Commit 3cf42da3 authored by Al Viro's avatar Al Viro
Browse files

iov_iter: saner helper for page array allocation 



All call sites of get_pages_array() are essenitally identical now.
Replace with common helper...

Returns number of slots available in resulting array or 0 on OOM;
it's up to the caller to make sure it doesn't ask to zero-entry
array (i.e. neither maxpages nor size are allowed to be zero).

Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 85200084

lib/iov_iter.c

+32 −45
Original line number Diff line number Diff line
@@ -1284,9 +1284,20 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i) 
}

EXPORT_SYMBOL(iov_iter_gap_alignment);



static struct page **get_pages_array(size_t n)

static int want_pages_array(struct page ***res, size_t size,

			    size_t start, unsigned int maxpages)

{

	return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);

	unsigned int count = DIV_ROUND_UP(size + start, PAGE_SIZE);



	if (count > maxpages)

		count = maxpages;

	WARN_ON(!count);	// caller should've prevented that

	if (!*res) {

		*res = kvmalloc_array(count, sizeof(struct page *), GFP_KERNEL);

		if (!*res)

			return 0;

	}

	return count;

}



static ssize_t pipe_get_pages(struct iov_iter *i,
@@ -1294,27 +1305,20 @@ static ssize_t pipe_get_pages(struct iov_iter *i, 
		   size_t *start)

{

	struct pipe_inode_info *pipe = i->pipe;

	unsigned int npages, off;

	unsigned int npages, off, count;

	struct page **p;

	ssize_t left;

	int count;



	if (!sanity(i))

		return -EFAULT;



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

	count = DIV_ROUND_UP(maxsize + off, PAGE_SIZE);

	if (count > npages)

		count = npages;

	if (count > maxpages)

		count = maxpages;

	p = *pages;

	if (!p) {

		*pages = p = get_pages_array(count);

		if (!p)

	if (!npages)

		return -EFAULT;

	count = want_pages_array(pages, maxsize, off, min(npages, maxpages));

	if (!count)

		return -ENOMEM;

	}



	p = *pages;

	left = maxsize;

	npages = 0;

	if (off) {
@@ -1377,9 +1381,8 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i, 
				     struct page ***pages, size_t maxsize,

				     unsigned maxpages, size_t *_start_offset)

{

	unsigned nr, offset;

	pgoff_t index, count;

	size_t size = maxsize;

	unsigned nr, offset, count;

	pgoff_t index;

	loff_t pos;



	pos = i->xarray_start + i->iov_offset;
@@ -1387,16 +1390,9 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i, 
	offset = pos & ~PAGE_MASK;

	*_start_offset = offset;



	count = DIV_ROUND_UP(size + offset, PAGE_SIZE);

	if (count > maxpages)

		count = maxpages;



	if (!*pages) {

		*pages = get_pages_array(count);

		if (!*pages)

	count = want_pages_array(pages, maxsize, offset, maxpages);

	if (!count)

		return -ENOMEM;

	}



	nr = iter_xarray_populate_pages(*pages, i->xarray, index, count);

	if (nr == 0)

		return 0;
@@ -1445,7 +1441,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, 
		   struct page ***pages, size_t maxsize,

		   unsigned int maxpages, size_t *start)

{

	int n, res;

	unsigned int n;



	if (maxsize > i->count)

		maxsize = i->count;
@@ -1457,6 +1453,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, 
	if (likely(user_backed_iter(i))) {

		unsigned int gup_flags = 0;

		unsigned long addr;

		int res;



		if (iov_iter_rw(i) != WRITE)

			gup_flags |= FOLL_WRITE;
@@ -1466,14 +1463,9 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, 
		addr = first_iovec_segment(i, &maxsize);

		*start = addr % PAGE_SIZE;

		addr &= PAGE_MASK;

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

		if (n > maxpages)

			n = maxpages;

		if (!*pages) {

			*pages = get_pages_array(n);

			if (!*pages)

		n = want_pages_array(pages, maxsize, *start, maxpages);

		if (!n)

			return -ENOMEM;

		}

		res = get_user_pages_fast(addr, n, gup_flags, *pages);

		if (unlikely(res <= 0))

			return res;
@@ -1484,15 +1476,10 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, 
		struct page *page;



		page = first_bvec_segment(i, &maxsize, start);

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

		if (n > maxpages)

			n = maxpages;

		p = *pages;

		if (!p) {

			*pages = p = get_pages_array(n);

			if (!p)

		n = want_pages_array(pages, maxsize, *start, maxpages);

		if (!n)

			return -ENOMEM;

		}

		p = *pages;

		for (int k = 0; k < n; k++)

			get_page(*p++ = page++);

		return min_t(size_t, maxsize, n * PAGE_SIZE - *start);