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authorWang Shilong <wangsl.fnst@cn.fujitsu.com>2014-04-01 18:01:42 +0800
committerChris Mason <clm@fb.com>2014-04-07 09:08:48 -0700
commit68bb462d42a963169bf7acbe106aae08c17129a5 (patch)
tree91cfa510c89128399c87371f9ffc974654c24a46
parentc50d3e71c3d0378bcc9e116f48dab4148854a7bb (diff)
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>
-rw-r--r--fs/btrfs/inode.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 251db68148b2..fdb8f4486e85 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;