mm/swap.c: introduce put_[un]refcounted_compound_page helpers for splitting put_compound_page()

Currently, put_compound_page() carefully handles tricky cases to avoid
racing with compound page releasing or splitting, which makes it quite
lenthy (about 200+ lines) and needs deep tab indention, which makes it
quite hard to follow and maintain.

This patch and the next patch refactor this function.

Based on the code skeleton of put_compound_page:

put_compound_pge:
        if !PageTail(page)
        	put head page fastpath;
		return;

        /* else PageTail */
        page_head = compound_head(page)
        if !__compound_tail_refcounted(page_head)
		put head page optimal path; <---(1)
		return;
        else
		put head page slowpath; <--- (2)
                return;

This patch introduces two helpers, put_[un]refcounted_compound_page,
handling the code path (1) and code path (2), respectively.  They both are
tagged __always_inline, thus elmiating function call overhead, making them
operating the same way as before.

They are almost copied verbatim(except one place, a "goto out_put_single"
is expanded), with some comments rephrasing.

Signed-off-by: Jianyu Zhan <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Jiang Liu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions