iov_iter: replace iov_iter_copy_from_user_atomic() with iterator-advancing variant
Replacement is called copy_page_from_iter_atomic(); unlike the old primitive the
callers do *not* need to do iov_iter_advance() after it. In case when they end
up consuming less than they'd been given they need to do iov_iter_revert() on
everything they had not consumed. That, however, needs to be done only on slow
paths.
All in-tree callers converted. And that kills the last user of iterate_all_kinds()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 864c08d..78cb8f9 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -398,7 +398,7 @@ static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
/*
* Copy data from userspace to the current page
*/
- copied = iov_iter_copy_from_user_atomic(page, i, offset, count);
+ copied = copy_page_from_iter_atomic(page, offset, count, i);
/* Flush processor's dcache for this page */
flush_dcache_page(page);
@@ -412,20 +412,19 @@ static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
* The rest of the btrfs_file_write code will fall
* back to page at a time copies after we return 0.
*/
- if (!PageUptodate(page) && copied < count)
- copied = 0;
+ if (unlikely(copied < count)) {
+ if (!PageUptodate(page)) {
+ iov_iter_revert(i, copied);
+ copied = 0;
+ }
+ if (!copied)
+ break;
+ }
- iov_iter_advance(i, copied);
write_bytes -= copied;
total_copied += copied;
-
- /* Return to btrfs_file_write_iter to fault page */
- if (unlikely(copied == 0))
- break;
-
- if (copied < PAGE_SIZE - offset) {
- offset += copied;
- } else {
+ offset += copied;
+ if (offset == PAGE_SIZE) {
pg++;
offset = 0;
}