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file-systems: Add support for hibernation swap detection.

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* gnu/build/file-systems.scm (%linux-swsuspend-magic): New variable.
(linux-swsuspend-superblock?, read-linux-swsuspend-superblock): New
procedures.
(%partition-label-readers, %partition-uuid-readers): Add readers for
linux-swsuspend superblocks.

Change-Id: If77ca9b4ae1f72c4e9ce52149b10d331566b0030
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
This commit is contained in:
Jean-Baptiste Note 2025-09-11 21:10:22 +02:00 • committed by Ludovic Courtès
parent f2c3ff8cba
commit ec13537053
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37
gnu/build/file-systems.scm
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@ -336,6 +336,39 @@ negative, defaulting to 0.~%") p)
0))
(logior prio-flag delayed-flag))
;;;
;;; Linux swap, after hibernation.
;;;
;; Linux swap space header is rewritten with a swsusp_header on
;; hibernate, which takes the HIBERNATE_SIG signature, which is this
;; string; see function mark_swapfiles in kernel/power/swap.c. In the
;; linux kernel the comparison is always done on 10 bytes, which
;; include the trailing zero in the case of HIBERNATE_SIG while not
;; including it for %linux-swap-magic.
(define %linux-swsuspend-magic
(string->utf8 "S1SUSPEND\0"))
;; The kernel structure swsusp_header is duplicated from the swap header, in
;; kernel/power/swap.c.
(define (linux-swsuspend-superblock? sblock)
"Return #t when SBLOCK is a linux-swap superblock we can resume from."
(and (= (bytevector-length sblock) %page-size)
(bytevector=? (sub-bytevector sblock (- %page-size 10) 10)
%linux-swsuspend-magic)))
;; If we want to resume through UUID and/or LABEL from swap partitions, we
;; need to fetch UUID/LABEL from partitions with such magics.
(define (read-linux-swsuspend-superblock device)
"Return the raw contents of DEVICE's linux-swsuspend superblock as a
bytevector, or #f if DEVICE does not contain an linux-swap file system with an
hibernation image from which we can resume."
(read-superblock device 0 %page-size linux-swsuspend-superblock?))
;; Label and UUID information are otherwise left untouched, therefore, swap
;; functions are reused.
;;;
@ -1052,6 +1085,8 @@ partition field reader that returned a value."
ext2-superblock-volume-name)
(partition-field-reader read-linux-swap-superblock
linux-swap-superblock-volume-name)
(partition-field-reader read-linux-swsuspend-superblock
linux-swap-superblock-volume-name)
(partition-field-reader read-bcachefs-superblock
bcachefs-superblock-volume-name)
(partition-field-reader read-btrfs-superblock
@ -1076,6 +1111,8 @@ partition field reader that returned a value."
ext2-superblock-uuid)
(partition-field-reader read-linux-swap-superblock
linux-swap-superblock-uuid)
(partition-field-reader read-linux-swsuspend-superblock
linux-swap-superblock-uuid)
(partition-field-reader read-bcachefs-superblock
bcachefs-superblock-external-uuid)
(partition-field-reader read-btrfs-superblock