diff options
| author | Ross Zwisler <ross.zwisler@linux.intel.com> | 2016-08-02 14:04:19 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-08-02 19:35:08 -0400 |
| commit | a23216a2f1f8a30a3b6588c743681651e4a6aa94 (patch) | |
| tree | 7f8ab6d1d79ef4e48d208faefc7485dd8ca84f75 /include | |
| parent | a9bfd3321713ecec86282dd2bec04212189f91f1 (diff) | |
| download | linux-a23216a2f1f8a30a3b6588c743681651e4a6aa94.tar.bz2 | |
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.h | 2 |
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 |