From 5d79666f8f7563ed9904a7ce2087f430ee2702b6 Mon Sep 17 00:00:00 2001 From: Valerie Aurora Date: Tue, 3 Aug 2010 20:09:19 -0400 Subject: mount: get most recently mounted fs from /etc/mtab. I spent most of the day tracking down this subtle remount bug. I think this is the correct solution but I'd appreciate some double-checking. I suspect this bug will munge the mount options whenever you remount a file system mounted on the same mountpoint as another file system, using the mountpoint as the handle. -VAL commit c010b3a0783430e2b94f3b3dc0929ae299e383eb Author: Valerie Aurora Date: Tue Aug 3 16:32:52 2010 -0700 mount: get most recently mounted fs from /etc/mtab. In mount, when using /etc/mtab to lookup a mount entry, get the most recently mounted entry instead of the first mounted entry. You want to manipulate the most recent mount, not a covered mount. See comment to umount_one_bw(). This bug has been util-linux-ng since the first git checkin. It finally showed up on my system with the change to stop using SETLOOP_AUTOCLEAR if /etc/mtab is writable (commit af092544). If you do a remount of a file system mounted on the same dir as another file system, it will take the options from the first mount and write them out to /etc/mtab as the options to the second mount - including, in the case of a loop device, loop=/dev/loop0. Then when you umount the second mount, it grabs the line from /etc/mtab and tries to tear down the loop device, which complains because it is still in use by the first mount. Reproducible test case (on a system with writable /etc/mtab): mount -o loop,ro /tmp/ro /mnt mount -t tmpfs tmpfs /mnt mount -o remount,ro /mnt cat /etc/mtab | tail -2 Signed-off-by: Valerie Aurora --- mount/fstab.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'mount/fstab.c') diff --git a/mount/fstab.c b/mount/fstab.c index 97d64a2c8..bfb2e5d35 100644 --- a/mount/fstab.c +++ b/mount/fstab.c @@ -215,6 +215,24 @@ getmntfile (const char *name) { return NULL; } +/* + * Given the name NAME, and the place MCPREV we found it last time, + * try to find it in mtab. + */ +struct mntentchn * +getmntfilebackward (const char *name, struct mntentchn *mcprev) { + struct mntentchn *mc, *mc0; + + mc0 = mtab_head(); + if (!mcprev) + mcprev = mc0; + for (mc = mcprev->prev; mc && mc != mc0; mc = mc->prev) + if (streq(mc->m.mnt_dir, name) || + streq(mc->m.mnt_fsname, name)) + return mc; + return NULL; +} + /* * Given the directory name NAME, and the place MCPREV we found it last time, * try to find more occurrences. -- cgit v1.2.3-55-g7522