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ext4: lookup block mapping in extent status tree

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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>
This commit is contained in:
Zheng Liu
2013-02-18 00:29:59 -05:00
committed by Theodore Ts'o
parent f7fec032aa
commit d100eef244
6 changed files with 192 additions and 3 deletions
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9
fs/ext4/extents.c
View File

@@ -2167,6 +2167,9 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
block,
le32_to_cpu(ex->ee_block),
ext4_ext_get_actual_len(ex));
if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))
ext4_es_insert_extent(inode, lblock, len, ~0,
EXTENT_STATUS_HOLE);
} else if (block >= le32_to_cpu(ex->ee_block)
+ ext4_ext_get_actual_len(ex)) {
ext4_lblk_t next;
@@ -2180,6 +2183,9 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
block);
BUG_ON(next == lblock);
len = next - lblock;
if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))
ext4_es_insert_extent(inode, lblock, len, ~0,
EXTENT_STATUS_HOLE);
} else {
lblock = len = 0;
BUG();
@@ -4018,7 +4024,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
* put just found gap into cache to speed up
* subsequent requests
*/
ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);
if ((flags & EXT4_GET_BLOCKS_NO_PUT_HOLE) == 0)
ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);
goto out2;
}