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>

1 files changed, 11 insertions, 12 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 864c08d08a35..78cb8f9eaa6b 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;
 		}