From: Francis Moreau <francis.moro@gmail.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Dilger <adilger@sun.com>, linux-fsdevel@vger.kernel.org
Subject: Re: sys_umount() returns EBUSY when doing: sh -c "mount /dev/sdc1 /mnt; umount /mnt"
Date: Mon, 15 Mar 2010 21:23:02 +0100 [thread overview]
Message-ID: <38b2ab8a1003151323q6155e917ia74da84475db66f9@mail.gmail.com> (raw)
In-Reply-To: <20100315163454.GV30031@ZenIV.linux.org.uk>
On Mon, Mar 15, 2010 at 5:34 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Mon, Mar 15, 2010 at 10:04:46AM -0600, Andreas Dilger wrote:
>> On 2010-03-13, at 13:30, Francis Moreau wrote:
>> >I've some shell scripts which try to find out the filesystem hosted by
>> >a block device.
>> >
>> >They basically do this:
>> >
>> > mount /dev/sdc1 /mnt
>> > fs=$(stat -f -c %T $mount_point)
>> > umount /mnt
>>
>> Mounting an in-use filesystem is a bad idea.
>
> Huh? mount() will happily create another vfsmount refering to the same
> superblock in that case. It *is* OK to mount the same block device twice;
> any fs that uses get_sb_bdev() will DTRT.
>
> It should be safe. The lack of error checking after mount, OTOH, is not.
>
Well I omitted the error checking since it was not revelant in my
case: umount(8) fails but not mount(8).
--
Francis
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next prev parent reply other threads:[~2010-03-15 20:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <38b2ab8a1003130056u4b025839i556a797ccad894de@mail.gmail.com>
2010-03-13 20:30 ` sys_umount() returns EBUSY when doing: sh -c "mount /dev/sdc1 /mnt; umount /mnt" Francis Moreau
2010-03-15 16:04 ` Andreas Dilger
2010-03-15 16:34 ` Al Viro
2010-03-15 20:23 ` Francis Moreau [this message]
2010-03-16 6:53 ` Ian Kent
2010-03-15 20:19 ` Francis Moreau
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