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2023-12-09 b22da3d8526a935aa31e086e63f60ff3246cb61c 
 kernel/include/linux/bvec.h
....@@ -1,31 +1,32 @@
1
+/* SPDX-License-Identifier: GPL-2.0 */
12 /*
23  * bvec iterator
34  *
45  * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
5
- *
6
- * This program is free software; you can redistribute it and/or modify
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- * it under the terms of the GNU General Public License version 2 as
8
- * published by the Free Software Foundation.
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- *
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- * This program is distributed in the hope that it will be useful,
11
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
12
- *
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- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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- * GNU General Public License for more details.
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- *
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- * You should have received a copy of the GNU General Public Licens
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- * along with this program; if not, write to the Free Software
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- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
196  */
207 #ifndef __LINUX_BVEC_ITER_H
218 #define __LINUX_BVEC_ITER_H
229 
23
-#include <linux/kernel.h>
2410 #include <linux/bug.h>
2511 #include <linux/errno.h>
12
+#include <linux/limits.h>
13
+#include <linux/minmax.h>
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+#include <linux/mm.h>
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+#include <linux/types.h>
2616 
27
-/*
28
- * was unsigned short, but we might as well be ready for > 64kB I/O pages
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+struct page;
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+
19
+/**
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+ * struct bio_vec - a contiguous range of physical memory addresses
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+ * @bv_page:   First page associated with the address range.
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+ * @bv_len:    Number of bytes in the address range.
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+ * @bv_offset: Start of the address range relative to the start of @bv_page.
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+ *
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+ * The following holds for a bvec if n * PAGE_SIZE < bv_offset + bv_len:
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+ *
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+ *   nth_page(@bv_page, n) == @bv_page + n
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+ *
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+ * This holds because page_is_mergeable() checks the above property.
2930  */
3031 struct bio_vec {
3132 	struct page	*bv_page;
....@@ -40,10 +41,14 @@
4041 
4142 	unsigned int		bi_idx;		/* current index into bvl_vec */
4243 
43
-	unsigned int            bi_done;	/* number of bytes completed */
44
-
4544 	unsigned int            bi_bvec_done;	/* number of bytes completed in
4645 						   current bvec */
46
+};
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+
48
+struct bvec_iter_all {
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+	struct bio_vec	bv;
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+	int		idx;
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+	unsigned	done;
4752 };
4853 
4954 /*
....@@ -52,15 +57,38 @@
5257  */
5358 #define __bvec_iter_bvec(bvec, iter)	(&(bvec)[(iter).bi_idx])
5459 
55
-#define bvec_iter_page(bvec, iter)				\
60
+/* multi-page (mp_bvec) helpers */
61
+#define mp_bvec_iter_page(bvec, iter)				\
5662 	(__bvec_iter_bvec((bvec), (iter))->bv_page)
5763 
58
-#define bvec_iter_len(bvec, iter)				\
64
+#define mp_bvec_iter_len(bvec, iter)				\
5965 	min((iter).bi_size,					\
6066 	    __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
6167 
62
-#define bvec_iter_offset(bvec, iter)				\
68
+#define mp_bvec_iter_offset(bvec, iter)				\
6369 	(__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
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+
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+#define mp_bvec_iter_page_idx(bvec, iter)			\
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+	(mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE)
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+
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+#define mp_bvec_iter_bvec(bvec, iter)				\
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+((struct bio_vec) {						\
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+	.bv_page	= mp_bvec_iter_page((bvec), (iter)),	\
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+	.bv_len		= mp_bvec_iter_len((bvec), (iter)),	\
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+	.bv_offset	= mp_bvec_iter_offset((bvec), (iter)),	\
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+})
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+
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+/* For building single-page bvec in flight */
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+ #define bvec_iter_offset(bvec, iter)				\
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+	(mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE)
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+
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+#define bvec_iter_len(bvec, iter)				\
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+	min_t(unsigned, mp_bvec_iter_len((bvec), (iter)),		\
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+	      PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
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+
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+#define bvec_iter_page(bvec, iter)				\
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+	(mp_bvec_iter_page((bvec), (iter)) +			\
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+	 mp_bvec_iter_page_idx((bvec), (iter)))
6492 
6593 #define bvec_iter_bvec(bvec, iter)				\
6694 ((struct bio_vec) {						\
....@@ -72,50 +100,24 @@
72100 static inline bool bvec_iter_advance(const struct bio_vec *bv,
73101 		struct bvec_iter *iter, unsigned bytes)
74102 {
103
+	unsigned int idx = iter->bi_idx;
104
+
75105 	if (WARN_ONCE(bytes > iter->bi_size,
76106 		     "Attempted to advance past end of bvec iter\n")) {
77107 		iter->bi_size = 0;
78108 		return false;
79109 	}
80110 
81
-	while (bytes) {
82
-		unsigned iter_len = bvec_iter_len(bv, *iter);
83
-		unsigned len = min(bytes, iter_len);
111
+	iter->bi_size -= bytes;
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+	bytes += iter->bi_bvec_done;
84113 
85
-		bytes -= len;
86
-		iter->bi_size -= len;
87
-		iter->bi_bvec_done += len;
88
-		iter->bi_done += len;
89
-
90
-		if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
91
-			iter->bi_bvec_done = 0;
92
-			iter->bi_idx++;
93
-		}
114
+	while (bytes && bytes >= bv[idx].bv_len) {
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+		bytes -= bv[idx].bv_len;
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+		idx++;
94117 	}
95
-	return true;
96
-}
97118 
98
-static inline bool bvec_iter_rewind(const struct bio_vec *bv,
99
-				     struct bvec_iter *iter,
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-				     unsigned int bytes)
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-{
102
-	while (bytes) {
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-		unsigned len = min(bytes, iter->bi_bvec_done);
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-
105
-		if (iter->bi_bvec_done == 0) {
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-			if (WARN_ONCE(iter->bi_idx == 0,
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-				      "Attempted to rewind iter beyond "
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-				      "bvec's boundaries\n")) {
109
-				return false;
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-			}
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-			iter->bi_idx--;
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-			iter->bi_bvec_done = __bvec_iter_bvec(bv, *iter)->bv_len;
113
-			continue;
114
-		}
115
-		bytes -= len;
116
-		iter->bi_size += len;
117
-		iter->bi_bvec_done -= len;
118
-	}
119
+	iter->bi_idx = idx;
120
+	iter->bi_bvec_done = bytes;
119121 	return true;
120122 }
121123 
....@@ -141,4 +143,34 @@
141143 	.bi_bvec_done	= 0,						\
142144 }
143145 
146
+static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
147
+{
148
+	iter_all->done = 0;
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+	iter_all->idx = 0;
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+
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+	return &iter_all->bv;
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+}
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+
154
+static inline void bvec_advance(const struct bio_vec *bvec,
155
+				struct bvec_iter_all *iter_all)
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+{
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+	struct bio_vec *bv = &iter_all->bv;
158
+
159
+	if (iter_all->done) {
160
+		bv->bv_page++;
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+		bv->bv_offset = 0;
162
+	} else {
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+		bv->bv_page = bvec->bv_page + (bvec->bv_offset >> PAGE_SHIFT);
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+		bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
165
+	}
166
+	bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
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+			   bvec->bv_len - iter_all->done);
168
+	iter_all->done += bv->bv_len;
169
+
170
+	if (iter_all->done == bvec->bv_len) {
171
+		iter_all->idx++;
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+		iter_all->done = 0;
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+	}
174
+}
175
+
144176 #endif /* __LINUX_BVEC_ITER_H */