fs/ramfs/file-nommu.c - maze/linux - Git at Google

 /* 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;
 	struct page *pages;
 	unsigned order;
 	void *data;
 	int ret;

 	/* make various checks */
 	order = get_order(newsize);
 	if (unlikely(order >= MAX_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(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;

 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;

 	down_write(&nommu_region_sem);

 	/* 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) {
 			up_write(&nommu_region_sem);
 			return -ETXTBSY; /* not quite true, but near enough */
 		}
 	}

 	up_write(&nommu_region_sem);
 	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;
 }
	/* 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;
	struct page *pages;
	unsigned order;
	void *data;
	int ret;

	/* make various checks */
	order = get_order(newsize);
	if (unlikely(order >= MAX_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(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;

	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;

	down_write(&nommu_region_sem);

	/* 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) {
	up_write(&nommu_region_sem);
	return -ETXTBSY; /* not quite true, but near enough */
	}
	}

	up_write(&nommu_region_sem);
	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;
	}