Messages in this thread | | | Date | Wed, 7 Aug 2002 22:55:42 +0200 | From | Lars Ellenberg <> | Subject | Re: stacked bdev driver, howto? locking of lower level block device |
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ok, I got some answers. not that much though.
On Mon, Aug 05, 2002 at 10:16:52PM +0200, I wrote: > I'd like to implement some kind of locking of the lower level > block device, so nobody can mount it/modify it underneath the drbd > driver. > > I know drivers/md/md.c does this somehow. I tried to understand > and adapt, but it does not work. to be more explicit: /* * prevent the device from being mounted, repartitioned or * otherwise reused by a RAID array (or any other kernel * subsystem), by opening the device. [simply getting an * inode is not enough, the SCSI module usage code needs * an explicit open() on the device] */ static int lock_rdev(mdk_rdev_t *rdev)
but this does _not_ prevent the device from being mounted or used, I did not check the repartitioning.
On Tue, Aug 06, 2002 at 12:42:38AM -0500, Milton Miller suggested: >> In 2.5 see bd_claim and bd_release in fs/block_dev.c well, I need to have this on 2.4 for now. I did not check the 2.5 code yet. other opinions whether this will work when we swithc to 2.5?
>> In 2.4 as fars as I know you have to add yourself to the list of checks >> that are incomplete and don't all check against each other (swap, >> filesystems, raid, etc). could someone be so kind an be more explicit please. what piece of code do "list of checks" translate to?
or do I have to follow this? On Wed, Aug 07, 2002 at 10:51:00AM -0700, Tim Pepper had the impression: >> this is not possible from what I've seen inside the kernel. You can >> do a bdget/blkdev_get() on teh underlying dev, but as far as I saw >> that only prevents somebody from fdisking the device. >> >> I think a lot of people figure this is just in line with the unix way >> of allowing you to shoot yourself in the foot if you want. I don't >> have a big problem with that, but understand the arguments to the >> contrary. is this the case? it is not possible? I understand that all this is not that important, but I want do do it anyways, to reduce the careless foot shooter. I suppose, iff someone really wants to, the shooting can be done with raw io anyways. no problem, then every now and then someone will have to do some transplantation...
BTW: why can I mount just about every device multiple times on different mountpoints at the same time?
ok, my questions remain: > > - How does block device locking work? > - In which mode do I have to open it? > - Which flags have to be set? > - What else am I missing?
Thanks. Lars-Gunnar - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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