[PATCH 12/31] iov_iter_get_pages_alloc(): lift freeing pages array on failure exits into wrapper

[Al Viro <viro@xxxxxxxxxxxxxxxxxx>]

Incidentally, ITER_XARRAY did *not* free the sucker in case when
iter_xarray_populate_pages() returned NULL...

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
 lib/iov_iter.c | 51 +++++++++++++++++++++++++++++---------------------
 1 file changed, 30 insertions(+), 21 deletions(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 2d4176a2a1b5..f5e14535f6bb 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1425,15 +1425,10 @@ static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
 		maxsize = n;
 	else
 		npages = DIV_ROUND_UP(maxsize + off, PAGE_SIZE);
-	p = get_pages_array(npages);
+	*pages = p = get_pages_array(npages);
 	if (!p)
 		return -ENOMEM;
-	n = __pipe_get_pages(i, maxsize, p, off);
-	if (n > 0)
-		*pages = p;
-	else
-		kvfree(p);
-	return n;
+	return __pipe_get_pages(i, maxsize, p, off);
 }
 
 static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
@@ -1463,10 +1458,9 @@ static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
 			count++;
 	}
 
-	p = get_pages_array(count);
+	*pages = p = get_pages_array(count);
 	if (!p)
 		return -ENOMEM;
-	*pages = p;
 
 	nr = iter_xarray_populate_pages(p, i->xarray, index, count);
 	if (nr == 0)
@@ -1475,7 +1469,7 @@ static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
 	return min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
 }
 
-ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
+static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
 		   struct page ***pages, size_t maxsize,
 		   size_t *start)
 {
@@ -1483,10 +1477,6 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 	size_t len;
 	int n, res;
 
-	if (maxsize > i->count)
-		maxsize = i->count;
-	if (!maxsize)
-		return 0;
 	if (maxsize > LONG_MAX)
 		maxsize = LONG_MAX;
 
@@ -1501,17 +1491,15 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 
 		addr = first_iovec_segment(i, &len, start, maxsize, ~0U);
 		n = DIV_ROUND_UP(len, PAGE_SIZE);
-		p = get_pages_array(n);
+		*pages = p = get_pages_array(n);
 		if (!p)
 			return -ENOMEM;
 		res = get_user_pages_fast(addr, n, gup_flags, p);
-		if (unlikely(res <= 0)) {
-			kvfree(p);
-			*pages = NULL;
+		if (unlikely(res <= 0))
 			return res;
-		}
-		*pages = p;
-		return (res == n ? len : res * PAGE_SIZE) - *start;
+		if (res < n)
+			len = res * PAGE_SIZE;
+		return len - *start;
 	}
 	if (iov_iter_is_bvec(i)) {
 		struct page *page;
@@ -1531,6 +1519,27 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 		return iter_xarray_get_pages_alloc(i, pages, maxsize, start);
 	return -EFAULT;
 }
+
+ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
+		   struct page ***pages, size_t maxsize,
+		   size_t *start)
+{
+	size_t len;
+
+	*pages = NULL;
+
+	if (maxsize > i->count)
+		maxsize = i->count;
+	if (!maxsize)
+		return 0;
+
+	len = __iov_iter_get_pages_alloc(i, pages, maxsize, start);
+	if (len <= 0) {
+		kvfree(*pages);
+		*pages = NULL;
+	}
+	return len;
+}
 EXPORT_SYMBOL(iov_iter_get_pages_alloc);
 
 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
-- 
2.30.2