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authorDavid Howells <dhowells@redhat.com>2018-10-20 00:57:56 +0100
committerDavid Howells <dhowells@redhat.com>2018-10-24 00:41:07 +0100
commitaa563d7bca6e882ec2bdae24603c8f016401a144 (patch)
tree874b10fc11da3178e4630f7a430e1b299d3b3806 /lib
parent00e23707442a75b404392cef1405ab4fd498de6b (diff)
downloadlinux-aa563d7bca6e882ec2bdae24603c8f016401a144.tar.gz
iov_iter: Separate type from direction and use accessor functions
In the iov_iter struct, separate the iterator type from the iterator direction and use accessor functions to access them in most places. Convert a bunch of places to use switch-statements to access them rather then chains of bitwise-AND statements. This makes it easier to add further iterator types. Also, this can be more efficient as to implement a switch of small contiguous integers, the compiler can use ~50% fewer compare instructions than it has to use bitwise-and instructions. Further, cease passing the iterator type into the iterator setup function. The iterator function can set that itself. Only the direction is required. Signed-off-by: David Howells <dhowells@redhat.com>
Diffstat (limited to 'lib')
-rw-r--r--lib/iov_iter.c28
1 files changed, 15 insertions, 13 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 42d39116a556..c42b928b15ef 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -428,17 +428,19 @@ int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
}
EXPORT_SYMBOL(iov_iter_fault_in_readable);
-void iov_iter_init(struct iov_iter *i, int direction,
+void iov_iter_init(struct iov_iter *i, unsigned int direction,
const struct iovec *iov, unsigned long nr_segs,
size_t count)
{
+ WARN_ON(direction & ~(READ | WRITE));
+ direction &= READ | WRITE;
+
/* It will get better. Eventually... */
if (uaccess_kernel()) {
- direction |= ITER_KVEC;
- i->type = direction;
+ i->type = ITER_KVEC | direction;
i->kvec = (struct kvec *)iov;
} else {
- i->type = direction;
+ i->type = ITER_IOVEC | direction;
i->iov = iov;
}
i->nr_segs = nr_segs;
@@ -1060,12 +1062,12 @@ size_t iov_iter_single_seg_count(const struct iov_iter *i)
}
EXPORT_SYMBOL(iov_iter_single_seg_count);
-void iov_iter_kvec(struct iov_iter *i, int direction,
+void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
const struct kvec *kvec, unsigned long nr_segs,
size_t count)
{
- BUG_ON(!(direction & ITER_KVEC));
- i->type = direction;
+ WARN_ON(direction & ~(READ | WRITE));
+ i->type = ITER_KVEC | (direction & (READ | WRITE));
i->kvec = kvec;
i->nr_segs = nr_segs;
i->iov_offset = 0;
@@ -1073,12 +1075,12 @@ void iov_iter_kvec(struct iov_iter *i, int direction,
}
EXPORT_SYMBOL(iov_iter_kvec);
-void iov_iter_bvec(struct iov_iter *i, int direction,
+void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
const struct bio_vec *bvec, unsigned long nr_segs,
size_t count)
{
- BUG_ON(!(direction & ITER_BVEC));
- i->type = direction;
+ WARN_ON(direction & ~(READ | WRITE));
+ i->type = ITER_BVEC | (direction & (READ | WRITE));
i->bvec = bvec;
i->nr_segs = nr_segs;
i->iov_offset = 0;
@@ -1086,13 +1088,13 @@ void iov_iter_bvec(struct iov_iter *i, int direction,
}
EXPORT_SYMBOL(iov_iter_bvec);
-void iov_iter_pipe(struct iov_iter *i, int direction,
+void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
struct pipe_inode_info *pipe,
size_t count)
{
- BUG_ON(direction != ITER_PIPE);
+ BUG_ON(direction != READ);
WARN_ON(pipe->nrbufs == pipe->buffers);
- i->type = direction;
+ i->type = ITER_PIPE | READ;
i->pipe = pipe;
i->idx = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
i->iov_offset = 0;