Messages in this thread | | | Date | Tue, 24 Feb 2004 10:53:39 +1100 | From | Nathan Scott <> | Subject | Re: [PATCH] blkdev_open/bd_claim vs BLKBSZSET |
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On Mon, Feb 23, 2004 at 11:28:04PM +0000, viro@parcelfarce.linux.theplanet.co.uk wrote: > On Tue, Feb 24, 2004 at 10:17:05AM +1100, Nathan Scott wrote: > > Hi there, > > > > I was modifying mkfs.xfs to use O_EXCL for 2.6, and hit a snag. > > It seems that once I've opened a block dev with O_EXCL I can no > > longer issue the BLKBSZSET ioctl to it. (Is that the expected > > behavior? If so, ignore...) > > > And mkfs gets EBUSY back from the ioctl. Using the patch > > below, the ioctl succeeds cos the original filp bdev owner > > from open now matches with the owner in the ioctl call. I > > suspect that would be the correct behavior, but perhaps I'm > > overlooking some good reason for it being this way? > > <shrug> it can be done that way, but I really wonder why the hell does > mkfs.xfs bother with BLKBSZSET in the first place?
Thats taking me back a few years - IIRC this was originally added because mkfs.xfs zeroes out the last N KB of the device before it goes on to creating the XFS filesystem. Waaay back (~3 years now?) there was a problem when someone had, say, a 4K block size ext2 fs on the device - mount/unmount of that left the device block size at 4K in the kernel, when mkfs.xfs then came along it would not be able to zero the last small-amount-less-than-4K of the device (on devices where the size was not 4K aligned only - heh, that was a fun wrinkle) and mkfs would see write-past-end-of-device errors.
No idea if that can still happen in 2.6, I imagine it can in 2.4 where we originally saw the problem.
> FWIW, that ioctl is practically never the right thing to do these days. > I'm not saying that we shouldn't apply the patch - it looks sane - but > it looks like mkfs.xfs is doing something bogus.
At least for some older kernel versions this was needed - possibly still is, I'm not sure.
cheers.
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