mm: cleanup add_to_page_cache_locked()

mm: cleanup add_to_page_cache_locked()

Make add_to_page_cache_locked() cleaner:

 - unindent most code of the function by inverting one condition;
 - streamline code no-error path;
 - move insert error path outside normal code path;
 - call radix_tree_preload_end() earlier;

No functional changes.

Signed-off-by: Kirill A. Shutemov <[email protected]>
Acked-by: Dave Hansen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Wu Fengguang <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Hillf Danton <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>