unify pipe_get_pages() and pipe_get_pages_alloc()

	The differences between those two are
* pipe_get_pages() gets a non-NULL struct page ** value pointing to
preallocated array + array size.
* pipe_get_pages_alloc() gets an address of struct page ** variable that
contains NULL, allocates the array and (on success) stores its address in
that variable.

	Not hard to combine - always pass struct page ***, have
the previous pipe_get_pages_alloc() caller pass ~0U as cap for
array size.

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 7d3158d1f8ea9b6ddf93f55aca4964c40894c3ff..916c628f80a075cc8f5ffda183d4c43930bbab6e 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1284,6 +1284,11 @@ 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)
+{
+       return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
+}
+
 static inline ssize_t __pipe_get_pages(struct iov_iter *i,
                                size_t maxsize,
                                struct page **pages,
@@ -1317,10 +1322,11 @@ static inline ssize_t __pipe_get_pages(struct iov_iter *i,
 }
 
 static ssize_t pipe_get_pages(struct iov_iter *i,
-                  struct page **pages, size_t maxsize, unsigned maxpages,
+                  struct page ***pages, size_t maxsize, unsigned maxpages,
                   size_t *start)
 {
        unsigned int npages, off;
+       struct page **p;
        size_t capacity;
 
        if (!sanity(i))
@@ -1328,8 +1334,15 @@ static ssize_t pipe_get_pages(struct iov_iter *i,
 
        *start = off = pipe_npages(i, &npages);
        capacity = min(npages, maxpages) * PAGE_SIZE - off;
+       maxsize = min(maxsize, capacity);
+       p = *pages;
+       if (!p) {
+               *pages = p = get_pages_array(DIV_ROUND_UP(maxsize + off, PAGE_SIZE));
+               if (!p)
+                       return -ENOMEM;
+       }
 
-       return __pipe_get_pages(i, min(maxsize, capacity), pages, off);
+       return __pipe_get_pages(i, maxsize, p, off);
 }
 
 static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
@@ -1475,41 +1488,13 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
                return min_t(size_t, maxsize, n * PAGE_SIZE - *start);
        }
        if (iov_iter_is_pipe(i))
-               return pipe_get_pages(i, pages, maxsize, maxpages, start);
+               return pipe_get_pages(i, &pages, maxsize, maxpages, start);
        if (iov_iter_is_xarray(i))
                return iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
        return -EFAULT;
 }
 EXPORT_SYMBOL(iov_iter_get_pages);
 
-static struct page **get_pages_array(size_t n)
-{
-       return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
-}
-
-static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
-                  struct page ***pages, size_t maxsize,
-                  size_t *start)
-{
-       struct page **p;
-       unsigned int npages, off;
-       ssize_t n;
-
-       if (!sanity(i))
-               return -EFAULT;
-
-       *start = off = pipe_npages(i, &npages);
-       n = npages * PAGE_SIZE - off;
-       if (maxsize > n)
-               maxsize = n;
-       else
-               npages = DIV_ROUND_UP(maxsize + off, PAGE_SIZE);
-       *pages = p = get_pages_array(npages);
-       if (!p)
-               return -ENOMEM;
-       return __pipe_get_pages(i, maxsize, p, off);
-}
-
 static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
                                           struct page ***pages, size_t maxsize,
                                           size_t *_start_offset)
@@ -1593,7 +1578,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
                return min_t(size_t, maxsize, n * PAGE_SIZE - *start);
        }
        if (iov_iter_is_pipe(i))
-               return pipe_get_pages_alloc(i, pages, maxsize, start);
+               return pipe_get_pages(i, pages, maxsize, ~0U, start);
        if (iov_iter_is_xarray(i))
                return iter_xarray_get_pages_alloc(i, pages, maxsize, start);
        return -EFAULT;