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file-systems: Allow swap space lookup by UUID/label.

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* gnu/build/file-systems.scm (%linux-swap-magic, %page-size): New
variables.
(linux-swap-superblock?, read-linux-swap-superblock)
(linux-swap-superblock-uuid, linux-swap-superblock-volume-name): New
procedures.
(%partition-label-readers, %partition-uuid-readers): Add them.
This commit is contained in:
Ludovic Courtès 2020-10-22 23:28:31 +02:00
parent 6f1c9c3411
commit 11e19555e5
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GPG key ID: 090B11993D9AEBB5
1 changed files with 45 additions and 1 deletions
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46
gnu/build/file-systems.scm
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@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2014, 2015, 2016, 2017, 2018, 2020 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2016, 2017 David Craven <david@craven.ch>
;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
;;; Copyright © 2019 Guillaume Le Vaillant <glv@posteo.net>
@ -179,6 +179,46 @@ (define (check-ext2-file-system device)
(2 'reboot-required)
(_ 'fatal-error)))
;;;
;;; Linux swap.
;;;
;; Linux "swap space" is not a file system but it has a UUID and volume name,
;; like actual file systems, and we want to be able to look up swap partitions
;; by UUID and by label.
(define %linux-swap-magic
(string->utf8 "SWAPSPACE2"))
;; Like 'PAGE_SIZE' in Linux, arch/x86/include/asm/page.h.
;; XXX: This is always 4K on x86_64, i386, and ARMv7. However, on AArch64,
;; this is determined by 'CONFIG_ARM64_PAGE_SHIFT' in the kernel, which is 12
;; by default (4K) but can be 14 or 16.
(define %page-size 4096)
(define (linux-swap-superblock? sblock)
"Return #t when SBLOCK is an linux-swap superblock."
(and (= (bytevector-length sblock) %page-size)
(bytevector=? (sub-bytevector sblock (- %page-size 10) 10)
%linux-swap-magic)))
(define (read-linux-swap-superblock device)
"Return the raw contents of DEVICE's linux-swap superblock as a bytevector, or #f
if DEVICE does not contain an linux-swap file system."
(read-superblock device 0 %page-size linux-swap-superblock?))
;; See 'union swap_header' in 'include/linux/swap.h'.
(define (linux-swap-superblock-uuid sblock)
"Return the UUID of Linux-swap superblock SBLOCK as a 16-byte bytevector."
(sub-bytevector sblock (+ 1024 4 4 4) 16))
(define (linux-swap-superblock-volume-name sblock)
"Return the label of Linux-swap superblock SBLOCK as a string."
(null-terminated-latin1->string
(sub-bytevector sblock (+ 1024 4 4 4 16) 16)))
;;;
;;; Btrfs file systems.
@ -596,6 +636,8 @@ (define %partition-label-readers
iso9660-superblock-volume-name)
(partition-field-reader read-ext2-superblock
ext2-superblock-volume-name)
(partition-field-reader read-linux-swap-superblock
linux-swap-superblock-volume-name)
(partition-field-reader read-btrfs-superblock
btrfs-superblock-volume-name)
(partition-field-reader read-fat32-superblock
@ -612,6 +654,8 @@ (define %partition-uuid-readers
iso9660-superblock-uuid)
(partition-field-reader read-ext2-superblock
ext2-superblock-uuid)
(partition-field-reader read-linux-swap-superblock
linux-swap-superblock-uuid)
(partition-field-reader read-btrfs-superblock
btrfs-superblock-uuid)
(partition-field-reader read-fat32-superblock