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mm: clarify the radix_tree exceptional cases

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Make the radix_tree exceptional cases, mostly in filemap.c, clearer.

It's hard to devise a suitable snappy name that illuminates the use by
shmem/tmpfs for swap, while keeping filemap/pagecache/radix_tree
generality.  And akpm points out that /* radix_tree_deref_retry(page) */
comments look like calls that have been commented out for unknown
reason.

Skirt the naming difficulty by rearranging these blocks to handle the
transient radix_tree_deref_retry(page) case first; then just explain the
remaining shmem/tmpfs swap case in a comment.

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins
2011-08-03 16:21:28 -07:00
committed by Linus Torvalds
parent e504f3fdd6
commit 8079b1c859
3 changed files with 53 additions and 26 deletions
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12
mm/shmem.c
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@@ -332,10 +332,14 @@ repeat:
if (unlikely(!page))
continue;
if (radix_tree_exception(page)) {
if (radix_tree_exceptional_entry(page))
goto export;
/* radix_tree_deref_retry(page) */
goto restart;
if (radix_tree_deref_retry(page))
goto restart;
/*
* Otherwise, we must be storing a swap entry
* here as an exceptional entry: so return it
* without attempting to raise page count.
*/
goto export;
}
if (!page_cache_get_speculative(page))
goto repeat;