On Wed, Jul 20, 2016 at 12:55:31AM -0600, Ross Zwisler wrote:
> 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.zwis...@linux.intel.com>
Reviewed-by: Johannes Thumshirn <jthumsh...@suse.de>
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