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authorZheng Liu <wenqing.lz@taobao.com>2013-02-18 09:29:59 +0400
committerTheodore Ts'o <tytso@mit.edu>2013-02-18 09:29:59 +0400
commitd100eef2440fea13e4f09e88b1c8bcbca64beb9f (patch)
tree2451dc4582b43a30b414c89108b75148d48c9b57 /fs/ext4/extents_status.c
parentf7fec032aa782d3fd7e51fbdf08aa3a296c01500 (diff)
downloadlinux-d100eef2440fea13e4f09e88b1c8bcbca64beb9f.tar.xz
ext4: lookup block mapping in extent status tree
After tracking all extent status, we already have a extent cache in memory. Every time we want to lookup a block mapping, we can first try to lookup it in extent status tree to avoid a potential disk I/O. A new function called ext4_es_lookup_extent is defined to finish this work. When we try to lookup a block mapping, we always call ext4_map_blocks and/or ext4_da_map_blocks. So in these functions we first try to lookup a block mapping in extent status tree. A new flag EXT4_GET_BLOCKS_NO_PUT_HOLE is used in ext4_da_map_blocks in order not to put a hole into extent status tree because this hole will be converted to delayed extent in the tree immediately. Signed-off-by: Zheng Liu <wenqing.lz@taobao.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: Jan kara <jack@suse.cz>
Diffstat (limited to 'fs/ext4/extents_status.c')
-rw-r--r--fs/ext4/extents_status.c60
1 files changed, 60 insertions, 0 deletions
diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 76f4351ea821..eeb893122d8d 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -461,6 +461,66 @@ error:
return err;
}
+/*
+ * ext4_es_lookup_extent() looks up an extent in extent status tree.
+ *
+ * ext4_es_lookup_extent is called by ext4_map_blocks/ext4_da_map_blocks.
+ *
+ * Return: 1 on found, 0 on not
+ */
+int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk,
+ struct extent_status *es)
+{
+ struct ext4_es_tree *tree;
+ struct extent_status *es1 = NULL;
+ struct rb_node *node;
+ int found = 0;
+
+ trace_ext4_es_lookup_extent_enter(inode, lblk);
+ es_debug("lookup extent in block %u\n", lblk);
+
+ tree = &EXT4_I(inode)->i_es_tree;
+ read_lock(&EXT4_I(inode)->i_es_lock);
+
+ /* find extent in cache firstly */
+ es->es_lblk = es->es_len = es->es_pblk = 0;
+ if (tree->cache_es) {
+ es1 = tree->cache_es;
+ if (in_range(lblk, es1->es_lblk, es1->es_len)) {
+ es_debug("%u cached by [%u/%u)\n",
+ lblk, es1->es_lblk, es1->es_len);
+ found = 1;
+ goto out;
+ }
+ }
+
+ node = tree->root.rb_node;
+ while (node) {
+ es1 = rb_entry(node, struct extent_status, rb_node);
+ if (lblk < es1->es_lblk)
+ node = node->rb_left;
+ else if (lblk > ext4_es_end(es1))
+ node = node->rb_right;
+ else {
+ found = 1;
+ break;
+ }
+ }
+
+out:
+ if (found) {
+ BUG_ON(!es1);
+ es->es_lblk = es1->es_lblk;
+ es->es_len = es1->es_len;
+ es->es_pblk = es1->es_pblk;
+ }
+
+ read_unlock(&EXT4_I(inode)->i_es_lock);
+
+ trace_ext4_es_lookup_extent_exit(inode, es, found);
+ return found;
+}
+
static int __es_remove_extent(struct ext4_es_tree *tree, ext4_lblk_t lblk,
ext4_lblk_t end)
{