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author | Zheng Liu <wenqing.lz@taobao.com> | 2013-02-18 09:29:59 +0400 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2013-02-18 09:29:59 +0400 |
commit | d100eef2440fea13e4f09e88b1c8bcbca64beb9f (patch) | |
tree | 2451dc4582b43a30b414c89108b75148d48c9b57 /fs/ext4/extents_status.c | |
parent | f7fec032aa782d3fd7e51fbdf08aa3a296c01500 (diff) | |
download | linux-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.c | 60 |
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) { |