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Date: Sun, 12 Jan 2014 21:48:13 -0500
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: Theodore Ts'o <tytso@....edu>
Subject: [PATCH 5/5] libext2fs: optimize find_first_{zero,set}() for red-black tree based bitmaps
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
lib/ext2fs/blkmap64_rb.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 114 insertions(+)
diff --git a/lib/ext2fs/blkmap64_rb.c b/lib/ext2fs/blkmap64_rb.c
index 0e0a217..5be6a4c 100644
--- a/lib/ext2fs/blkmap64_rb.c
+++ b/lib/ext2fs/blkmap64_rb.c
@@ -809,6 +809,118 @@ static void rb_clear_bmap(ext2fs_generic_bitmap bitmap)
check_tree(&bp->root, __func__);
}
+static errcode_t rb_find_first_zero(ext2fs_generic_bitmap bitmap,
+ __u64 start, __u64 end, __u64 *out)
+{
+ struct rb_node *parent = NULL, **n;
+ struct rb_node *node, *next;
+ struct ext2fs_rb_private *bp;
+ struct bmap_rb_extent *ext;
+ int retval = 1;
+ __u64 b;
+
+ bp = (struct ext2fs_rb_private *) bitmap->private;
+ n = &bp->root.rb_node;
+ start -= bitmap->start;
+ end -= bitmap->start;
+
+ if (start > end)
+ return EINVAL;
+
+ if (EXT2FS_RB_EMPTY_ROOT(&bp->root))
+ return ENOENT;
+
+ while (*n) {
+ parent = *n;
+ ext = node_to_extent(parent);
+ if (start < ext->start) {
+ n = &(*n)->rb_left;
+ } else if (start >= (ext->start + ext->count)) {
+ n = &(*n)->rb_right;
+ } else if (ext->start + ext->count <= end) {
+ *out = ext->start + ext->count + bitmap->start;
+ return 0;
+ } else
+ return ENOENT;
+ }
+
+ node = parent;
+ ext = node_to_extent(node);
+ while (ext->start > start) {
+ node = ext2fs_rb_prev(node);
+ if (node == NULL) {
+ *out = start + bitmap->start;
+ return 0;
+ }
+ ext = node_to_extent(node);
+ }
+ while (1) {
+ __u64 ext_end = ext->start + ext->count;
+ if (ext_end >= start && ext_end <= end) {
+ *out = b + bitmap->start;
+ return 0;
+ }
+ if (ext_end > end)
+ return ENOENT;
+ node = ext2fs_rb_next(node);
+ if (node == NULL) {
+ *out = start + bitmap->start;
+ return 0;
+ }
+ ext = node_to_extent(node);
+ }
+ return ENOENT;
+}
+
+static errcode_t rb_find_first_set(ext2fs_generic_bitmap bitmap,
+ __u64 start, __u64 end, __u64 *out)
+{
+ struct rb_node *parent = NULL, **n;
+ struct rb_node *node, *next;
+ struct ext2fs_rb_private *bp;
+ struct bmap_rb_extent *ext;
+ int retval = 1;
+
+ bp = (struct ext2fs_rb_private *) bitmap->private;
+ n = &bp->root.rb_node;
+ start -= bitmap->start;
+ end -= bitmap->start;
+
+ if (start > end)
+ return EINVAL;
+
+ if (EXT2FS_RB_EMPTY_ROOT(&bp->root))
+ return ENOENT;
+
+ while (*n) {
+ parent = *n;
+ ext = node_to_extent(parent);
+ if (start < ext->start) {
+ n = &(*n)->rb_left;
+ } else if (start >= (ext->start + ext->count)) {
+ n = &(*n)->rb_right;
+ } else {
+ /* The start bit is set */
+ *out = start + bitmap->start;
+ return 0;
+ }
+ }
+
+ node = parent;
+ ext = node_to_extent(node);
+ if (ext->start < start) {
+ node = ext2fs_rb_next(node);
+ if (node == NULL)
+ return ENOENT;
+ ext = node_to_extent(node);
+ }
+ if (ext->start <= end) {
+ *out = ext->start + bitmap->start;
+ return 0;
+ }
+ return ENOENT;
+}
+
#ifdef BMAP_STATS
static void rb_print_stats(ext2fs_generic_bitmap bitmap)
{
@@ -890,4 +1002,6 @@ struct ext2_bitmap_ops ext2fs_blkmap64_rbtree = {
.get_bmap_range = rb_get_bmap_range,
.clear_bmap = rb_clear_bmap,
.print_stats = rb_print_stats,
+ .find_first_zero = rb_find_first_zero,
+ .find_first_set = rb_find_first_set,
};
--
1.8.5.rc3.362.gdf10213
--
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