From a624f1616731da6113ab9c6613be733ab41e664b Mon Sep 17 00:00:00 2001 From: Pavel Kretov Date: Wed, 25 Oct 2017 01:47:45 +0300 Subject: [PATCH] btrfs-progs: defrag: add a brief warning about ref-link breakage There is a warning in btrfs-filesystem(8) saying that running 'defrag' in Linux will almost certainly break ref-links, with much data potentially being physically duplicated. However, many users tend to read man pages *after* trying to run things on their own risk and may miss this important information. This commit adds a brief copy of this warning into the command built-in help message where it has good chances to be spotted before user is stuck with a crowded filesystem. Pull-request: #73 Signed-off-by: Pavel Kretov Signed-off-by: David Sterba --- cmds-filesystem.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/cmds-filesystem.c b/cmds-filesystem.c index c39f2d1..46aa497 100644 --- a/cmds-filesystem.c +++ b/cmds-filesystem.c @@ -893,6 +893,11 @@ static const char * const cmd_filesystem_defrag_usage[] = { "-s start defragment only from byte onward", "-l len defragment only up to len bytes", "-t size target extent size hint (default: 32M)", + "", + "Warning: most Linux kernels will break up the ref-links of COW data", + "(e.g., files copied with 'cp --reflink', snapshots) which may cause", + "considerable increase of space usage. See btrfs-filesystem(8) for", + "more information.", NULL }; -- 2.7.4