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bio_vec-backed iov_iter

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New variant of iov_iter - ITER_BVEC in iter->type, backed with
bio_vec array instead of iovec one.  Primitives taught to deal
with such beasts, __swap_write() switched to using that kind
of iov_iter.

Note that bio_vec is just a <page, offset, length> triple - there's
nothing block-specific about it.  I've left the definition where it
was, but took it from under ifdef CONFIG_BLOCK.

Next target: ->splice_write()...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2014-04-04 23:12:29 -04:00
parent 81055e584f
commit 62a8067a7f
5 changed files with 385 additions and 44 deletions
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14
include/linux/uio.h
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@@ -19,12 +19,21 @@ struct kvec {
size_t iov_len;
};
enum {
ITER_IOVEC = 0,
ITER_KVEC = 2,
ITER_BVEC = 4,
};
struct iov_iter {
int type;
const struct iovec *iov;
unsigned long nr_segs;
size_t iov_offset;
size_t count;
union {
const struct iovec *iov;
const struct bio_vec *bvec;
};
unsigned long nr_segs;
};
/*
@@ -54,6 +63,7 @@ static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
}
#define iov_for_each(iov, iter, start) \
if (!((start).type & ITER_BVEC)) \
for (iter = (start); \
(iter).count && \
((iov = iov_iter_iovec(&(iter))), 1); \