swapon: better text for "discard", note about swapon in fstab.5

Suggested by Hugh Dickins. Thanks.

Signed-off-by: Karel Zak <kzak@redhat.com>

2 files changed, 7 insertions, 4 deletions

diff --git a/mount/fstab.5 b/mount/fstab.5
index 99557194..cd5cf558 100644
--- a/mount/fstab.5
+++ b/mount/fstab.5
@@ -176,8 +176,11 @@ This field describes the mount options associated with the filesystem.
 
 It is formatted as a comma separated list of options.  It contains at least
 the type of mount plus any additional options appropriate to the filesystem
-type. For documentation on the available options, see
+type. For documentation on the available mount options, see
 .BR mount (8).
+For documentation on the available swap options, see
+.BR swapon (8).
+
 Basic file system independent options are:
 .TP
 .B defaults
diff --git a/mount/swapon.8 b/mount/swapon.8
index e35c6e5f..1fe62987 100644
--- a/mount/swapon.8
+++ b/mount/swapon.8
@@ -113,14 +113,14 @@ are made available, except for those with the ``noauto'' option.
 Devices that are already being used as swap are silently skipped.
 .TP
 .B "\-d, \-\-discard"
-Swapping will discard clusters of swap pages in between freeing them
-and re-writing to them, if the swap device supports that.
+Discard freed swap pages before they are reused, if the swap
+device supports the discard or trim operation.  This may improve
+performance on some Solid State Devices, but often it does not.
 The
 .I /etc/fstab
 mount option
 .BI discard
 may be also used to enable discard flag.
-
 .TP
 .B "\-e, \-\-ifexists"
 Silently skip devices that do not exist.