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iov_iter.c: iterate_and_advance

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same as iterate_all_kinds, but iterator is moved to the position past
the last byte we'd handled.

iov_iter_advance() converted to it

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2014-11-27 13:59:45 -05:00
parent 04a311655b
commit 7ce2a91e51
1 changed files with 28 additions and 76 deletions
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104
mm/iov_iter.c
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@ -70,6 +70,33 @@
} \
}
#define iterate_and_advance(i, n, v, I, B) { \
size_t skip = i->iov_offset; \
if (unlikely(i->type & ITER_BVEC)) { \
const struct bio_vec *bvec; \
struct bio_vec v; \
iterate_bvec(i, n, v, bvec, skip, (B)) \
if (skip == bvec->bv_len) { \
bvec++; \
skip = 0; \
} \
i->nr_segs -= bvec - i->bvec; \
i->bvec = bvec; \
} else { \
const struct iovec *iov; \
struct iovec v; \
iterate_iovec(i, n, v, iov, skip, (I)) \
if (skip == iov->iov_len) { \
iov++; \
skip = 0; \
} \
i->nr_segs -= iov - i->iov; \
i->iov = iov; \
} \
i->count -= n; \
i->iov_offset = skip; \
}
static size_t copy_to_iter_iovec(void *from, size_t bytes, struct iov_iter *i)
{
size_t skip, copy, left, wanted;
@ -366,42 +393,6 @@ static size_t zero_iovec(size_t bytes, struct iov_iter *i)
return wanted - bytes;
}
static void advance_iovec(struct iov_iter *i, size_t bytes)
{
BUG_ON(i->count < bytes);
if (likely(i->nr_segs == 1)) {
i->iov_offset += bytes;
i->count -= bytes;
} else {
const struct iovec *iov = i->iov;
size_t base = i->iov_offset;
unsigned long nr_segs = i->nr_segs;
/*
* The !iov->iov_len check ensures we skip over unlikely
* zero-length segments (without overruning the iovec).
*/
while (bytes || unlikely(i->count && !iov->iov_len)) {
int copy;
copy = min(bytes, iov->iov_len - base);
BUG_ON(!i->count || i->count < copy);
i->count -= copy;
bytes -= copy;
base += copy;
if (iov->iov_len == base) {
iov++;
nr_segs--;
base = 0;
}
}
i->iov = iov;
i->iov_offset = base;
i->nr_segs = nr_segs;
}
}
/*
* Fault in the first iovec of the given iov_iter, to a maximum length
* of bytes. Returns 0 on success, or non-zero if the memory could not be
@ -685,42 +676,6 @@ static size_t zero_bvec(size_t bytes, struct iov_iter *i)
return wanted - bytes;
}
static void advance_bvec(struct iov_iter *i, size_t bytes)
{
BUG_ON(i->count < bytes);
if (likely(i->nr_segs == 1)) {
i->iov_offset += bytes;
i->count -= bytes;
} else {
const struct bio_vec *bvec = i->bvec;
size_t base = i->iov_offset;
unsigned long nr_segs = i->nr_segs;
/*
* The !iov->iov_len check ensures we skip over unlikely
* zero-length segments (without overruning the iovec).
*/
while (bytes || unlikely(i->count && !bvec->bv_len)) {
int copy;
copy = min(bytes, bvec->bv_len - base);
BUG_ON(!i->count || i->count < copy);
i->count -= copy;
bytes -= copy;
base += copy;
if (bvec->bv_len == base) {
bvec++;
nr_segs--;
base = 0;
}
}
i->bvec = bvec;
i->iov_offset = base;
i->nr_segs = nr_segs;
}
}
static ssize_t get_pages_bvec(struct iov_iter *i,
struct page **pages, size_t maxsize, unsigned maxpages,
size_t *start)
@ -849,10 +804,7 @@ EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
void iov_iter_advance(struct iov_iter *i, size_t size)
{
if (i->type & ITER_BVEC)
advance_bvec(i, size);
else
advance_iovec(i, size);
iterate_and_advance(i, size, v, 0, 0)
}
EXPORT_SYMBOL(iov_iter_advance);