/* file-nommu.c: no-MMU version of ramfs
*
* Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/ramfs.h>
#include <linux/pagevec.h>
#include <linux/mman.h>
#include <linux/sched.h>
#include <asm/uaccess.h>
#include "internal.h"
static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
const struct address_space_operations ramfs_aops = {
.readpage = simple_readpage,
.write_begin = simple_write_begin,
.write_end = simple_write_end,
.set_page_dirty = __set_page_dirty_no_writeback,
};
const struct file_operations ramfs_file_operations = {
.mmap = ramfs_nommu_mmap,
.get_unmapped_area = ramfs_nommu_get_unmapped_area,
.read = do_sync_read,
.aio_read = generic_file_aio_read,
.write = do_sync_write,
.aio_write = generic_file_aio_write,
.fsync = simple_sync_file,
.splice_read = generic_file_splice_read,
.splice_write = generic_file_splice_write,
.llseek = generic_file_llseek,
};
const struct inode_operations ramfs_file_inode_operations = {
.setattr = ramfs_nommu_setattr,
.getattr = simple_getattr,
};
/*****************************************************************************/
/*
* add a contiguous set of pages into a ramfs inode when it's truncated from
* size 0 on the assumption that it's going to be used for an mmap of shared
* memory
*/
int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
{
unsigned long npages, xpages, loop, limit;
struct page *pages;
unsigned order;
void *data;
int ret;
/* make various checks */
order = get_order(newsize);
if (unlikely(order >= MAX_ORDER))
goto too_big;
limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
if (limit != RLIM_INFINITY && newsize > limit)
goto fsize_exceeded;
if (newsize > inode->i_sb->s_maxbytes)
goto too_big;
i_size_write(inode, newsize);
/* allocate enough contiguous pages to be able to satisfy the
* request */
pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
if (!pages)
return -ENOMEM;
/* split the high-order page into an array of single pages */
xpages = 1UL << order;
npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
split_page(pages, order);
/* trim off any pages we don't actually require */
for (loop = npages; loop < xpages; loop++)
__free_page(pages + loop);
/* clear the memory we allocated */
newsize = PAGE_SIZE * npages;
data = page_address(pages);
memset(data, 0, newsize);
/* attach all the pages to the inode's address space */
for (loop = 0; loop < npages; loop++) {
struct page *page = pages + loop;
ret = add_to_page_cache_lru(page, inode->i_mapping, loop,
GFP_KERNEL);
if (ret < 0)
goto add_error;
/* prevent the page from being discarded on memory pressure */
SetPageDirty(page);
unlock_page(page);
}
return 0;
fsize_exceeded:
send_sig(SIGXFSZ, current, 0);
too_big:
return -EFBIG;
add_error:
while (loop < npages)
__free_page(pages + loop++);
return ret;
}
/*****************************************************************************/
/*
* check that file shrinkage doesn't leave any VMAs dangling in midair
*/
static int ramfs_nommu_check_mappings(struct inode *inode,
size_t newsize, size_t size)
{
struct vm_area_struct *vma;
struct prio_tree_iter iter;
/* search for VMAs that fall within the dead zone */
vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
newsize >> PAGE_SHIFT,
(size + PAGE_SIZE - 1) >> PAGE_SHIFT
) {
/* found one - only interested if it's shared out of the page
* cache */
if (vma->vm_flags & VM_SHARED)
return -ETXTBSY; /* not quite true, but near enough */
}
return 0;
}
/*****************************************************************************/
/*
*
*/
static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
{
int ret;
/* assume a truncate from zero size is going to be for the purposes of
* shared mmap */
if (size == 0) {
if (unlikely(newsize >> 32))
return -EFBIG;
return ramfs_nommu_expand_for_mapping(inode, newsize);
}
/* check that a decrease in size doesn't cut off any shared mappings */
if (newsize < size) {
ret = ramfs_nommu_check_mappings(inode, newsize, size);
if (ret < 0)
return ret;
}
ret = vmtruncate(inode, newsize);
return ret;
}
/*****************************************************************************/
/*
* handle a change of attributes
* - we're specifically interested in a change of size
*/
static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
{
struct inode *inode = dentry->d_inode;
unsigned int old_ia_valid = ia->ia_valid;
int ret = 0;
/* POSIX UID/GID verification for setting inode attributes */
ret = inode_change_ok(inode, ia);
if (ret)
return ret;
/* pick out size-changing events */
if (ia->ia_valid & ATTR_SIZE) {
loff_t size = i_size_read(inode);
if (ia->ia_size != size) {
ret = ramfs_nommu_resize(inode, ia->ia_size, size);
if (ret < 0 || ia->ia_valid == ATTR_SIZE)
goto out;
} else {
/* we skipped the truncate but must still update
* timestamps
*/
ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
}
}
ret = inode_setattr(inode, ia);
out:
ia->ia_valid = old_ia_valid;
return ret;
}
/*****************************************************************************/
/*
* try to determine where a shared mapping can be made
* - we require that:
* - the pages to be mapped must exist
* - the pages be physically contiguous in sequence
*/
unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags)
{
unsigned long maxpages, lpages, nr, loop, ret;
struct inode *inode = file->f_path.dentry->d_inode;
struct page **pages = NULL, **ptr, *page;
loff_t isize;
if (!(flags & MAP_SHARED))
return addr;
/* the mapping mustn't extend beyond the EOF */
lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
isize = i_size_read(inode);
ret = -EINVAL;
maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (pgoff >= maxpages)
goto out;
if (maxpages - pgoff < lpages)
goto out;
/* gang-find the pages */
ret = -ENOMEM;
pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
if (!pages)
goto out_free;
nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
if (nr != lpages)
goto out_free_pages; /* leave if some pages were missing */
/* check the pages for physical adjacency */
ptr = pages;
page = *ptr++;
page++;
for (loop = lpages; loop > 1; loop--)
if (*ptr++ != page++)
goto out_free_pages;
/* okay - all conditions fulfilled */
ret = (unsigned long) page_address(pages[0]);
out_free_pages:
ptr = pages;
for (loop = nr; loop > 0; loop--)
put_page(*ptr++);
out_free:
kfree(pages);
out:
return ret;
}
/*****************************************************************************/
/*
* set up a mapping for shared memory segments
*/
int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
{
if (!(vma->vm_flags & VM_SHARED))
return -ENOSYS;
file_accessed(file);
vma->vm_ops = &generic_file_vm_ops;
return 0;
}
