From: Karel Zak <kzak@redhat.com>
Date: Mon, 21 Jan 2019 11:44:49 +0000 (+0100)
Subject: swapon: (man) cleanup note about holes
X-Git-Tag: v2.34-rc1~150
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=eebfa469fcd07eb020dc4d6f1ae1a661d4b365ee;p=thirdparty%2Futil-linux.git

swapon: (man) cleanup note about holes

Addresses: https://github.com/karelzak/util-linux/issues/633
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/disk-utils/mkswap.8 b/disk-utils/mkswap.8
index 27f9221718..bdc631491c 100644
--- a/disk-utils/mkswap.8
+++ b/disk-utils/mkswap.8
@@ -130,17 +130,18 @@ e.g.\& using a command like
 
 to create 8GiB swapfile.
 
-Note that a swap file must not contain any holes.  Using
+The swap file implementation in the kernel expects to be able to write to the file directly,
+without the assistance of the filesystem.  This is a problem on files with holes
+(e.g. created by
 .BR cp (1)
-to create the file is not acceptable.  Neither is use of
-.BR fallocate (1)
-on file systems that support preallocated files, such as
-.BR XFS " or " ext4 ,
-or on copy-on-write filesystems like
+or another commands), or on files on copy-on-write filesystems like
 .BR btrfs .
-It is recommended to use
+In some cases preallocated files (e.g. fallocate(1) on XFS) maybe interpreted
+by kernel as files with holes too.  The most portable solution is to use
 .BR dd (1)
-and /dev/zero in these cases.  Please read notes from
+and /dev/zero in these cases.
+.sp
+Please read notes from
 .BR swapon (8)
 before adding a swap file to copy-on-write filesystems.
 
diff --git a/sys-utils/swapon.8 b/sys-utils/swapon.8
index 510a15fd01..aea45b2f58 100644
--- a/sys-utils/swapon.8
+++ b/sys-utils/swapon.8
@@ -195,18 +195,16 @@ This can be seen in the system log as
 .B "swapon: swapfile has holes."
 .sp
 .RE
-The swap file implementation in the kernel expects to be able to write to the
-file directly, without the assistance of the filesystem.  This is a problem on
-preallocated files (e.g.
-.BR fallocate (1))
-on filesystems like \fBXFS\fR or \fBext4\fR, and on copy-on-write
-filesystems like \fBbtrfs\fR.
-.PP
-It is recommended to use
+The swap file implementation in the kernel expects to be able to write to the file directly,
+without the assistance of the filesystem.  This is a problem on files with holes
+(e.g. created by
+.BR cp (1)
+or another commands), or on files on copy-on-write filesystems like
+.BR btrfs .
+In some cases preallocated files (e.g. fallocate(1) on XFS) maybe interpreted
+by kernel as files with holes too.  The most portable solution is to use
 .BR dd (1)
-and
-.I /dev/zero
-to avoid holes on XFS and ext4.
+and /dev/zero in these cases.
 .PP
 .B swapon
 may not work correctly when using a swap file with some versions of