![Nick Piggin](/assets/img/avatar_default.png)
Nonlinear mappings are (AFAIKS) simply a virtual memory concept that encodes the virtual address -> file offset differently from linear mappings. ->populate is a layering violation because the filesystem/pagecache code should need to know anything about the virtual memory mapping. The hitch here is that the ->nopage handler didn't pass down enough information (ie. pgoff). But it is more logical to pass pgoff rather than have the ->nopage function calculate it itself anyway (because that's a similar layering violation). Having the populate handler install the pte itself is likewise a nasty thing to be doing. This patch introduces a new fault handler that replaces ->nopage and ->populate and (later) ->nopfn. Most of the old mechanism is still in place so there is a lot of duplication and nice cleanups that can be removed if everyone switches over. The rationale for doing this in the first place is that nonlinear mappings are subject to the pagefault vs invalidate/truncate race too, and it seemed stupid to duplicate the synchronisation logic rather than just consolidate the two. After this patch, MAP_NONBLOCK no longer sets up ptes for pages present in pagecache. Seems like a fringe functionality anyway. NOPAGE_REFAULT is removed. This should be implemented with ->fault, and no users have hit mainline yet. [akpm@linux-foundation.org: cleanup] [randy.dunlap@oracle.com: doc. fixes for readahead] [akpm@linux-foundation.org: build fix] Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Cc: Mark Fasheh <mark.fasheh@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
449 lines
10 KiB
C
449 lines
10 KiB
C
/*
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* linux/mm/filemap_xip.c
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*
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* Copyright (C) 2005 IBM Corporation
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* Author: Carsten Otte <cotte@de.ibm.com>
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*
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* derived from linux/mm/filemap.c - Copyright (C) Linus Torvalds
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*
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*/
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#include <linux/fs.h>
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#include <linux/pagemap.h>
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#include <linux/module.h>
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#include <linux/uio.h>
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#include <linux/rmap.h>
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#include <linux/sched.h>
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#include <asm/tlbflush.h>
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#include "filemap.h"
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/*
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* We do use our own empty page to avoid interference with other users
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* of ZERO_PAGE(), such as /dev/zero
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*/
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static struct page *__xip_sparse_page;
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static struct page *xip_sparse_page(void)
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{
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if (!__xip_sparse_page) {
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unsigned long zeroes = get_zeroed_page(GFP_HIGHUSER);
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if (zeroes) {
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static DEFINE_SPINLOCK(xip_alloc_lock);
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spin_lock(&xip_alloc_lock);
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if (!__xip_sparse_page)
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__xip_sparse_page = virt_to_page(zeroes);
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else
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free_page(zeroes);
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spin_unlock(&xip_alloc_lock);
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}
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}
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return __xip_sparse_page;
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}
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/*
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* This is a file read routine for execute in place files, and uses
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* the mapping->a_ops->get_xip_page() function for the actual low-level
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* stuff.
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*
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* Note the struct file* is not used at all. It may be NULL.
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*/
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static void
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do_xip_mapping_read(struct address_space *mapping,
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struct file_ra_state *_ra,
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struct file *filp,
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loff_t *ppos,
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read_descriptor_t *desc,
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read_actor_t actor)
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{
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struct inode *inode = mapping->host;
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unsigned long index, end_index, offset;
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loff_t isize;
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BUG_ON(!mapping->a_ops->get_xip_page);
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index = *ppos >> PAGE_CACHE_SHIFT;
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offset = *ppos & ~PAGE_CACHE_MASK;
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isize = i_size_read(inode);
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if (!isize)
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goto out;
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end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
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for (;;) {
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struct page *page;
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unsigned long nr, ret;
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/* nr is the maximum number of bytes to copy from this page */
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nr = PAGE_CACHE_SIZE;
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if (index >= end_index) {
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if (index > end_index)
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goto out;
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nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
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if (nr <= offset) {
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goto out;
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}
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}
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nr = nr - offset;
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page = mapping->a_ops->get_xip_page(mapping,
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index*(PAGE_SIZE/512), 0);
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if (!page)
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goto no_xip_page;
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if (unlikely(IS_ERR(page))) {
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if (PTR_ERR(page) == -ENODATA) {
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/* sparse */
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page = ZERO_PAGE(0);
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} else {
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desc->error = PTR_ERR(page);
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goto out;
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}
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}
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/* If users can be writing to this page using arbitrary
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* virtual addresses, take care about potential aliasing
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* before reading the page on the kernel side.
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*/
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if (mapping_writably_mapped(mapping))
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flush_dcache_page(page);
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/*
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* Ok, we have the page, so now we can copy it to user space...
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*
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* The actor routine returns how many bytes were actually used..
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* NOTE! This may not be the same as how much of a user buffer
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* we filled up (we may be padding etc), so we can only update
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* "pos" here (the actor routine has to update the user buffer
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* pointers and the remaining count).
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*/
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ret = actor(desc, page, offset, nr);
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offset += ret;
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index += offset >> PAGE_CACHE_SHIFT;
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offset &= ~PAGE_CACHE_MASK;
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if (ret == nr && desc->count)
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continue;
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goto out;
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no_xip_page:
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/* Did not get the page. Report it */
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desc->error = -EIO;
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goto out;
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}
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out:
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*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
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if (filp)
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file_accessed(filp);
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}
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ssize_t
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xip_file_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
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{
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read_descriptor_t desc;
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if (!access_ok(VERIFY_WRITE, buf, len))
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return -EFAULT;
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desc.written = 0;
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desc.arg.buf = buf;
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desc.count = len;
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desc.error = 0;
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do_xip_mapping_read(filp->f_mapping, &filp->f_ra, filp,
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ppos, &desc, file_read_actor);
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if (desc.written)
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return desc.written;
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else
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return desc.error;
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}
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EXPORT_SYMBOL_GPL(xip_file_read);
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/*
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* __xip_unmap is invoked from xip_unmap and
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* xip_write
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*
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* This function walks all vmas of the address_space and unmaps the
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* __xip_sparse_page when found at pgoff.
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*/
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static void
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__xip_unmap (struct address_space * mapping,
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unsigned long pgoff)
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{
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struct vm_area_struct *vma;
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struct mm_struct *mm;
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struct prio_tree_iter iter;
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unsigned long address;
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pte_t *pte;
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pte_t pteval;
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spinlock_t *ptl;
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struct page *page;
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page = __xip_sparse_page;
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if (!page)
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return;
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spin_lock(&mapping->i_mmap_lock);
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vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
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mm = vma->vm_mm;
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address = vma->vm_start +
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((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
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BUG_ON(address < vma->vm_start || address >= vma->vm_end);
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pte = page_check_address(page, mm, address, &ptl);
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if (pte) {
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/* Nuke the page table entry. */
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flush_cache_page(vma, address, pte_pfn(*pte));
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pteval = ptep_clear_flush(vma, address, pte);
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page_remove_rmap(page, vma);
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dec_mm_counter(mm, file_rss);
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BUG_ON(pte_dirty(pteval));
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pte_unmap_unlock(pte, ptl);
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page_cache_release(page);
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}
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}
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spin_unlock(&mapping->i_mmap_lock);
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}
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/*
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* xip_fault() is invoked via the vma operations vector for a
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* mapped memory region to read in file data during a page fault.
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*
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* This function is derived from filemap_fault, but used for execute in place
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*/
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static struct page *xip_file_fault(struct vm_area_struct *area,
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struct fault_data *fdata)
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{
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struct file *file = area->vm_file;
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struct address_space *mapping = file->f_mapping;
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struct inode *inode = mapping->host;
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struct page *page;
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pgoff_t size;
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/* XXX: are VM_FAULT_ codes OK? */
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size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
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if (fdata->pgoff >= size) {
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fdata->type = VM_FAULT_SIGBUS;
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return NULL;
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}
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page = mapping->a_ops->get_xip_page(mapping,
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fdata->pgoff*(PAGE_SIZE/512), 0);
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if (!IS_ERR(page))
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goto out;
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if (PTR_ERR(page) != -ENODATA) {
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fdata->type = VM_FAULT_OOM;
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return NULL;
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}
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/* sparse block */
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if ((area->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
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(area->vm_flags & (VM_SHARED| VM_MAYSHARE)) &&
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(!(mapping->host->i_sb->s_flags & MS_RDONLY))) {
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/* maybe shared writable, allocate new block */
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page = mapping->a_ops->get_xip_page(mapping,
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fdata->pgoff*(PAGE_SIZE/512), 1);
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if (IS_ERR(page)) {
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fdata->type = VM_FAULT_SIGBUS;
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return NULL;
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}
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/* unmap page at pgoff from all other vmas */
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__xip_unmap(mapping, fdata->pgoff);
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} else {
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/* not shared and writable, use xip_sparse_page() */
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page = xip_sparse_page();
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if (!page) {
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fdata->type = VM_FAULT_OOM;
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return NULL;
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}
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}
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out:
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fdata->type = VM_FAULT_MINOR;
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page_cache_get(page);
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return page;
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}
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static struct vm_operations_struct xip_file_vm_ops = {
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.fault = xip_file_fault,
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};
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int xip_file_mmap(struct file * file, struct vm_area_struct * vma)
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{
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BUG_ON(!file->f_mapping->a_ops->get_xip_page);
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file_accessed(file);
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vma->vm_ops = &xip_file_vm_ops;
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vma->vm_flags |= VM_CAN_NONLINEAR;
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return 0;
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}
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EXPORT_SYMBOL_GPL(xip_file_mmap);
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static ssize_t
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__xip_file_write(struct file *filp, const char __user *buf,
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size_t count, loff_t pos, loff_t *ppos)
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{
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struct address_space * mapping = filp->f_mapping;
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const struct address_space_operations *a_ops = mapping->a_ops;
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struct inode *inode = mapping->host;
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long status = 0;
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struct page *page;
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size_t bytes;
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ssize_t written = 0;
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BUG_ON(!mapping->a_ops->get_xip_page);
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do {
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unsigned long index;
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unsigned long offset;
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size_t copied;
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offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
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index = pos >> PAGE_CACHE_SHIFT;
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bytes = PAGE_CACHE_SIZE - offset;
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if (bytes > count)
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bytes = count;
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/*
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* Bring in the user page that we will copy from _first_.
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* Otherwise there's a nasty deadlock on copying from the
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* same page as we're writing to, without it being marked
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* up-to-date.
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*/
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fault_in_pages_readable(buf, bytes);
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page = a_ops->get_xip_page(mapping,
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index*(PAGE_SIZE/512), 0);
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if (IS_ERR(page) && (PTR_ERR(page) == -ENODATA)) {
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/* we allocate a new page unmap it */
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page = a_ops->get_xip_page(mapping,
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index*(PAGE_SIZE/512), 1);
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if (!IS_ERR(page))
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/* unmap page at pgoff from all other vmas */
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__xip_unmap(mapping, index);
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}
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if (IS_ERR(page)) {
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status = PTR_ERR(page);
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break;
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}
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copied = filemap_copy_from_user(page, offset, buf, bytes);
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flush_dcache_page(page);
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if (likely(copied > 0)) {
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status = copied;
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if (status >= 0) {
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written += status;
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count -= status;
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pos += status;
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buf += status;
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}
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}
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if (unlikely(copied != bytes))
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if (status >= 0)
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status = -EFAULT;
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if (status < 0)
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break;
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} while (count);
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*ppos = pos;
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/*
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* No need to use i_size_read() here, the i_size
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* cannot change under us because we hold i_mutex.
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*/
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if (pos > inode->i_size) {
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i_size_write(inode, pos);
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mark_inode_dirty(inode);
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}
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return written ? written : status;
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}
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ssize_t
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xip_file_write(struct file *filp, const char __user *buf, size_t len,
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loff_t *ppos)
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{
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struct address_space *mapping = filp->f_mapping;
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struct inode *inode = mapping->host;
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size_t count;
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loff_t pos;
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ssize_t ret;
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mutex_lock(&inode->i_mutex);
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if (!access_ok(VERIFY_READ, buf, len)) {
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ret=-EFAULT;
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goto out_up;
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}
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pos = *ppos;
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count = len;
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vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
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/* We can write back this queue in page reclaim */
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current->backing_dev_info = mapping->backing_dev_info;
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ret = generic_write_checks(filp, &pos, &count, S_ISBLK(inode->i_mode));
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if (ret)
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goto out_backing;
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if (count == 0)
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goto out_backing;
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ret = remove_suid(filp->f_path.dentry);
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if (ret)
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goto out_backing;
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file_update_time(filp);
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ret = __xip_file_write (filp, buf, count, pos, ppos);
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out_backing:
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current->backing_dev_info = NULL;
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out_up:
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mutex_unlock(&inode->i_mutex);
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return ret;
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}
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EXPORT_SYMBOL_GPL(xip_file_write);
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/*
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* truncate a page used for execute in place
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* functionality is analog to block_truncate_page but does use get_xip_page
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* to get the page instead of page cache
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*/
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int
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xip_truncate_page(struct address_space *mapping, loff_t from)
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{
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pgoff_t index = from >> PAGE_CACHE_SHIFT;
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unsigned offset = from & (PAGE_CACHE_SIZE-1);
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unsigned blocksize;
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unsigned length;
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struct page *page;
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BUG_ON(!mapping->a_ops->get_xip_page);
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blocksize = 1 << mapping->host->i_blkbits;
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length = offset & (blocksize - 1);
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/* Block boundary? Nothing to do */
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if (!length)
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return 0;
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length = blocksize - length;
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page = mapping->a_ops->get_xip_page(mapping,
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index*(PAGE_SIZE/512), 0);
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if (!page)
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return -ENOMEM;
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if (unlikely(IS_ERR(page))) {
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if (PTR_ERR(page) == -ENODATA)
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/* Hole? No need to truncate */
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return 0;
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else
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return PTR_ERR(page);
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}
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zero_user_page(page, offset, length, KM_USER0);
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return 0;
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}
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EXPORT_SYMBOL_GPL(xip_truncate_page);
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