unify the rest of iov_iter_get_pages()/iov_iter_get_pages_alloc() guts

same as for pipes and xarrays; after that iov_iter_get_pages() becomes
a wrapper for __iov_iter_get_pages_alloc().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 6904a1cc36f26413c35a590bb57ea87ec63e6b2e..8c6cdc1cf832be804b470c6bb07287e716df8dae 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1448,19 +1448,18 @@ static struct page *first_bvec_segment(const struct iov_iter *i,
        return page;
 }
 
-ssize_t iov_iter_get_pages(struct iov_iter *i,
-                  struct page **pages, size_t maxsize, unsigned maxpages,
-                  size_t *start)
+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;
 
        if (maxsize > i->count)
                maxsize = i->count;
-       if (!maxsize || !maxpages)
+       if (!maxsize)
                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;
@@ -1477,83 +1476,52 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
                n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
                if (n > maxpages)
                        n = maxpages;
-               res = get_user_pages_fast(addr, n, gup_flags, pages);
+               if (!*pages) {
+                       *pages = get_pages_array(n);
+                       if (!*pages)
+                               return -ENOMEM;
+               }
+               res = get_user_pages_fast(addr, n, gup_flags, *pages);
                if (unlikely(res <= 0))
                        return res;
                return min_t(size_t, maxsize, res * PAGE_SIZE - *start);
        }
        if (iov_iter_is_bvec(i)) {
+               struct page **p;
                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)
+                               return -ENOMEM;
+               }
                for (int k = 0; k < n; k++)
-                       get_page(*pages++ = page++);
+                       get_page(*p++ = page++);
                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 iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
        return -EFAULT;
 }
-EXPORT_SYMBOL(iov_iter_get_pages);
 
-static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
-                  struct page ***pages, size_t maxsize,
+ssize_t iov_iter_get_pages(struct iov_iter *i,
+                  struct page **pages, size_t maxsize, unsigned maxpages,
                   size_t *start)
 {
-       struct page **p;
-       int n, res;
-
-       if (maxsize > i->count)
-               maxsize = i->count;
-       if (!maxsize)
+       if (!maxpages)
                return 0;
-       if (maxsize > MAX_RW_COUNT)
-               maxsize = MAX_RW_COUNT;
-
-       if (likely(user_backed_iter(i))) {
-               unsigned int gup_flags = 0;
-               unsigned long addr;
-
-               if (iov_iter_rw(i) != WRITE)
-                       gup_flags |= FOLL_WRITE;
-               if (i->nofault)
-                       gup_flags |= FOLL_NOFAULT;
-
-               addr = first_iovec_segment(i, &maxsize);
-               *start = addr % PAGE_SIZE;
-               addr &= PAGE_MASK;
-               n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
-               *pages = p = get_pages_array(n);
-               if (!p)
-                       return -ENOMEM;
-               res = get_user_pages_fast(addr, n, gup_flags, p);
-               if (unlikely(res <= 0))
-                       return res;
-               return min_t(size_t, maxsize, res * PAGE_SIZE - *start);
-       }
-       if (iov_iter_is_bvec(i)) {
-               struct page *page;
+       BUG_ON(!pages);
 
-               page = first_bvec_segment(i, &maxsize, start);
-               n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
-               *pages = p = get_pages_array(n);
-               if (!p)
-                       return -ENOMEM;
-               for (int k = 0; k < n; k++)
-                       get_page(*p++ = page++);
-               return min_t(size_t, maxsize, n * PAGE_SIZE - *start);
-       }
-       if (iov_iter_is_pipe(i))
-               return pipe_get_pages(i, pages, maxsize, ~0U, start);
-       if (iov_iter_is_xarray(i))
-               return iter_xarray_get_pages(i, pages, maxsize, ~0U, start);
-       return -EFAULT;
+       return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start);
 }
+EXPORT_SYMBOL(iov_iter_get_pages);
 
 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
                   struct page ***pages, size_t maxsize,
@@ -1563,7 +1531,7 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 
        *pages = NULL;
 
-       len = __iov_iter_get_pages_alloc(i, pages, maxsize, start);
+       len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start);
        if (len <= 0) {
                kvfree(*pages);
                *pages = NULL;