Messages in this thread | | | From | "Peter T. Breuer" <> | Subject | how stop sync on last close of removable medium? | Date | Sat, 30 Sep 2006 05:15:34 +0200 (MET DST) |
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blkdev_close calls blkdev_put, which does a sync if we were the last opener of the device and are now closing:
if (!--bdev->bd_openers) { sync_blockdev(bdev); kill_bdev(bdev); }
This is bad news for nbd-like devices which use a client daemon to transfer data out of the device. If there are requests pending when the daemon is killed off (hey, we may want to shut down!) then the sync in the daemon's close of its device creates a deadlock. The sync will not complete until the daemon sends pending requests which it will not do since it is closing due to death.
Is there a mechanism to prevent this sync occuring? Say for removable devices?
(I don't see it, due to blindness and mental density ... I could change blkdev_close in inode->i_fops, I suppose, but that is attached to an inode, presumably of our special device node in the fs above, and by the time I get to it we have already opened the device node and it seems that changing the release method then doesn't actually do anything. Shrug).
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