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ext4: avoid wasted extent cache lookup if !PUNCH_OUT_EXT 

This patch avoids an extraneous lookup of the extent cache
in ext4_ext_map_blocks() when the flag
EXT4_GET_BLOCKS_PUNCH_OUT_EXT is absent.

The existing logic was performing the lookup but not making
use of the result. The patch simply reverses the order of evaluation
in the condition.

Since ext4_ext_in_cache() does not initialize newex on misses, bypassing
its invocation does not introduce any new issue in this regard.

Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Eric Gouriou <egouriou@google.com>
This commit is contained in:
Robin Dong 2011-07-17 23:27:43 -04:00 committed by Theodore Ts'o
parent c6a0371cbe
commit 015861badd
1 changed files with 2 additions and 2 deletions
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4
fs/ext4/extents.c
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@ -3320,8 +3320,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
trace_ext4_ext_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
/* check in cache */
if (ext4_ext_in_cache(inode, map->m_lblk, &newex) &&
((flags & EXT4_GET_BLOCKS_PUNCH_OUT_EXT) == 0)) {
if (!(flags & EXT4_GET_BLOCKS_PUNCH_OUT_EXT) &&
ext4_ext_in_cache(inode, map->m_lblk, &newex)) {
if (!newex.ee_start_lo && !newex.ee_start_hi) {
if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
/*