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-rw-r--r--guix/build/syscalls.scm22
1 files changed, 22 insertions, 0 deletions
diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index d75c11ada7..6f2a061f35 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -73,6 +73,7 @@
file-system-mount-flags
statfs
free-disk-space
+ device-in-use?
processes
mkdtemp!
@@ -684,6 +685,27 @@ mounted at FILE."
(define AT_NO_AUTOMOUNT #x800)
(define AT_EMPTY_PATH #x1000)
+(define-syntax BLKRRPART ;<sys/mount.h>
+ (identifier-syntax #x125F))
+
+(define* (device-in-use? device)
+ "Return #t if the block DEVICE is in use, #f otherwise. This is inspired
+from fdisk_device_is_used function of util-linux. This is particulary useful
+for devices that do not appear in /proc/self/mounts like overlayfs lowerdir
+backend device."
+ (let*-values (((port) (open-file device "rb"))
+ ((ret err) (%ioctl (fileno port) BLKRRPART %null-pointer)))
+ (close-port port)
+ (cond
+ ((= ret 0)
+ #f)
+ ((= err EBUSY)
+ #t)
+ (else
+ (throw 'system-error "ioctl" "~A"
+ (list (strerror err))
+ (list err))))))
+
;;;
;;; Containers.