Commit 66531c65 authored by Al Viro's avatar Al Viro
Browse files

iov_iter_npages(): don't bother with iterate_all_kinds() 



note that in bvec case pages can be compound ones - we can't just assume
that each segment is covered by one (sub)page

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 3d671ca6

lib/iov_iter.c

+54 −34
Original line number Diff line number Diff line
@@ -1864,19 +1864,56 @@ size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp, 
}

EXPORT_SYMBOL(hash_and_copy_to_iter);



int iov_iter_npages(const struct iov_iter *i, int maxpages)

static int iov_npages(const struct iov_iter *i, int maxpages)

{

	size_t size = i->count;

	size_t skip = i->iov_offset, size = i->count;

	const struct iovec *p;

	int npages = 0;



	if (!size)

		return 0;

	if (unlikely(iov_iter_is_discard(i)))

		return 0;

	for (p = i->iov; size; skip = 0, p++) {

		unsigned offs = offset_in_page(p->iov_base + skip);

		size_t len = min(p->iov_len - skip, size);



	if (unlikely(iov_iter_is_pipe(i))) {

		struct pipe_inode_info *pipe = i->pipe;

		if (len) {

			size -= len;

			npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);

			if (unlikely(npages > maxpages))

				return maxpages;

		}

	}

	return npages;

}



static int bvec_npages(const struct iov_iter *i, int maxpages)

{

	size_t skip = i->iov_offset, size = i->count;

	const struct bio_vec *p;

	int npages = 0;



	for (p = i->bvec; size; skip = 0, p++) {

		unsigned offs = (p->bv_offset + skip) % PAGE_SIZE;

		size_t len = min(p->bv_len - skip, size);



		size -= len;

		npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);

		if (unlikely(npages > maxpages))

			return maxpages;

	}

	return npages;

}



int iov_iter_npages(const struct iov_iter *i, int maxpages)

{

	if (unlikely(!i->count))

		return 0;

	/* iovec and kvec have identical layouts */

	if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))

		return iov_npages(i, 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))
@@ -1884,11 +1921,13 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages) 


		data_start(i, &iter_head, &off);

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

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

		if (npages >= maxpages)

			return maxpages;

	} else if (unlikely(iov_iter_is_xarray(i))) {

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

		return min(npages, maxpages);

	}

	if (iov_iter_is_xarray(i)) {

		size_t size = i->count;

		unsigned offset;

		int npages;



		offset = (i->xarray_start + i->iov_offset) & ~PAGE_MASK;
@@ -1900,28 +1939,9 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages) 
			if (size)

				npages++;

		}

		if (npages >= maxpages)

			return maxpages;

	} else iterate_all_kinds(i, size, v, ({

		unsigned long p = (unsigned long)v.iov_base;

		npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)

			- p / PAGE_SIZE;

		if (npages >= maxpages)

			return maxpages;

	0;}),({

		npages++;

		if (npages >= maxpages)

			return maxpages;

	}),({

		unsigned long p = (unsigned long)v.iov_base;

		npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)

			- p / PAGE_SIZE;

		if (npages >= maxpages)

			return maxpages;

	}),

	0

	)

	return npages;

		return min(npages, maxpages);

	}

	return 0;

}

EXPORT_SYMBOL(iov_iter_npages);