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iov_iter: separate direction from flavour

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Instead of having them mixed in iter->type, use separate ->iter_type
and ->data_source (u8 and bool resp.)  And don't bother with (pseudo-)
bitmap for the former - microoptimizations from being able to check
if the flavour is one of two values are not worth the confusion for
optimizer.  It can't prove that we never get e.g. ITER_IOVEC | ITER_PIPE,
so we end up with extra headache.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2021-04-22 14:50:39 -04:00
parent 556351c1c0
commit 8cd54c1c84
2 changed files with 58 additions and 51 deletions
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24
include/linux/uio.h
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@ -19,21 +19,17 @@ struct kvec {
enum iter_type {
/* iter types */
ITER_IOVEC = 4,
ITER_KVEC = 8,
ITER_BVEC = 16,
ITER_PIPE = 32,
ITER_DISCARD = 64,
ITER_XARRAY = 128,
ITER_IOVEC,
ITER_KVEC,
ITER_BVEC,
ITER_PIPE,
ITER_XARRAY,
ITER_DISCARD,
};
struct iov_iter {
/*
* Bit 0 is the read/write bit, set if we're writing.
* Bit 1 is the BVEC_FLAG_NO_REF bit, set if type is a bvec and
* the caller isn't expecting to drop a page reference when done.
*/
unsigned int type;
u8 iter_type;
bool data_source;
size_t iov_offset;
size_t count;
union {
@ -55,7 +51,7 @@ struct iov_iter {
static inline enum iter_type iov_iter_type(const struct iov_iter *i)
{
return i->type & ~(READ | WRITE);
return i->iter_type;
}
static inline bool iter_is_iovec(const struct iov_iter *i)
@ -90,7 +86,7 @@ static inline bool iov_iter_is_xarray(const struct iov_iter *i)
static inline unsigned char iov_iter_rw(const struct iov_iter *i)
{
return i->type & (READ | WRITE);
return i->data_source ? WRITE : READ;
}
/*