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umount: always use umount2 syscall with specified flags 

Make umount -f more compatible with util-linux 2.22.2.

Before:
  * 'umount -f': calls umount syscall,
        if it fails calls umount2 with 'MNT_FORCE'
  * 'mount -f -l': calls umount syscall,
        if it fails calls umount2 with 'MNT_LAZY'. 'MNT_FORCE' dropped
After:
  * 'umount -f': calls umount2 syscall with 'MNT_FORCE'
  * 'mount -f -l': calls umount2 syscall with 'MNT_LAZY' and 'MNT_FORCE'

function                                             old     new   delta
umount                                                45       -     -45
umount_main                                          610     555     -55

Signed-off-by: Anton Bondarenko <anton.bondarenko@axis.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2015-10-01 18:50:06 +02:00
parent c65a7596df
commit c919d561ad
1 changed files with 16 additions and 4 deletions
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20
util-linux/umount.c
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@ -81,8 +81,13 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
argv += optind;
// MNT_FORCE and MNT_DETACH (from linux/fs.h) must match
// OPT_FORCE and OPT_LAZY, otherwise this trick won't work:
doForce = MAX((opt & OPT_FORCE), (opt & OPT_LAZY));
// OPT_FORCE and OPT_LAZY.
{
typedef char bug[
(OPT_FORCE != MNT_FORCE || OPT_LAZY != MNT_DETACH) ? -1 : 1
];
}
doForce = opt & (OPT_FORCE|OPT_LAZY);
/* Get a list of mount points from mtab. We read them all in now mostly
* for umount -a (so we don't have to worry about the list changing while
@ -147,11 +152,18 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
// umount the directory even if we were given the block device.
if (m) zapit = m->dir;
// umount from util-linux 2.22.2 does not do this:
// umount -f uses umount2(MNT_FORCE) immediately,
// not trying umount() first.
// (Strangely, umount -fl ignores -f: it is equivalent to umount -l.
// We do pass both flags in this case)
#if 0
// Let's ask the thing nicely to unmount.
curstat = umount(zapit);
// Force the unmount, if necessary.
// Unmount with force and/or lazy flags, if necessary.
if (curstat && doForce)
#endif
curstat = umount2(zapit, doForce);
// If still can't umount, maybe remount read-only?
@ -168,7 +180,7 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
bb_error_msg(msg, m->device);
} else {
status = EXIT_FAILURE;
bb_perror_msg("can't %sumount %s", (doForce ? "forcibly " : ""), zapit);
bb_perror_msg("can't unmount %s", zapit);
}
} else {
// De-allocate the loop device. This ioctl should be ignored on