/*
* Copyright (C) 2010 Red Hat, Inc.
* Copyright (c) 2016 Christoph Hellwig.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*/
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/iomap.h>
#include <linux/uaccess.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/dax.h>
#include <linux/sched/signal.h>
#include "internal.h"
/*
* Execute a iomap write on a segment of the mapping that spans a
* contiguous range of pages that have identical block mapping state.
*
* This avoids the need to map pages individually, do individual allocations
* for each page and most importantly avoid the need for filesystem specific
* locking per page. Instead, all the operations are amortised over the entire
* range of pages. It is assumed that the filesystems will lock whatever
* resources they require in the iomap_begin call, and release them in the
* iomap_end call.
*/
loff_t
iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
const struct iomap_ops *ops, void *data, iomap_actor_t actor)
{
struct iomap iomap = { 0 };
loff_t written = 0, ret;
/*
* Need to map a range from start position for length bytes. This can
* span multiple pages - it is only guaranteed to return a range of a
* single type of pages (e.g. all into a hole, all mapped or all
* unwritten). Failure at this point has nothing to undo.
*
* If allocation is required for this range, reserve the space now so
* that the allocation is guaranteed to succeed later on. Once we copy
* the data into the page cache pages, then we cannot fail otherwise we
* expose transient stale data. If the reserve fails, we can safely
* back out at this point as there is nothing to undo.
*/
ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
if (ret)
return ret;
if (WARN_ON(iomap.offset > pos))
return -EIO;
/*
* Cut down the length to the one actually provided by the filesystem,
* as it might not be able to give us the whole size that we requested.
*/
if (iomap.offset + iomap.length < pos + length)
length = iomap.offset + iomap.length - pos;
/*
* Now that we have guaranteed that the space allocation will succeed.
* we can do the copy-in page by page without having to worry about
* failures exposing transient data.
*/
written = actor(inode, pos, length, data, &iomap);
/*
* Now the data has been copied, commit the range we've copied. This
* should not fail unless the filesystem has had a fatal error.
*/
if (ops->iomap_end) {
ret = ops->iomap_end(inode, pos, length,
written > 0 ? written : 0,
flags, &iomap);
}
return written ? written : ret;
}
static void
iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
{
loff_t i_size = i_size_read(inode);
/*
* Only truncate newly allocated pages beyoned EOF, even if the
* write started inside the existing inode size.
*/
if (pos + len > i_size)
truncate_pagecache_range(inode, max(pos, i_size), pos + len);
}
static int
iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
struct page **pagep, struct iomap *iomap)
{
pgoff_t index = pos >> PAGE_SHIFT;
struct page *page;
int status = 0;
BUG_ON(pos + len > iomap->offset + iomap->length);
if (fatal_signal_pending(current))
return -EINTR;
page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
if (!page)
return -ENOMEM;
status = __block_write_begin_int(page, pos, len, NULL, iomap);
if (unlikely(status)) {
unlock_page(page);
put_page(page);
page = NULL;
iomap_write_failed(inode, pos, len);
}
*pagep = page;
return status;
}
static int
iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
unsigned copied, struct page *page)
{
int ret;
ret = generic_write_end(NULL, inode