iov_iter: Map the page later in copy_page_from_iter_atomic()

Remove a couple of calls to kunmap_atomic() in the rare error cases.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index e4dc809..db58af7 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -569,20 +569,20 @@ EXPORT_SYMBOL(iov_iter_zero);
 size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes,
                                  struct iov_iter *i)
 {
-       char *kaddr = kmap_atomic(page), *p = kaddr + offset;
-       if (!page_copy_sane(page, offset, bytes)) {
-               kunmap_atomic(kaddr);
+       char *p;
+
+       if (!page_copy_sane(page, offset, bytes))
                return 0;
-       }
-       if (WARN_ON_ONCE(!i->data_source)) {
-               kunmap_atomic(kaddr);
+       if (WARN_ON_ONCE(!i->data_source))
                return 0;
-       }
+
+       p = kmap_atomic(page) + offset;
        iterate_and_advance(i, bytes, base, len, off,
                copyin(p + off, base, len),
                memcpy_from_iter(i, p + off, base, len)
        )
-       kunmap_atomic(kaddr);
+       kunmap_atomic(p);
+
        return bytes;
 }
 EXPORT_SYMBOL(copy_page_from_iter_atomic);