Re: [PATCH 1/2] Btrfs: don't compress for a small write

[Chris Mason <clm@fb.com>]

On 03/24/2014 05:58 AM, Wang Shilong wrote:
> To compress a small write(<=blocksize) dosen't save us
> disk space at all, skip it can save us some compression time.
>
> This patch can also fix wrong setting nocompression flag for
> inode, say a case when @total_in is 4096, and then we get
> @total_compressed 52,because we do aligment to page cache size
> firstly, and then we get into conclusion @total_in=@total_compressed
> thus we will clear this inode's compression flag.
>
> An exception comes from inserting inline extent failure but we
> still have @total_compressed < @total_in,so we will still reset
> inode's flag, this is ok, because we don't have good compression
> effect.
>

So your check for start > 0 || end + 1 < disk_i_size means we're only 
skipping compression for a small file range that isn't in an inline 
extent.   Could you please update the patch description and comments in 
the code to reflect this?

Thanks!

-chris