new helper: iov_iter_npages()
counts the pages covered by iov_iter, up to given limit.
do_block_direct_io() and fuse_iter_npages() switched to
it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index 45204cd..0b677f8 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -262,3 +262,30 @@
return (res == n ? len : res * PAGE_SIZE) - *start;
}
EXPORT_SYMBOL(iov_iter_get_pages);
+
+int iov_iter_npages(const struct iov_iter *i, int maxpages)
+{
+ size_t offset = i->iov_offset;
+ size_t size = i->count;
+ const struct iovec *iov = i->iov;
+ int npages = 0;
+ int n;
+
+ for (n = 0; size && n < i->nr_segs; n++, iov++) {
+ unsigned long addr = (unsigned long)iov->iov_base + offset;
+ size_t len = iov->iov_len - offset;
+ offset = 0;
+ if (unlikely(!len)) /* empty segment */
+ continue;
+ if (len > size)
+ len = size;
+ npages += (addr + len + PAGE_SIZE - 1) / PAGE_SIZE
+ - addr / PAGE_SIZE;
+ if (npages >= maxpages) /* don't bother going further */
+ return maxpages;
+ size -= len;
+ offset = 0;
+ }
+ return min(npages, maxpages);
+}
+EXPORT_SYMBOL(iov_iter_npages);
