Messages in this thread | | | Date | Thu, 29 Jun 2023 17:33:31 +0200 | From | David Sterba <> | Subject | Re: [PATCH] fs: btrfs: Optimize code execution process to save time |
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On Mon, Jun 26, 2023 at 06:07:16PM +0800, Lu Hongfei wrote: > Originally, the btrfs_check_data_free_space used round_down twice when > aligning the range, which to some extent increased the execution time of > the code. > After optimization, round_down only needs to be executed once, which can > improve code efficiency and increase code readability.
But the code is not equivalent, because there is dependency on the value of start that changes when the line is moved.
> Signed-off-by: Lu Hongfei <luhongfei@vivo.com> > --- > fs/btrfs/delalloc-space.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/fs/btrfs/delalloc-space.c b/fs/btrfs/delalloc-space.c > index 427abaf608b8..fd33b1cf1954 100644 > --- a/fs/btrfs/delalloc-space.c > +++ b/fs/btrfs/delalloc-space.c > @@ -137,9 +137,8 @@ int btrfs_check_data_free_space(struct btrfs_inode *inode, > int ret; > > /* align the range */ > - len = round_up(start + len, fs_info->sectorsize) - > - round_down(start, fs_info->sectorsize);
Start is used unchanged, start + len
> start = round_down(start, fs_info->sectorsize); > + len = round_up(start + len, fs_info->sectorsize) - start;
New code uses the rounded down start for round_up, then for "- start" it's the same (that part is ok).
The changelog should explain why the code is still doing the same, not just that it's reducing the number of round_down() calls.
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