The patch titled
radix-tree: cleanup radix_tree_deref_slot() and _lookup_slot() comments
has been removed from the -mm tree. Its filename is
radix-tree-cleanup-radix_tree_deref_slot-and.patch
This patch was dropped because it was folded into radix-tree-rcu-lockless-readside.patch
------------------------------------------------------
Subject: radix-tree: cleanup radix_tree_deref_slot() and _lookup_slot() comments
From: Lee Schermerhorn <Lee.Schermerhorn@xxxxxx>
radix_tree_deref_slot() was actually dereferencing the pointer in the
assignment to the local variable 'slot' and then rcu_dereference()ing the
results of an expression [return value of an inline function].
Because we must hold the tree locked across lookup_slot() and
_deref_slot(), we don't need the rcu_dereference() at all.
Added comments specifying required locking for _lookup_slot() and
_deref_slot().
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/linux/radix-tree.h | 9 +++++++--
lib/radix-tree.c | 5 ++++-
2 files changed, 11 insertions(+), 3 deletions(-)
diff -puN include/linux/radix-tree.h~radix-tree-cleanup-radix_tree_deref_slot-and include/linux/radix-tree.h
--- a/include/linux/radix-tree.h~radix-tree-cleanup-radix_tree_deref_slot-and
+++ a/include/linux/radix-tree.h
@@ -122,12 +122,17 @@ do { \
/**
* radix_tree_deref_slot - dereference a slot
* @pslot: pointer to slot, returned by radix_tree_lookup_slot
- * @returns: item that was stored in that slot.
+ * @returns: item that was stored in that slot with any direct pointer flag
+ * removed.
+ *
+ * For use with radix_tree_lookup_slot(). Caller must hold tree at least read
+ * locked across slot lookup and dereference. More likely, will be used with
+ * radix_tree_replace_slot(), as well, so caller will hold tree write locked.
*/
static inline void *radix_tree_deref_slot(void *pslot)
{
void *slot = *(void **)pslot;
- return rcu_dereference(radix_tree_direct_to_ptr(slot));
+ return radix_tree_direct_to_ptr(slot);
}
/**
* radix_tree_replace_slot - replace item in a slot
diff -puN lib/radix-tree.c~radix-tree-cleanup-radix_tree_deref_slot-and lib/radix-tree.c
--- a/lib/radix-tree.c~radix-tree-cleanup-radix_tree_deref_slot-and
+++ a/lib/radix-tree.c
@@ -335,7 +335,10 @@ EXPORT_SYMBOL(radix_tree_insert);
* @root. This is useful for update-if-exists operations.
*
* This function cannot be called under rcu_read_lock, it must be
- * excluded from writers, as must the returned slot.
+ * excluded from writers, as must the returned slot for subsequent
+ * use by radix_tree_deref_slot() and radix_tree_replace slot.
+ * Caller must hold tree write locked across slot lookup and
+ * replace.
*/
void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
{
_
Patches currently in -mm which might be from Lee.Schermerhorn@xxxxxx are
radix-tree-rcu-lockless-readside.patch
radix-tree-cleanup-radix_tree_deref_slot-and.patch
cleanup-radix_tree_derefreplace_slot-calling-conventions.patch
cleanup-radix_tree_derefreplace_slot-calling-conventions-warning-fixes.patch
mempolicies-fix-policy_zone-check.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
