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Date: Sun, 6 Jun 2021 19:10:26 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
David Sterba <dsterba@...e.com>,
Miklos Szeredi <miklos@...redi.hu>,
Anton Altaparmakov <anton@...era.com>,
David Howells <dhowells@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Pavel Begunkov <asml.silence@...il.com>
Subject: [RFC PATCH 12/37] iov_iter: separate direction from flavour
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@...iv.linux.org.uk>
---
include/linux/uio.h | 24 ++++++--------
lib/iov_iter.c | 92 +++++++++++++++++++++++++++++++++--------------------
2 files changed, 67 insertions(+), 49 deletions(-)
diff --git a/include/linux/uio.h b/include/linux/uio.h
index c697c23138b5..56b6ff235281 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -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;
}
/*
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index e6c5834da32d..5a02c94a51ab 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -489,19 +489,26 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
size_t count)
{
WARN_ON(direction & ~(READ | WRITE));
- direction &= READ | WRITE;
/* It will get better. Eventually... */
- if (uaccess_kernel()) {
- i->type = ITER_KVEC | direction;
- i->kvec = (struct kvec *)iov;
- } else {
- i->type = ITER_IOVEC | direction;
- i->iov = iov;
- }
- i->nr_segs = nr_segs;
- i->iov_offset = 0;
- i->count = count;
+ if (uaccess_kernel())
+ *i = (struct iov_iter) {
+ .iter_type = ITER_KVEC,
+ .data_source = direction,
+ .kvec = (struct kvec *)iov,
+ .nr_segs = nr_segs,
+ .iov_offset = 0,
+ .count = count
+ };
+ else
+ *i = (struct iov_iter) {
+ .iter_type = ITER_IOVEC,
+ .data_source = direction,
+ .iov = iov,
+ .nr_segs = nr_segs,
+ .iov_offset = 0,
+ .count = count
+ };
}
EXPORT_SYMBOL(iov_iter_init);
@@ -1218,11 +1225,14 @@ void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
size_t count)
{
WARN_ON(direction & ~(READ | WRITE));
- i->type = ITER_KVEC | (direction & (READ | WRITE));
- i->kvec = kvec;
- i->nr_segs = nr_segs;
- i->iov_offset = 0;
- i->count = count;
+ *i = (struct iov_iter){
+ .iter_type = ITER_KVEC,
+ .data_source = direction,
+ .kvec = kvec,
+ .nr_segs = nr_segs,
+ .iov_offset = 0,
+ .count = count
+ };
}
EXPORT_SYMBOL(iov_iter_kvec);
@@ -1231,11 +1241,14 @@ void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
size_t count)
{
WARN_ON(direction & ~(READ | WRITE));
- i->type = ITER_BVEC | (direction & (READ | WRITE));
- i->bvec = bvec;
- i->nr_segs = nr_segs;
- i->iov_offset = 0;
- i->count = count;
+ *i = (struct iov_iter){
+ .iter_type = ITER_BVEC,
+ .data_source = direction,
+ .bvec = bvec,
+ .nr_segs = nr_segs,
+ .iov_offset = 0,
+ .count = count
+ };
}
EXPORT_SYMBOL(iov_iter_bvec);
@@ -1245,12 +1258,15 @@ void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
{
BUG_ON(direction != READ);
WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));
- i->type = ITER_PIPE | READ;
- i->pipe = pipe;
- i->head = pipe->head;
- i->iov_offset = 0;
- i->count = count;
- i->start_head = i->head;
+ *i = (struct iov_iter){
+ .iter_type = ITER_PIPE,
+ .data_source = false,
+ .pipe = pipe,
+ .head = pipe->head,
+ .start_head = pipe->head,
+ .iov_offset = 0,
+ .count = count
+ };
}
EXPORT_SYMBOL(iov_iter_pipe);
@@ -1271,11 +1287,14 @@ void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
struct xarray *xarray, loff_t start, size_t count)
{
BUG_ON(direction & ~1);
- i->type = ITER_XARRAY | (direction & (READ | WRITE));
- i->xarray = xarray;
- i->xarray_start = start;
- i->count = count;
- i->iov_offset = 0;
+ *i = (struct iov_iter) {
+ .iter_type = ITER_XARRAY,
+ .data_source = direction,
+ .xarray = xarray,
+ .xarray_start = start,
+ .count = count,
+ .iov_offset = 0
+ };
}
EXPORT_SYMBOL(iov_iter_xarray);
@@ -1291,9 +1310,12 @@ EXPORT_SYMBOL(iov_iter_xarray);
void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
{
BUG_ON(direction != READ);
- i->type = ITER_DISCARD | READ;
- i->count = count;
- i->iov_offset = 0;
+ *i = (struct iov_iter){
+ .iter_type = ITER_DISCARD,
+ .data_source = false,
+ .count = count,
+ .iov_offset = 0
+ };
}
EXPORT_SYMBOL(iov_iter_discard);
--
2.11.0
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