rm(1): clarify that -P works only when blocks are updated in-place

Suggested by:	pjd, ivoras, arundel

2 files changed, 6 insertions, 6 deletions

diff --git a/bin/rm/rm.1 b/bin/rm/rm.1
index f580d33..11bc77d 100644
--- a/bin/rm/rm.1
+++ b/bin/rm/rm.1
@@ -32,7 +32,7 @@
 .\"	@(#)rm.1	8.5 (Berkeley) 12/5/94
 .\" $FreeBSD$
 .\"
-.Dd October 3, 2010
+.Dd October 8, 2010
 .Dt RM 1
 .Os
 .Sh NAME
@@ -229,8 +229,8 @@ command appeared in
 .Sh BUGS
 The
 .Fl P
-option assumes that the underlying file system is a fixed-block file
-system.
-UFS is a fixed-block file system, LFS is not.
+option assumes that the underlying file system updates existing blocks
+in-place and does not store new data in a new location.
+This is true for UFS but not for ZFS, which is using a Copy-On-Write strategy.
 In addition, only regular files are overwritten, other types of files
 are not.
diff --git a/bin/rm/rm.c b/bin/rm/rm.c
index d9bd296..653833a 100644
--- a/bin/rm/rm.c
+++ b/bin/rm/rm.c
@@ -402,8 +402,8 @@ rm_file(char **argv)
  * This is a cheap way to *really* delete files.  Note that only regular
  * files are deleted, directories (and therefore names) will remain.
  * Also, this assumes a fixed-block file system (like FFS, or a V7 or a
- * System V file system).  In a logging file system, you'll have to have
- * kernel support.
+ * System V file system).  In a logging or COW file system, you'll have to
+ * have kernel support.
  */
 int
 rm_overwrite(char *file, struct stat *sbp)