iov_iter_get_pages(): sanity-check arguments

zero maxpages is bogus, but best treated as "just return 0";
NULL pages, OTOH, should be treated as a hard bug.

get rid of now completely useless checks in xarray_get_pages{,_alloc}().

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index e14749711e342f0286f160c7f914de0a800bf717..7d3158d1f8ea9b6ddf93f55aca4964c40894c3ff 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1368,9 +1368,6 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i,
        size_t size = maxsize;
        loff_t pos;
 
-       if (!size || !maxpages)
-               return 0;
-
        pos = i->xarray_start + i->iov_offset;
        index = pos >> PAGE_SHIFT;
        offset = pos & ~PAGE_MASK;
@@ -1440,10 +1437,11 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
 
        if (maxsize > i->count)
                maxsize = i->count;
-       if (!maxsize)
+       if (!maxsize || !maxpages)
                return 0;
        if (maxsize > MAX_RW_COUNT)
                maxsize = MAX_RW_COUNT;
+       BUG_ON(!pages);
 
        if (likely(user_backed_iter(i))) {
                unsigned int gup_flags = 0;
@@ -1522,9 +1520,6 @@ static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
        size_t size = maxsize;
        loff_t pos;
 
-       if (!size)
-               return 0;
-
        pos = i->xarray_start + i->iov_offset;
        index = pos >> PAGE_SHIFT;
        offset = pos & ~PAGE_MASK;