Messages in this thread Patch in this message | | | From | Ross Zwisler <> | Subject | [PATCH] radix-tree: fix comment about "exceptional" bits | Date | Wed, 20 Jul 2016 00:55:31 -0600 |
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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
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