btrfs-progs: docs: update wording for compression mount options

Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/Documentation/btrfs-man5.asciidoc b/Documentation/btrfs-man5.asciidoc
index d446b6f..8d9031f 100644 (file)
--- a/Documentation/btrfs-man5.asciidoc
+++ b/Documentation/btrfs-man5.asciidoc
@@ -120,10 +120,15 @@ but a warning is printed if it's more than 300 seconds (5 minutes).
 Control BTRFS file data compression.  Type may be specified as 'zlib',
 'lzo' or 'no' (for no compression, used for remounting).  If no type
 is specified, 'zlib' is used.  If 'compress-force' is specified,
-all files will be compressed, whether or not they compress well. Otherwise
-some simple heuristics are applied to detect an incompressible file. If the
-first blocks written to a file are not compressible, the whole file is
-permanently marked to skip compression.
+the compression will allways be attempted, but the data may end up uncompressed
+if the compression would make them larger.
++
+Otherwise some simple heuristics are applied to detect an incompressible file.
+If the first blocks written to a file are not compressible, the whole file is
+permanently marked to skip compression. As this is too simple, the
+'compress-force' is a workaround that will compress most of the files at the
+cost of some wasted CPU cycles on failed attempts. The heuristics of 'compress'
+will improve in the future so this will not be necessary.
 +
 NOTE: If compression is enabled, 'nodatacow' and 'nodatasum' are disabled.