From a98db793cffb77a8794c854443b8fe12bad98c0a Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Thu, 16 Mar 2017 17:45:07 +0100 Subject: [PATCH] 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 --- util-linux/umount.c | 24 ++++++++---------------- 1 file 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);