Commit 12d426ab authored by Al Viro's avatar Al Viro
Browse files

ITER_PIPE: fold data_start() and pipe_space_for_user() together 



All their callers are next to each other; all of them
want the total amount of pages and, possibly, the
offset in the partial final buffer.

Combine into a new helper (pipe_npages()), fix the
bogosity in pipe_space_for_user(), while we are at it.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 10f525a8

include/linux/pipe_fs_i.h

+0 −20
Original line number Diff line number Diff line
@@ -156,26 +156,6 @@ static inline bool pipe_full(unsigned int head, unsigned int tail, 
	return pipe_occupancy(head, tail) >= limit;

}



/**

 * pipe_space_for_user - Return number of slots available to userspace

 * @head: The pipe ring head pointer

 * @tail: The pipe ring tail pointer

 * @pipe: The pipe info structure

 */

static inline unsigned int pipe_space_for_user(unsigned int head, unsigned int tail,

					       struct pipe_inode_info *pipe)

{

	unsigned int p_occupancy, p_space;



	p_occupancy = pipe_occupancy(head, tail);

	if (p_occupancy >= pipe->max_usage)

		return 0;

	p_space = pipe->ring_size - p_occupancy;

	if (p_space > pipe->max_usage)

		p_space = pipe->max_usage;

	return p_space;

}



/**

 * pipe_buf_get - get a reference to a pipe_buffer

 * @pipe:	the pipe that the buffer belongs to

lib/iov_iter.c

+19 −25
Original line number Diff line number Diff line
@@ -436,18 +436,20 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction, 
}

EXPORT_SYMBOL(iov_iter_init);



static inline void data_start(const struct iov_iter *i,

			      unsigned int *iter_headp, size_t *offp)

// returns the offset in partial buffer (if any)

static inline unsigned int pipe_npages(const struct iov_iter *i, int *npages)

{

	struct pipe_inode_info *pipe = i->pipe;

	int used = pipe->head - pipe->tail;

	int off = i->last_offset;



	*npages = max((int)pipe->max_usage - used, 0);



	if (off > 0 && off < PAGE_SIZE) { // anon and not full

		*iter_headp = i->pipe->head - 1;

		*offp = off;

	} else {

		*iter_headp = i->pipe->head;

		*offp = 0;

		(*npages)++;

		return off;

	}

	return 0;

}



static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
@@ -1318,18 +1320,16 @@ static ssize_t pipe_get_pages(struct iov_iter *i, 
		   struct page **pages, size_t maxsize, unsigned maxpages,

		   size_t *start)

{

	unsigned int iter_head, npages;

	unsigned int npages, off;

	size_t capacity;



	if (!sanity(i))

		return -EFAULT;



	data_start(i, &iter_head, start);

	/* Amount of free space: some of this one + all after this one */

	npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);

	capacity = min(npages, maxpages) * PAGE_SIZE - *start;

	*start = off = pipe_npages(i, &npages);

	capacity = min(npages, maxpages) * PAGE_SIZE - off;



	return __pipe_get_pages(i, min(maxsize, capacity), pages, *start);

	return __pipe_get_pages(i, min(maxsize, capacity), pages, off);

}



static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
@@ -1494,24 +1494,22 @@ static ssize_t pipe_get_pages_alloc(struct iov_iter *i, 
		   size_t *start)

{

	struct page **p;

	unsigned int iter_head, npages;

	unsigned int npages, off;

	ssize_t n;



	if (!sanity(i))

		return -EFAULT;



	data_start(i, &iter_head, start);

	/* Amount of free space: some of this one + all after this one */

	npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);

	n = npages * PAGE_SIZE - *start;

	*start = off = pipe_npages(i, &npages);

	n = npages * PAGE_SIZE - off;

	if (maxsize > n)

		maxsize = n;

	else

		npages = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);

		npages = DIV_ROUND_UP(maxsize + off, PAGE_SIZE);

	p = get_pages_array(npages);

	if (!p)

		return -ENOMEM;

	n = __pipe_get_pages(i, maxsize, p, *start);

	n = __pipe_get_pages(i, maxsize, p, off);

	if (n > 0)

		*pages = p;

	else
@@ -1739,16 +1737,12 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages) 
	if (iov_iter_is_bvec(i))

		return bvec_npages(i, maxpages);

	if (iov_iter_is_pipe(i)) {

		unsigned int iter_head;

		int npages;

		size_t off;



		if (!sanity(i))

			return 0;



		data_start(i, &iter_head, &off);

		/* some of this one + all after this one */

		npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);

		pipe_npages(i, &npages);

		return min(npages, maxpages);

	}

	if (iov_iter_is_xarray(i)) {