--- /dev/null
+/* 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 <linux/slab.h>
+
+#include <asm/uaccess.h>
+#include "internal.h"
+
+static int ramfs_nommu_setattr(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 = generic_file_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;
+
+ /* 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);
+ 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 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 = inode_change_ok(inode, 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(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, loop, ret;
+ struct inode *inode = file_inode(file);
+ 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 = kcalloc(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
+ */
+static 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;
+}
Code Review / kvmfornfv.git / blobdiff