From: Steven Liu <lingjiujianke@gmail.com>
To: Robin Dong <hao.bigrat@gmail.com>
Cc: linux-ext4@vger.kernel.org, Robin Dong <sanbai@taobao.com>
Subject: Re: [PATCH v3] ext4: avoid wasted extent cache lookup if !PUNCH_OUT_EXT
Date: Wed, 29 Jun 2011 09:30:57 +0800 [thread overview]
Message-ID: <BANLkTinTk-2005wzEnLtk=guuOCnFdLBDA@mail.gmail.com> (raw)
In-Reply-To: <1309309071-2244-1-git-send-email-sanbai@taobao.com>
2011/6/29 Robin Dong <hao.bigrat@gmail.com>:
> 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>
> Reviewed-by: Lukas Czerner <lczerner@redhat.com>
> Reviewed-by: Eric Gouriou <egouriou@google.com>
> ---
> fs/ext4/extents.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index eb63c7b..fed2633 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3358,8 +3358,8 @@ 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) {
Ronbin Dong,
why donnot do this line?
if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
TO
if (!(flags & EXT4_GET_BLOCKS_CREATE) ) {
?
Acked-by: LiuQi <lingjiujianke@gmail.com>
> /*
> --
> 1.7.1
>
> --
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next prev parent reply other threads:[~2011-06-29 1:30 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-29 0:57 [PATCH v3] ext4: avoid wasted extent cache lookup if !PUNCH_OUT_EXT Robin Dong
2011-06-29 1:30 ` Steven Liu [this message]
2011-07-18 3:28 ` Ted Ts'o
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