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iov_iter: reorder handling of flavours in primitives 

iovec is the most common one; test it first and test explicitly,
rather than "not anything else".  Replace all flavour checks with
use of iov_iter_is_...() helpers.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2021-06-02 17:25:59 -04:00
parent 4b6c132b7d
commit 28f38db7ed
1 changed files with 59 additions and 60 deletions
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115
lib/iov_iter.c
View File

@ -117,22 +117,21 @@
#define iterate_all_kinds(i, n, v, I, B, K, X) { \
if (likely(n)) { \
size_t skip = i->iov_offset; \
if (unlikely(i->type & ITER_BVEC)) { \
struct bio_vec v; \
struct bvec_iter __bi; \
iterate_bvec(i, n, v, __bi, skip, (B)) \
} else if (unlikely(i->type & ITER_KVEC)) { \
const struct kvec *kvec; \
struct kvec v; \
iterate_kvec(i, n, v, kvec, skip, (K)) \
} else if (unlikely(i->type & ITER_DISCARD)) { \
} else if (unlikely(i->type & ITER_XARRAY)) { \
struct bio_vec v; \
iterate_xarray(i, n, v, skip, (X)); \
} else { \
if (likely(iter_is_iovec(i))) { \
const struct iovec *iov; \
struct iovec v; \
iterate_iovec(i, n, v, iov, skip, (I)) \
} else if (iov_iter_is_bvec(i)) { \
struct bio_vec v; \
struct bvec_iter __bi; \
iterate_bvec(i, n, v, __bi, skip, (B)) \
} else if (iov_iter_is_kvec(i)) { \
const struct kvec *kvec; \
struct kvec v; \
iterate_kvec(i, n, v, kvec, skip, (K)) \
} else if (iov_iter_is_xarray(i)) { \
struct bio_vec v; \
iterate_xarray(i, n, v, skip, (X)); \
} \
} \
}
@ -142,30 +141,7 @@
n = i->count; \
if (i->count) { \
size_t skip = i->iov_offset; \
if (unlikely(i->type & ITER_BVEC)) { \
const struct bio_vec *bvec = i->bvec; \
struct bio_vec v; \
struct bvec_iter __bi; \
iterate_bvec(i, n, v, __bi, skip, (B)) \
i->bvec = __bvec_iter_bvec(i->bvec, __bi); \
i->nr_segs -= i->bvec - bvec; \
skip = __bi.bi_bvec_done; \
} else if (unlikely(i->type & ITER_KVEC)) { \
const struct kvec *kvec; \
struct kvec v; \
iterate_kvec(i, n, v, kvec, skip, (K)) \
if (skip == kvec->iov_len) { \
kvec++; \
skip = 0; \
} \
i->nr_segs -= kvec - i->kvec; \
i->kvec = kvec; \
} else if (unlikely(i->type & ITER_DISCARD)) { \
skip += n; \
} else if (unlikely(i->type & ITER_XARRAY)) { \
struct bio_vec v; \
iterate_xarray(i, n, v, skip, (X)) \
} else { \
if (likely(iter_is_iovec(i))) { \
const struct iovec *iov; \
struct iovec v; \
iterate_iovec(i, n, v, iov, skip, (I)) \
@ -175,6 +151,29 @@
} \
i->nr_segs -= iov - i->iov; \
i->iov = iov; \
} else if (iov_iter_is_bvec(i)) { \
const struct bio_vec *bvec = i->bvec; \
struct bio_vec v; \
struct bvec_iter __bi; \
iterate_bvec(i, n, v, __bi, skip, (B)) \
i->bvec = __bvec_iter_bvec(i->bvec, __bi); \
i->nr_segs -= i->bvec - bvec; \
skip = __bi.bi_bvec_done; \
} else if (iov_iter_is_kvec(i)) { \
const struct kvec *kvec; \
struct kvec v; \
iterate_kvec(i, n, v, kvec, skip, (K)) \
if (skip == kvec->iov_len) { \
kvec++; \
skip = 0; \
} \
i->nr_segs -= kvec - i->kvec; \
i->kvec = kvec; \
} else if (iov_iter_is_xarray(i)) { \
struct bio_vec v; \
iterate_xarray(i, n, v, skip, (X)) \
} else if (iov_iter_is_discard(i)) { \
skip += n; \
} \
i->count -= n; \
i->iov_offset = skip; \
@ -905,20 +904,24 @@ static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
static size_t __copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
if (i->type & (ITER_BVEC | ITER_KVEC | ITER_XARRAY)) {
if (likely(iter_is_iovec(i)))
return copy_page_to_iter_iovec(page, offset, bytes, i);
if (iov_iter_is_bvec(i) || iov_iter_is_kvec(i) || iov_iter_is_xarray(i)) {
void *kaddr = kmap_atomic(page);
size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
kunmap_atomic(kaddr);
return wanted;
} else if (unlikely(iov_iter_is_discard(i))) {
}
if (iov_iter_is_pipe(i))
return copy_page_to_iter_pipe(page, offset, bytes, i);
if (unlikely(iov_iter_is_discard(i))) {
if (unlikely(i->count < bytes))
bytes = i->count;
i->count -= bytes;
return bytes;
} else if (likely(!iov_iter_is_pipe(i)))
return copy_page_to_iter_iovec(page, offset, bytes, i);
else
return copy_page_to_iter_pipe(page, offset, bytes, i);
}
WARN_ON(1);
return 0;
}
size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
@ -951,17 +954,16 @@ size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
{
if (unlikely(!page_copy_sane(page, offset, bytes)))
return 0;
if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
WARN_ON(1);
return 0;
}
if (i->type & (ITER_BVEC | ITER_KVEC | ITER_XARRAY)) {
if (likely(iter_is_iovec(i)))
return copy_page_from_iter_iovec(page, offset, bytes, i);
if (iov_iter_is_bvec(i) || iov_iter_is_kvec(i) || iov_iter_is_xarray(i)) {
void *kaddr = kmap_atomic(page);
size_t wanted = _copy_from_iter(kaddr + offset, bytes, i);
kunmap_atomic(kaddr);
return wanted;
} else
return copy_page_from_iter_iovec(page, offset, bytes, i);
}
WARN_ON(1);
return 0;
}
EXPORT_SYMBOL(copy_page_from_iter);
@ -1203,16 +1205,13 @@ EXPORT_SYMBOL(iov_iter_revert);
*/
size_t iov_iter_single_seg_count(const struct iov_iter *i)
{
if (unlikely(iov_iter_is_pipe(i)))
return i->count; // it is a silly place, anyway
if (i->nr_segs == 1)
return i->count;
if (unlikely(iov_iter_is_discard(i) || iov_iter_is_xarray(i)))
return i->count;
if (i->nr_segs > 1) {
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return min(i->count, i->iov->iov_len - i->iov_offset);
if (iov_iter_is_bvec(i))
return min(i->count, i->bvec->bv_len - i->iov_offset);
else
return min(i->count, i->iov->iov_len - i->iov_offset);
}
return i->count;
}
EXPORT_SYMBOL(iov_iter_single_seg_count);