75 lines
2.5 KiB
C
75 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* Copyright (C) 2010 Red Hat, Inc.
|
|
* Copyright (c) 2016-2018 Christoph Hellwig.
|
|
*/
|
|
#include <linux/module.h>
|
|
#include <linux/compiler.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/iomap.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;
|
|
if (WARN_ON(iomap.length == 0))
|
|
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;
|
|
}
|