// SPDX-License-Identifier: GPL-2.0-or-later
/* file-nommu.c: no-MMU version of ramfs
*
* Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
* Written by David Howells ([email protected])
*/
#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 <linux/slab.h>
#include <linux/uaccess.h>
#include "internal.h"
static int ramfs_nommu_setattr(struct mnt_idmap *, struct dentry *, struct iattr *);
static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
unsigned long addr,
unsigned long len,
unsigned long pgoff,
unsigned long flags);
static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma);
static unsigned ramfs_mmap_capabilities(struct file *file)
{
return NOMMU_MAP_DIRECT | NOMMU_MAP_COPY | NOMMU_MAP_READ |
NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
}
const struct file_operations ramfs_file_operations = {
.mmap_capabilities = ramfs_mmap_capabilities,
.mmap = ramfs_nommu_mmap,
.get_unmapped_area = ramfs_nommu_get_unmapped_area,
.read_iter = generic_file_read_iter,
.write_iter = generic_file_write_iter,
.fsync = noop_fsync,
.splice_read = filemap_splice_read,
.splice_write = iter_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;
struct page *pages;
unsigned order;
void *data;
int ret;
gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
/* make various checks */
order = get_order(newsize);
if (unlikely(order > MAX_PAGE_ORDER))
return -EFBIG;
ret = inode_newsize_ok(inode, newsize);
if (ret)
return ret;
i_size_write(inode, newsize);
/* allocate enough contiguous pages to be able to satisfy the
* request */
pages = alloc_pages(gfp, 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);
if (ret < 0)
goto add_error;
/* prevent the page from being discarded on memory pressure */
SetPageDirty(page);
SetPageUptodate(page);
unlock_page(page);
put_page(page);
}
return 0;
add_error:
while (loop < npages)
__free_page(pages + loop++);
return ret;
}
/*****************************************************************************/
/*
*
*/
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 = nommu_shrink_inode_mappings(inode, size, newsize);
if (ret < 0)
return ret;
}
truncate_setsize(inode, newsize);
return 0;
}
/*****************************************************************************/
/*
* handle a change of attributes
* - we're specifically interested in a change of size
*/
static int ramfs_nommu_setattr(struct mnt_idmap *idmap,
struct dentry *dentry, struct iattr *ia)
{
struct inode *inode = d_inode(dentry);
unsigned int old_ia_valid = ia->ia_valid;
int ret = 0;
/* POSIX UID/GID verification for setting inode attributes */
ret = setattr_prepare(&nop_mnt_idmap, dentry, ia);
if (ret)
return ret;
/* pick out size-changing events */
if (ia->ia_valid & ATTR_SIZE) {
loff_t size = inode->i_size;
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;
}
}
setattr_copy(&nop_mnt_idmap, 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
*/
static 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_folios, loop, ret, nr_pages, pfn;
struct inode *inode = file_inode(file);
struct folio_batch fbatch;
loff_t isize;
/* the mapping mustn't extend beyond the EOF */
lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
isize = i_size_read(inode);
ret = -ENOSYS;
maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (pgoff >= maxpages)
goto out;
if (maxpages - pgoff < lpages)
goto out;
/* gang-find the pages */
folio_batch_init(&fbatch);
nr_pages = 0;
repeat:
nr_folios = filemap_get_folios_contig(inode->i_mapping, &pgoff,
ULONG_MAX, &fbatch);
if (!nr_folios) {
ret = -ENOSYS;
return ret;
}
if (ret == -ENOSYS) {
ret = (unsigned long) folio_address(fbatch.folios[0]);
pfn = folio_pfn(fbatch.folios[0]);
}
/* check the pages for physical adjacency */
for (loop = 0; loop < nr_folios; loop++) {
if (pfn + nr_pages != folio_pfn(fbatch.folios[loop])) {
ret = -ENOSYS;
goto out_free; /* leave if not physical adjacent */
}
nr_pages += folio_nr_pages(fbatch.folios[loop]);
if (nr_pages >= lpages)
goto out_free; /* successfully found desired pages*/
}
if (nr_pages < lpages) {
folio_batch_release(&fbatch);
goto repeat; /* loop if pages are missing */
}
/* okay - all conditions fulfilled */
out_free:
folio_batch_release(&fbatch);
out:
return ret;
}
/*****************************************************************************/
/*
* set up a mapping for shared memory segments
*/
static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
{
if (!is_nommu_shared_mapping(vma->vm_flags))
return -ENOSYS;
file_accessed(file);
vma->vm_ops = &generic_file_vm_ops;
return 0;
}
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