From 68bb462d42a963169bf7acbe106aae08c17129a5 Mon Sep 17 00:00:00 2001 From: Wang Shilong <wangsl.fnst@cn.fujitsu.com> Date: Tue, 1 Apr 2014 18:01:42 +0800 Subject: [PATCH] Btrfs: don't compress for a small write To compress a small file range(<=blocksize) that is not an inline extent can not save disk space at all. skip it can save us some cpu 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. Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com> Signed-off-by: Chris Mason <clm@fb.com> --- fs/btrfs/inode.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 251db68148b23..fdb8f4486e854 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -394,6 +394,14 @@ static noinline int compress_file_range(struct inode *inode, (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size)) btrfs_add_inode_defrag(NULL, inode); + /* + * skip compression for a small file range(<=blocksize) that + * isn't an inline extent, since it dosen't save disk space at all. + */ + if ((end - start + 1) <= blocksize && + (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size)) + goto cleanup_and_bail_uncompressed; + actual_end = min_t(u64, isize, end + 1); again: will_compress = 0; -- 2.49.0