1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2010 Red Hat, Inc.
4 * Copyright (c) 2016-2021 Christoph Hellwig.
5 */
6 #include <linux/fs.h>
7 #include <linux/iomap.h>
8 #include "trace.h"
9
10 /*
11 * Advance to the next range we need to map.
12 *
13 * If the iomap is marked IOMAP_F_STALE, it means the existing map was not fully
14 * processed - it was aborted because the extent the iomap spanned may have been
15 * changed during the operation. In this case, the iteration behaviour is to
16 * remap the unprocessed range of the iter, and that means we may need to remap
17 * even when we've made no progress (i.e. iter->processed = 0). Hence the
18 * "finished iterating" case needs to distinguish between
19 * (processed = 0) meaning we are done and (processed = 0 && stale) meaning we
20 * need to remap the entire remaining range.
21 */
22 static inline int iomap_iter_advance(struct iomap_iter *iter)
23 {
24 bool stale = iter->iomap.flags & IOMAP_F_STALE;
25
26 /* handle the previous iteration (if any) */
27 if (iter->iomap.length) {
28 if (iter->processed < 0)
29 return iter->processed;
30 if (!iter->processed && !stale)
31 return 0;
32 if (WARN_ON_ONCE(iter->processed > iomap_length(iter)))
33 return -EIO;
34 iter->pos += iter->processed;
35 iter->len -= iter->processed;
36 if (!iter->len)
37 return 0;
38 }
39
40 /* clear the state for the next iteration */
41 iter->processed = 0;
42 memset(&iter->iomap, 0, sizeof(iter->iomap));
43 memset(&iter->srcmap, 0, sizeof(iter->srcmap));
44 return 1;
45 }
46
47 static inline void iomap_iter_done(struct iomap_iter *iter)
48 {
49 WARN_ON_ONCE(iter->iomap.offset > iter->pos);
50 WARN_ON_ONCE(iter->iomap.length == 0);
51 WARN_ON_ONCE(iter->iomap.offset + iter->iomap.length <= iter->pos);
52 WARN_ON_ONCE(iter->iomap.flags & IOMAP_F_STALE);
53
54 trace_iomap_iter_dstmap(iter->inode, &iter->iomap);
55 if (iter->srcmap.type != IOMAP_HOLE)
56 trace_iomap_iter_srcmap(iter->inode, &iter->srcmap);
57 }
58
59 /**
60 * iomap_iter - iterate over a ranges in a file
61 * @iter: iteration structue
62 * @ops: iomap ops provided by the file system
63 *
64 * Iterate over filesystem-provided space mappings for the provided file range.
65 *
66 * This function handles cleanup of resources acquired for iteration when the
67 * filesystem indicates there are no more space mappings, which means that this
68 * function must be called in a loop that continues as long it returns a
69 * positive value. If 0 or a negative value is returned, the caller must not
70 * return to the loop body. Within a loop body, there are two ways to break out
71 * of the loop body: leave @iter.processed unchanged, or set it to a negative
72 * errno.
73 */
74 int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
75 {
76 int ret;
77
78 if (iter->iomap.length && ops->iomap_end) {
79 ret = ops->iomap_end(iter->inode, iter->pos, iomap_length(iter),
80 iter->processed > 0 ? iter->processed : 0,
81 iter->flags, &iter->iomap);
82 if (ret < 0 && !iter->processed)
83 return ret;
84 }
85
86 trace_iomap_iter(iter, ops, _RET_IP_);
87 ret = iomap_iter_advance(iter);
88 if (ret <= 0)
89 return ret;
90
91 ret = ops->iomap_begin(iter->inode, iter->pos, iter->len, iter->flags,
92 &iter->iomap, &iter->srcmap);
93 if (ret < 0)
94 return ret;
95 iomap_iter_done(iter);
96 return 1;
97 }
98
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