Commit 015861ba authored Jul 17, 2011 by Robin Dong Committed by Theodore Ts'o Jul 17, 2011

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>

parent c6a0371c

fs/ext4/extents.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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) {
		/*

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