out;
}
if (count > MAX_NON_LFS - (u32)pos) {
/* send_sig(SIGXFSZ, current, 0); */
count = MAX_NON_LFS - (u32)pos;
}
}
/*
* Are we about to exceed the fs block limit ?
*
* If we have written data it becomes a short write. If we have
* exceeded without writing data we send a signal and return EFBIG.
* Linus frestrict idea will clean these up nicely..
*/
if (likely(!isblk)) {
if (unlikely(pos >= inode->i_sb->s_maxbytes)) {
if (count || pos > inode->i_sb->s_maxbytes) {
send_sig(SIGXFSZ, current, 0);
err = -EFBIG;
goto out;
}
/* zero-length writes at ->s_maxbytes are OK */
}
if (unlikely(pos + count > inode->i_sb->s_maxbytes))
count = inode->i_sb->s_maxbytes - pos;
} else {
if (bdev_read_only(inode->i_bdev)) {
err = -EPERM;
goto out;
}
if (pos >= inode->i_size) {
if (count || pos > inode->i_size) {
err = -ENOSPC;
goto out;
}
}
if (pos + count > inode->i_size)
count = inode->i_size - pos;
}
err = 0;
if (count == 0)
goto out;
remove_suid(file->f_dentry);
inode_update_time(inode, 1);
/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
if (unlikely(file->f_flags & O_DIRECT)) {
if (count != ocount)
nr_segs = iov_shorten((struct iovec *)iov,
nr_segs, count);
written = generic_file_direct_IO(WRITE, file,
iov, pos, nr_segs);
if (written > 0) {
loff_t end = pos + written;
if (end > inode->i_size && !isblk) {
inode->i_size = end;
mark_inode_dirty(inode);
}
*ppos = end;
}
/*
* Sync the fs metadata but not the minor inode changes and
* of course not the data as we did direct DMA for the IO.
*/
if (written >= 0 && file->f_flags & O_SYNC)
status = generic_osync_inode(inode, OSYNC_METADATA);
goto out_status;
}
buf = iov->iov_base;
do {
unsigned long index;
unsigned long offset;
long page_fault;
offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
index = pos >> PAGE_CACHE_SHIFT;
bytes = PAGE_CACHE_SIZE - offset;
if (bytes > count)
bytes = count;
/*
* Bring in the user page that we will copy from _first_.
* Otherwise there's a nasty deadlock on copying from the
* same page as we're writing to, without it being marked
* up-to-date.
*/
fault_in_pages_readable(buf, bytes);
page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec);
if (!page) {
status = -ENOMEM;
break;
}
status = a_ops->prepare_write(file, page, offset, offset+bytes);
if (unlikely(status)) {
/*
* prepare_write() may have instantiated a few blocks
* outside i_size. Trim these off again.
*/
unlock_page(page);
page_cache_release(page);
if (pos + bytes > inode->i_size)
vmtruncate(inode, inode->i_size);
break;
}
if (likely(nr_segs == 1))
page_fault = filemap_copy_from_user(page, offset,
buf, bytes);
else
page_fault = filemap_copy_from_user_iovec(page, offset,
cur_iov, iov_base, bytes);
flush_dcache_page(page);
status = a_ops->commit_write(file, page, offset, offset+bytes);
if (unlikely(page_fault)) {
status = -EFAULT;
} else {
if (!status)
status = bytes;
if (status >= 0) {
written += status;
count -= status;
pos += status;
buf += status;
if (unlikely(nr_segs > 1))
filemap_set_next_iovec(&cur_iov,
&iov_base, status);
}
}
if (!PageReferenced(page))
SetPageReferenced(page);
unlock_page(page);
page_cache_release(page);
if (status < 0)
break;
balance_dirty_pages_ratelimited(mapping);
cond_resched();
} while (count);
*ppos = pos;
if (cached_page)
page_cache_release(cached_page);
/*
* For now, when the user asks for O_SYNC, we'll actually give O_DSYNC
*/
if (status >= 0) {
if ((file->f_flags & O_SYNC) || IS_SYNC(inode))
status = generic_osync_inode(inode,
OSYNC_METADATA|OSYNC_DATA);
}
out_status:
err = written ? written : status;
out:
pagevec_lru_add(&lru_pvec);
current->backing_dev_info = 0;
return err;
}
ssize_t generic_file_aio_write(struct kiocb *iocb, const char *buf,
size_t count, loff_t pos)
{
return generic_file_write(iocb->ki_filp, buf, count, &iocb->ki_pos);
}
EXPORT_SYMBOL(generic_file_aio_write);
ssize_t generic_file_write(struct file *file, const char *buf,
size_t count, loff_t *ppos)
{
struct inode *inode = file->f_dentry->d_inode->i_mapping->host;
int err;
struct iovec local_iov = { .iov_base = (void *)buf, .iov_len = count };
down(&inode->i_sem);
err = generic_file_write_nolock(file, &local_iov, 1, ppos);
up(&inode->i_sem);
return err;
}
ssize_t generic_file_readv(struct file *filp, const struct iovec *iov,
unsigned long nr_segs, loff_t *ppos)
{
struct kiocb kiocb;
ssize_t ret;
init_sync_kiocb(&kiocb, filp);
ret = __generic_file_aio_read(&kiocb, iov, nr_segs, ppos);
if (-EIOCBQUEUED == ret)
ret = wait_on_sync_kiocb(&kiocb);
return ret;
}
ssize_t generic_file_writev(struct file *file, const struct iovec *iov,
unsigned long nr_segs, loff_t * ppos)
{
struct inode *inode = file->f_dentry->d_inode;
ssize_t ret;
down(&inode->i_sem);
ret = generic_file_write_nolock(file, iov, nr_segs, ppos);
up(&inode->i_sem);
return ret;
}