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authorRoss Zwisler <ross.zwisler@linux.intel.com>2016-08-02 14:04:19 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-08-02 19:35:08 -0400
commita23216a2f1f8a30a3b6588c743681651e4a6aa94 (patch)
tree7f8ab6d1d79ef4e48d208faefc7485dd8ca84f75 /include
parenta9bfd3321713ecec86282dd2bec04212189f91f1 (diff)
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 <ross.zwisler@linux.intel.com> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/radix-tree.h2
1 files changed, 1 insertions, 1 deletions
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