1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
|
// 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>
#include <linux/uaccess.h>
#include <linux/gfp.h>
#include <linux/migrate.h>
#include <linux/mm.h>
#include <linux/mm_inline.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/pagevec.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;
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;
}
|
