lkml.org 
[lkml]   [2016]   [Jul]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] radix-tree: fix comment about "exceptional" bits
Date
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.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
include/linux/radix-tree.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index cb4b7e8..f0fb327 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
--
2.7.4
\
 
 \ /
  Last update: 2016-07-20 09:41    [W:0.030 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site