On Mon, 14 Feb 2011 16:44:30 +0100 Tejun Heo <tj@xxxxxxxxxx> wrote: > Hello, > > On Mon, Feb 14, 2011 at 03:23:20PM +0100, Milan Broz wrote: > > >> I am not sure if this is complete fix... note that: > > >> - what happens during mirror resync and read-only log? > > >> - for COW, it there situation we need to update header in read-oly mode? (invalidated snap?) > > > > > > But if the underlying device is marked ro, dm shouldn't update it at > > > all. The device should be opened ro and ro policy should be enforced. > > > > Sure. So we need to check these situations I described. > > Yeap, it seems dm folks are gonna take care of dm part. > > > Btw the same pattern is in MD code in lock_rdev() ... > > Indeed, cc'ing Neil. Hi, the whole thread can be read from the > following URL. > > http://thread.gmane.org/gmane.linux.kernel/1099399/focus=1099735 > > blkdev_get() now rejects rw open of devices which are marked > read-only. I think the right thing to do would be opening the member > devices ro if the array is assembled for ro access (similar to Milan's > patch for dm). How does that sound? > > Thanks. > Sounds sensible ... though it is not all that easy to assemble an array as 'read-only'.... it is possible though. When the array is switched to read-write, do I have to call blkdev_get again asking for rw access, then close the old blkdev, or can I 'upgrade'? If a device has multiple opens: some read-only and some read-write, can I find out when the last read-write close is gone? That would be really useful, especially if a filesystem down-graded its open to read-only when it is remounted read-only.. [[And if filesystems could be convinced to open the device read-only when the fs is mounted read-only (and just do journal replay to internal data structures) that would be really awesome!!]] NeilBrown -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
