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author | Cody P Schafer <cody@linux.vnet.ibm.com> | 2013-09-11 14:25:10 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-09-11 15:59:19 -0700 |
commit | 9dee5c51516d2c3fff22633c1272c5652e68075a (patch) | |
tree | b8d1811b0357a74c720008911e06559f772ce731 /include/linux/rbtree.h | |
parent | b4bc4a18a226f46fec4ef47f2df28ea209db8b5d (diff) | |
download | linux-stable-9dee5c51516d2c3fff22633c1272c5652e68075a.tar.gz linux-stable-9dee5c51516d2c3fff22633c1272c5652e68075a.tar.bz2 linux-stable-9dee5c51516d2c3fff22633c1272c5652e68075a.zip |
rbtree: add postorder iteration functions
Postorder iteration yields all of a node's children prior to yielding the
node itself, and this particular implementation also avoids examining the
leaf links in a node after that node has been yielded.
In what I expect will be its most common usage, postorder iteration allows
the deletion of every node in an rbtree without modifying the rbtree nodes
(no _requirement_ that they be nulled) while avoiding referencing child
nodes after they have been "deleted" (most commonly, freed).
I have only updated zswap to use this functionality at this point, but
numerous bits of code (most notably in the filesystem drivers) use a hand
rolled postorder iteration that NULLs child links as it traverses the
tree. Each of those instances could be replaced with this common
implementation.
1 & 2 add rbtree postorder iteration functions.
3 adds testing of the iteration to the rbtree runtime tests
4 allows building the rbtree runtime tests as builtins
5 updates zswap.
This patch:
Add postorder iteration functions for rbtree. These are useful for safely
freeing an entire rbtree without modifying the tree at all.
Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Reviewed-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: David Woodhouse <David.Woodhouse@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/rbtree.h')
-rw-r--r-- | include/linux/rbtree.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h index 0022c1bb1e26..c467151e9950 100644 --- a/include/linux/rbtree.h +++ b/include/linux/rbtree.h @@ -68,6 +68,10 @@ extern struct rb_node *rb_prev(const struct rb_node *); extern struct rb_node *rb_first(const struct rb_root *); extern struct rb_node *rb_last(const struct rb_root *); +/* Postorder iteration - always visit the parent after its children */ +extern struct rb_node *rb_first_postorder(const struct rb_root *); +extern struct rb_node *rb_next_postorder(const struct rb_node *); + /* Fast replacement of a single node without remove/rebalance/add/rebalance */ extern void rb_replace_node(struct rb_node *victim, struct rb_node *new, struct rb_root *root); |