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-rw-r--r--gnu/build/file-systems.scm46
1 files changed, 44 insertions, 2 deletions
diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm
index e76854490c..6e5c6aaf15 100644
--- a/gnu/build/file-systems.scm
+++ b/gnu/build/file-systems.scm
@@ -146,6 +146,43 @@ if DEVICE does not contain an ext2 file system."
;;;
+;;; Btrfs file systems.
+;;;
+
+;; <https://btrfs.wiki.kernel.org/index.php/On-disk_Format#Superblock>.
+
+(define-syntax %btrfs-endianness
+ ;; Endianness of btrfs file systems.
+ (identifier-syntax (endianness little)))
+
+(define (btrfs-superblock? sblock)
+ "Return #t when SBLOCK is a btrfs superblock."
+ (bytevector=? (sub-bytevector sblock 64 8)
+ (string->utf8 "_BHRfS_M")))
+
+(define (read-btrfs-superblock device)
+ "Return the raw contents of DEVICE's btrfs superblock as a bytevector, or #f
+if DEVICE does not contain a btrfs file system."
+ (read-superblock device 65536 4096 btrfs-superblock?))
+
+(define (btrfs-superblock-uuid sblock)
+ "Return the UUID of a btrfs superblock SBLOCK as a 16-byte bytevector."
+ (sub-bytevector sblock 32 16))
+
+(define (btrfs-superblock-volume-name sblock)
+ "Return the volume name of SBLOCK as a string of at most 256 characters, or
+#f if SBLOCK has no volume name."
+ (null-terminated-latin1->string (sub-bytevector sblock 299 256)))
+
+(define (check-btrfs-file-system device)
+ "Return the health of a btrfs file system on DEVICE."
+ (match (status:exit-val
+ (system* "btrfs" "device" "scan"))
+ (0 'pass)
+ (_ 'fatal-error)))
+
+
+;;;
;;; LUKS encrypted devices.
;;;
@@ -257,11 +294,15 @@ partition field reader that returned a value."
(define %partition-label-readers
(list (partition-field-reader read-ext2-superblock
- ext2-superblock-volume-name)))
+ ext2-superblock-volume-name)
+ (partition-field-reader read-btrfs-superblock
+ btrfs-superblock-volume-name)))
(define %partition-uuid-readers
(list (partition-field-reader read-ext2-superblock
- ext2-superblock-uuid)))
+ ext2-superblock-uuid)
+ (partition-field-reader read-btrfs-superblock
+ btrfs-superblock-uuid)))
(define read-partition-label
(cut read-partition-field <> %partition-label-readers))
@@ -428,6 +469,7 @@ the following:
(define check-procedure
(cond
((string-prefix? "ext" type) check-ext2-file-system)
+ ((string-prefix? "btrfs" type) check-btrfs-file-system)
(else #f)))
(if check-procedure