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authorGravatar Denys Vlasenko <vda.linux@googlemail.com>2017-03-16 17:45:07 +0100
committerGravatar Denys Vlasenko <vda.linux@googlemail.com>2017-03-16 17:51:06 +0100
commita98db793cffb77a8794c854443b8fe12bad98c0a (patch)
treeeb5128d5a91ef821331fa12c8204c1d642d99daa
parentab518eea9c41235a3fcde80f3ea99669eaade621 (diff)
downloadbusybox-a98db793cffb77a8794c854443b8fe12bad98c0a.tar.gz
busybox-a98db793cffb77a8794c854443b8fe12bad98c0a.tar.bz2
Revert "umount: make -d always active, add -D to suppress it"
This reverts commit 86a03bee1d3d6990c03bf500836b19ec8a1c1f12. Since now our "mount -oloop" creates AUTOCLEARed loopdevs, we no longer need our umount to destroy loopdevs to match the usual util-linux behaviour. Now this revert fixes another, opposite bug: "explicit" mount /dev/loopN and then umount must not drop loopdevs! User complaint is as follows: It seems LOOP_CLR_FD called on a loop-*partition* removes the mapping of the whole *device* - which results in the following: root@LEDE:/# loop=$(losetup -f) root@LEDE:/# echo ${loop} /dev/loop2 root@LEDE:/# losetup ${loop} /IMAGE root@LEDE:/# ls -l ${loop}* brw------- 1 root root 7, 2 Mar 6 20:09 /dev/loop2 root@LEDE:/# partprobe ${loop} root@LEDE:/# ls -l ${loop}* brw------- 1 root root 7, 2 Mar 6 20:09 /dev/loop2 brw------- 1 root root 259, 8 Mar 6 21:59 /dev/loop2p1 brw------- 1 root root 259, 9 Mar 6 21:59 /dev/loop2p2 brw------- 1 root root 259, 10 Mar 6 21:59 /dev/loop2p3 brw------- 1 root root 259, 11 Mar 6 21:59 /dev/loop2p4 brw------- 1 root root 259, 12 Mar 6 21:59 /dev/loop2p5 brw------- 1 root root 259, 13 Mar 6 21:59 /dev/loop2p6 brw------- 1 root root 259, 14 Mar 6 21:59 /dev/loop2p7 brw------- 1 root root 259, 15 Mar 6 21:59 /dev/loop2p8 root@LEDE:/# mount ${loop}p8 /MOUNT # mount loop partition root@LEDE:/# losetup -a | grep $loop # loop dev mapping still there /dev/loop2: 0 /mnt/IMAGE root@LEDE:/# strace umount /MOUNT 2> /log # unmount loop partition root@LEDE:/# losetup -a | grep ${loop} # loop device mapping is gone root@LEDE:/# grep -i loop /log open("/dev/loop2p7", O_RDONLY|O_LARGEFILE) = 3 ioctl(3, LOOP_CLR_FD) = 0 root@LEDE:/# The strace was done to figure out, if maybe umount wrongly ioctl()'s the parent device instead of the partition - it doesn't. I already wasn't a fan of umount implicitly removing the mapping in the first place (as I usually setup and release loop devices with `losetup` and scripts needed to call umount differently in order to work and outside busybox). However taking above (kernel-)behaviour into account - umount calling ioctl(LOOP_CLR_FD) unconditionally potentially causes some nasty side effects Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--util-linux/umount.c24
1 files changed, 8 insertions, 16 deletions
diff --git a/util-linux/umount.c b/util-linux/umount.c
index c958fd552..0c50dc9ee 100644
--- a/util-linux/umount.c
+++ b/util-linux/umount.c
@@ -42,7 +42,7 @@
//usage: "\n -l Lazy umount (detach filesystem)"
//usage: "\n -f Force umount (i.e., unreachable NFS server)"
//usage: IF_FEATURE_MOUNT_LOOP(
-//usage: "\n -D Don't free loop device even if it has been used"
+//usage: "\n -d Free loop device if it has been used"
//usage: )
//usage:
//usage:#define umount_example_usage
@@ -68,22 +68,14 @@ static struct mntent *getmntent_r(FILE* stream, struct mntent* result,
}
#endif
-/* Ignored: -v -t -i
- * bbox always acts as if -d is present.
- * -D can be used to suppress it (bbox extension).
- * Rationale:
- * (1) util-linux's umount does it if "loop=..." is seen in /etc/mtab:
- * thus, on many systems, bare umount _does_ drop loop devices.
- * (2) many users request this feature.
- */
-#define OPTION_STRING "fldDnra" "vt:i"
+/* ignored: -v -t -i */
+#define OPTION_STRING "fldnra" "vt:i"
#define OPT_FORCE (1 << 0) // Same as MNT_FORCE
#define OPT_LAZY (1 << 1) // Same as MNT_DETACH
-//#define OPT_FREE_LOOP (1 << 2) // -d is assumed always present
-#define OPT_DONT_FREE_LOOP (1 << 3)
-#define OPT_NO_MTAB (1 << 4)
-#define OPT_REMOUNT (1 << 5)
-#define OPT_ALL (ENABLE_FEATURE_UMOUNT_ALL ? (1 << 6) : 0)
+#define OPT_FREELOOP (1 << 2)
+#define OPT_NO_MTAB (1 << 3)
+#define OPT_REMOUNT (1 << 4)
+#define OPT_ALL (ENABLE_FEATURE_UMOUNT_ALL ? (1 << 5) : 0)
int umount_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int umount_main(int argc UNUSED_PARAM, char **argv)
@@ -206,7 +198,7 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
} else {
// De-allocate the loop device. This ioctl should be ignored on
// any non-loop block devices.
- if (ENABLE_FEATURE_MOUNT_LOOP && !(opt & OPT_DONT_FREE_LOOP) && m)
+ if (ENABLE_FEATURE_MOUNT_LOOP && (opt & OPT_FREELOOP) && m)
del_loop(m->device);
if (ENABLE_FEATURE_MTAB_SUPPORT && !(opt & OPT_NO_MTAB) && m)
erase_mtab(m->dir);