From 6cf0833a93bede5fe41e0f126267876fefbb3672 Mon Sep 17 00:00:00 2001
From: Jean-Baptiste Note <jean-baptiste.note@m4x.org>
Date: Mon, 27 Apr 2020 20:42:03 +0000
Subject: [PATCH] linux-boot: Add support for resuming from swap device.
* gnu/build/linux-boot.scm (resume-from-device): Add function.
* gnu/build/linux-boot.scm (boot-system): Add hook calling resume-from-device
if specified on commandline, before mounting any actual disk filesystems.
---
gnu/build/linux-boot.scm | 43 +++++++++++++++++++++++++++++++++++++---
1 file changed, 40 insertions(+), 3 deletions(-)
@@ -357,6 +357,37 @@ the last argument of `mknod'."
(compose (cut string=? program <>) basename))))
(filter-map string->number (scandir "/proc")))))
+(define (resume-from-device resume-device)
+ "Resume from hibernation state on RESUME-DEVICE. This *must* happen before
+we mount any filesystems on disk. See
+linux-libre/Documentation/power/swsusp.txt. Please note that this function
+will not return if resume happens successfully, and will return if swap device
+does not contain a valid resume signature."
+ (false-if-exception
+ (let* ((device-base-name
+ ;; The base name of the device file, after resolving
+ ;; symlinks.
+ (let loop ((file resume-device))
+ (match (stat:type (lstat file))
+ ('symlink
+ (let ((target (readlink file)))
+ (if (string-prefix? "/" target)
+ (loop target)
+ (loop (string-append (dirname file) "/" target)))))
+ (_ (basename file)))))
+ (major+minor
+ ;; The major:minor string (e.g. "8:2") corresponding
+ ;; to the resume device.
+ (call-with-input-file (string-append "/sys/class/block/"
+ device-base-name
+ "/dev")
+ read-line)))
+ ;; Write the major:minor string to /sys/power/resume
+ ;; to attempt resume from hibernation.
+ (when major+minor
+ (call-with-output-file "/sys/power/resume"
+ (cut display major+minor <>))))))
+
(define* (mount-root-file-system root type
#:key volatile-root? (flags 0) options)
"Mount the root file system of type TYPE at device ROOT. If VOLATILE-ROOT? is
@@ -493,9 +524,10 @@ upon error."
(call-with-error-handling
(lambda ()
(mount-essential-file-systems)
- (let* ((args (linux-command-line))
- (to-load (find-long-option "--load" args))
- (root (find-long-option "--root" args)))
+ (let* ((args (linux-command-line))
+ (to-load (find-long-option "--load" args))
+ (root (find-long-option "--root" args))
+ (resume-device (find-long-option "--resume" args)))
(when (member "--repl" args)
(start-repl))
@@ -528,6 +560,11 @@ upon error."
(unless (pre-mount)
(error "pre-mount actions failed")))
+ (when (and resume-device
+ (file-exists? resume-device)
+ (file-exists? "/sys/power/resume"))
+ (resume-from-device resume-device))
+
(setenv "EXT2FS_NO_MTAB_OK" "1")
(if root
--
2.26.2
Hi Danny, Thanks for being so guix in answering the original report. Your questions prompted me to take a bit of time before answering. Regarding attribution, i've dug two instances of this patch: https://git.pantherx.org/mirror/guix/commit/af8d58efa05927b24694c87379cccc378f3fdde7 https://issues.guix.gnu.org/issue/37290 https://lists.gnu.org/archive/html/bug-guix/2019-09/msg00017.html Both instances of the patch are given by author Mark H Weaver <mhw@netris.org> As you can see there's already an open issue in GUIX regarding resume; i'm sorry i missed that. Maybe for attribution it would make sense for me to resend the patch there; let me know how to proceed. Regarding the patch itself and your questions: - for comparison to the original patch: elogind currently has the configurability required to make the second half of the original patch moot, and I think it would be better to split the work anyways; - i've addressed the reference to swsusp.txt - the resume argument is provided by (in my case) the system definition, so I basically have something like that: #+begin_src scheme (operating-system (kernel-arguments (cons (string-append "modprobe.blacklist=" (comma-separated %redundant-linux-modules)) '("--resume=/dev/sdb3" "quiet")))) #end_src - in order to support this in the GUIX installer, I guess adding such a line in the generated system definition, along with a swap partition, would be sufficient. My knowledge of the workings of the guix installer is null, tough :) - please note that if you have a suspend signature on your swap partition, and fail to resume from it (for instance because of a missing kernel commandline argument...), then shepherd will fail bringing up the swap device, and you will need to handle this situation by hand currently; - My knowledge of the details of swsusp is rather limited: I don't know, for instance, how this would translate in case of a more complex setup of multi-swap devices; - However, it seems very clear from the documentation that a mere resume= argument syntax can trigger specific initialization paths within the kernel itself leading to a resume. I find it better style, ultimately, to properly separate the responsibilities of kernel and initrd, follow the GUIX conventions with a --resume argument. - therefore I propose the following, updated patch, with a more GUIX-like --resume argument; I've tested it on my laptop, which happens to have an encrypted /home partition (but only one swap device). - as far as I can understand the documentation, the swap partition does not have to be as big as the RAM; by default the kernel will strive to make the suspend image 2/5 of the physical RAM, but this can be tuned more aggressively. There's actually less than overhead: some parts of the memory can be discarded (shared MMAPd files, the buffer cache); and even then you can hope compression will reduce the needs. If the swap space is not large enough, suspend will simply fail. This probably raises more issues than it solves, however i'd rather you have the whole picture. Let me know how to proceed; I'm willing to follow-up with other patches to get the feature up to the required standards of quality. Kind regards, Jean-Baptiste