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
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(a)linux.intel.com>
Reviewed-by: Johannes Thumshirn <jthumshirn(a)suse.de>
Johannes Thumshirn Storage
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