1 files changed, 292 insertions, 0 deletions
diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
new file mode 100644
index 0000000..3f810ac
--- /dev/null
+++ b/fs/ramfs/file-nommu.c
@@ -0,0 +1,292 @@
+/* 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/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/smp_lock.h>
+#include <linux/backing-dev.h>
+#include <linux/ramfs.h>
+#include <linux/quotaops.h>
+#include <linux/pagevec.h>
+#include <linux/mman.h>
+
+#include <asm/uaccess.h>
+#include "internal.h"
+
+static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
+
+struct address_space_operations ramfs_aops = {
+	.readpage		= simple_readpage,
+	.prepare_write		= simple_prepare_write,
+	.commit_write		= simple_commit_write
+};
+
+struct file_operations ramfs_file_operations = {
+	.mmap			= ramfs_nommu_mmap,
+	.get_unmapped_area	= ramfs_nommu_get_unmapped_area,
+	.read			= generic_file_read,
+	.write			= generic_file_write,
+	.fsync			= simple_sync_file,
+	.sendfile		= generic_file_sendfile,
+	.llseek			= generic_file_llseek,
+};
+
+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
+ */
+static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
+{
+	struct pagevec lru_pvec;
+	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;
+
+	for (loop = 0; loop < npages; loop++)
+		set_page_count(pages + loop, 1);
+
+	/* 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 */
+	pagevec_init(&lru_pvec, 0);
+	for (loop = 0; loop < npages; loop++) {
+		struct page *page = pages + loop;
+
+		ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL);
+		if (ret < 0)
+			goto add_error;
+
+		if (!pagevec_add(&lru_pvec, page))
+			__pagevec_lru_add(&lru_pvec);
+
+		unlock_page(page);
+	}
+
+	pagevec_lru_add(&lru_pvec);
+	return 0;
+
+ fsize_exceeded:
+	send_sig(SIGXFSZ, current, 0);
+ too_big:
+	return -EFBIG;
+
+ add_error:
+	page_cache_release(pages + loop);
+	for (loop++; loop < npages; loop++)
+		__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, size);
+
+	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;
+
+	/* by providing our own setattr() method, we skip this quotaism */
+	if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) ||
+	    (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid))
+		ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0;
+
+	/* 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_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;
+
+	nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
+	if (nr != lpages)
+		goto out; /* 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;
+
+	/* okay - all conditions fulfilled */
+	ret = (unsigned long) page_address(pages[0]);
+
+ out:
+	if (pages) {
+		ptr = pages;
+		for (loop = lpages; loop > 0; loop--)
+			put_page(*ptr++);
+		kfree(pages);
+	}
+
+	return ret;
+}
+
+/*****************************************************************************/
+/*
+ * set up a mapping
+ */
+int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	return 0;
+}