v4.19.13 snapshot.
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
new file mode 100644
index 0000000..fe7a22d
--- /dev/null
+++ b/include/linux/bvec.h
@@ -0,0 +1,137 @@
+/*
+ * bvec iterator
+ *
+ * Copyright (C) 2001 Ming Lei <ming.lei@canonical.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that 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.
+ *
+ * You should have received a copy of the GNU General Public Licens
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-
+ */
+#ifndef __LINUX_BVEC_ITER_H
+#define __LINUX_BVEC_ITER_H
+
+#include <linux/kernel.h>
+#include <linux/bug.h>
+#include <linux/errno.h>
+
+/*
+ * was unsigned short, but we might as well be ready for > 64kB I/O pages
+ */
+struct bio_vec {
+ struct page *bv_page;
+ unsigned int bv_len;
+ unsigned int bv_offset;
+};
+
+struct bvec_iter {
+ sector_t bi_sector; /* device address in 512 byte
+ sectors */
+ unsigned int bi_size; /* residual I/O count */
+
+ unsigned int bi_idx; /* current index into bvl_vec */
+
+ unsigned int bi_done; /* number of bytes completed */
+
+ unsigned int bi_bvec_done; /* number of bytes completed in
+ current bvec */
+};
+
+/*
+ * various member access, note that bio_data should of course not be used
+ * on highmem page vectors
+ */
+#define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx])
+
+#define bvec_iter_page(bvec, iter) \
+ (__bvec_iter_bvec((bvec), (iter))->bv_page)
+
+#define bvec_iter_len(bvec, iter) \
+ min((iter).bi_size, \
+ __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done)
+
+#define bvec_iter_offset(bvec, iter) \
+ (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done)
+
+#define bvec_iter_bvec(bvec, iter) \
+((struct bio_vec) { \
+ .bv_page = bvec_iter_page((bvec), (iter)), \
+ .bv_len = bvec_iter_len((bvec), (iter)), \
+ .bv_offset = bvec_iter_offset((bvec), (iter)), \
+})
+
+static inline bool bvec_iter_advance(const struct bio_vec *bv,
+ struct bvec_iter *iter, unsigned bytes)
+{
+ if (WARN_ONCE(bytes > iter->bi_size,
+ "Attempted to advance past end of bvec iter\n")) {
+ iter->bi_size = 0;
+ return false;
+ }
+
+ while (bytes) {
+ unsigned iter_len = bvec_iter_len(bv, *iter);
+ unsigned len = min(bytes, iter_len);
+
+ bytes -= len;
+ iter->bi_size -= len;
+ iter->bi_bvec_done += len;
+ iter->bi_done += len;
+
+ if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
+ iter->bi_bvec_done = 0;
+ iter->bi_idx++;
+ }
+ }
+ return true;
+}
+
+static inline bool bvec_iter_rewind(const struct bio_vec *bv,
+ struct bvec_iter *iter,
+ unsigned int bytes)
+{
+ while (bytes) {
+ unsigned len = min(bytes, iter->bi_bvec_done);
+
+ if (iter->bi_bvec_done == 0) {
+ if (WARN_ONCE(iter->bi_idx == 0,
+ "Attempted to rewind iter beyond "
+ "bvec's boundaries\n")) {
+ return false;
+ }
+ iter->bi_idx--;
+ iter->bi_bvec_done = __bvec_iter_bvec(bv, *iter)->bv_len;
+ continue;
+ }
+ bytes -= len;
+ iter->bi_size += len;
+ iter->bi_bvec_done -= len;
+ }
+ return true;
+}
+
+#define for_each_bvec(bvl, bio_vec, iter, start) \
+ for (iter = (start); \
+ (iter).bi_size && \
+ ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
+ bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
+
+/* for iterating one bio from start to end */
+#define BVEC_ITER_ALL_INIT (struct bvec_iter) \
+{ \
+ .bi_sector = 0, \
+ .bi_size = UINT_MAX, \
+ .bi_idx = 0, \
+ .bi_bvec_done = 0, \
+}
+
+#endif /* __LINUX_BVEC_ITER_H */