[PATCH] swsusp: document support for swap files

Document the "resume_offset=" command line parameter as well as the way in
which swap files are supported by swsusp.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 13 deletions

diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt
index e635e6f1e316..0761ff6c57ed 100644
--- a/Documentation/power/swsusp.txt
+++ b/Documentation/power/swsusp.txt
@@ -297,20 +297,12 @@ system is shut down or suspended. Additionally use the encrypted
 suspend image to prevent sensitive data from being stolen after
 resume.
 
-Q: Why can't we suspend to a swap file?
+Q: Can I suspend to a swap file?
 
-A: Because accessing swap file needs the filesystem mounted, and
-filesystem might do something wrong (like replaying the journal)
-during mount.
-
-There are few ways to get that fixed:
-
-1) Probably could be solved by modifying every filesystem to support
-some kind of "really read-only!" option. Patches welcome.
-
-2) suspend2 gets around that by storing absolute positions in on-disk
-image (and blocksize), with resume parameter pointing directly to
-suspend header.
+A: Generally, yes, you can.  However, it requires you to use the "resume=" and
+"resume_offset=" kernel command line parameters, so the resume from a swap file
+cannot be initiated from an initrd or initramfs image.  See
+swsusp-and-swap-files.txt for details.
 
 Q: Is there a maximum system RAM size that is supported by swsusp?