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| author | Al Viro <viro@zeniv.linux.org.uk> | 2022-06-14 10:24:37 -0400 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2022-08-08 22:37:16 -0400 |
| commit | 2dcedb2a549a4d7430538213b1b28ef7271bc0aa (patch) | |
| tree | d6af7d3df8f6c016b030e119dda9ce915f421a2e /lib | |
| parent | 0d9649341363047be60a9ec7378d8985bdd0abba (diff) | |
| download | linux-2dcedb2a549a4d7430538213b1b28ef7271bc0aa.tar.bz2 | |
ITER_PIPE: helper for getting pipe buffer by index
pipe_buffer instances of a pipe are organized as a ring buffer,
with power-of-2 size. Indices are kept *not* reduced modulo ring
size, so the buffer refered to by index N is
pipe->bufs[N & (pipe->ring_size - 1)].
Ring size can change over the lifetime of a pipe, but not while
the pipe is locked. So for any iov_iter primitives it's a constant.
Original conversion of pipes to this layout went overboard trying
to microoptimize that - calculating pipe->ring_size - 1, storing
it in a local variable and using through the function. In some
cases it might be warranted, but most of the times it only
obfuscates what's going on in there.
Introduce a helper (pipe_buf(pipe, N)) that would encapsulate
that and use it in the obvious cases. More will follow...
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/iov_iter.c | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c index b3493d20536e..048026d5aa0d 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -183,13 +183,18 @@ static int copyin(void *to, const void __user *from, size_t n) return n; } +static inline struct pipe_buffer *pipe_buf(const struct pipe_inode_info *pipe, + unsigned int slot) +{ + return &pipe->bufs[slot & (pipe->ring_size - 1)]; +} + #ifdef PIPE_PARANOIA static bool sanity(const struct iov_iter *i) { struct pipe_inode_info *pipe = i->pipe; unsigned int p_head = pipe->head; unsigned int p_tail = pipe->tail; - unsigned int p_mask = pipe->ring_size - 1; unsigned int p_occupancy = pipe_occupancy(p_head, p_tail); unsigned int i_head = i->head; unsigned int idx; @@ -201,7 +206,7 @@ static bool sanity(const struct iov_iter *i) if (unlikely(i_head != p_head - 1)) goto Bad; // must be at the last buffer... - p = &pipe->bufs[i_head & p_mask]; + p = pipe_buf(pipe, i_head); if (unlikely(p->offset + p->len != i->iov_offset)) goto Bad; // ... at the end of segment } else { @@ -386,11 +391,10 @@ static inline bool allocated(struct pipe_buffer *buf) static inline void data_start(const struct iov_iter *i, unsigned int *iter_headp, size_t *offp) { - unsigned int p_mask = i->pipe->ring_size - 1; unsigned int iter_head = i->head; size_t off = i->iov_offset; - if (off && (!allocated(&i->pipe->bufs[iter_head & p_mask]) || + if (off && (!allocated(pipe_buf(i->pipe, iter_head)) || off == PAGE_SIZE)) { iter_head++; off = 0; @@ -1280,10 +1284,9 @@ unsigned long iov_iter_alignment(const struct iov_iter *i) return iov_iter_alignment_bvec(i); if (iov_iter_is_pipe(i)) { - unsigned int p_mask = i->pipe->ring_size - 1; size_t size = i->count; - if (size && i->iov_offset && allocated(&i->pipe->bufs[i->head & p_mask])) + if (size && i->iov_offset && allocated(pipe_buf(i->pipe, i->head))) return size | i->iov_offset; return size; } |