From: Ross Zwisler Date: Tue, 2 Aug 2016 21:04:19 +0000 (-0700) Subject: radix-tree: fix comment about "exceptional" bits X-Git-Tag: v4.8-rc1~52^2~65 X-Git-Url: http://git.cascardo.info/?a=commitdiff_plain;h=a23216a2f1f8a30a3b6588c743681651e4a6aa94;p=cascardo%2Flinux.git radix-tree: fix comment about "exceptional" bits The bottom two bits of radix tree entries are reserved for special use by the radix tree code itself. A comment detailing their usage was added by commit 3bcadd6fa6c4 ("radix-tree: free up the bottom bit of exceptional entries for reuse") This comment states that if the bottom two bits are '11', this means that this is a locked exceptional entry. It turns out that this bit combination was never actually used. Radix tree locking for DAX was indeed implemented, but it actually used the third LSB: /* We use lowest available exceptional entry bit for locking */ #define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT) This locking code was also made specific to the DAX code instead of being generally implemented in radix-tree.h. So, fix the comment. Link: http://lkml.kernel.org/r/1468997731-2155-1-git-send-email-ross.zwisler@linux.intel.com Signed-off-by: Ross Zwisler Reviewed-by: Johannes Thumshirn Cc: Dave Chinner Cc: Jan Kara Cc: Konstantin Khlebnikov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index cbfee507c839..4c45105dece3 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -35,7 +35,7 @@ * 00 - data pointer * 01 - internal entry * 10 - exceptional entry - * 11 - locked exceptional entry + * 11 - this bit combination is currently unused/reserved * * The internal entry may be a pointer to the next level in the tree, a * sibling entry, or an indicator that the entry in this slot has been moved