Date: Tue, 22 Aug 1995 16:26:25 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: terry@cs.weber.edu (Terry Lambert) Cc: hackers@freebsd.org Subject: Using space in a DOS filesystem Message-ID: <199508220656.QAA25934@genesis.atrad.adelaide.edu.au> In-Reply-To: <9508220320.AA28296@cs.weber.edu> from "Terry Lambert" at Aug 21, 95 09:20:03 pm
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Terry Lambert stands accused of saying: > Probably your pseudo-device needs to: > > 1) Look up the file > 2) Assert a mandatory file lock Instructions on this one would be needed 8) > 3) Verify that the file is in fact contiguous > 4) Export as device node that is an alias for the device node > the file system is actually on, with the addition of a sector > bias and a length (both derived from the underlying file system). > > This could probably be rolled into vnconfig, but implies a logical to Not for the desired purpose, see my recent posts on this thread. > physical address translation is possible (you might have to add one > as a file system specific ioctl()), and a contiguity check is also > possible (perhaps by traversing the block offsets linearly by using > an additional "offset" argument to the ioctl() above, or with the > addition of another ioctl()). Then you'd flag the vnconfig'ed device > for physical rather than logical I/O. Checking for contiguity is relatively trivial given the nature of the FAT filesystem; all this sort of 'health checking' can be easily included in the "do we accept this slab" tests. The issues that I can't resolve at this point are : 1) Keeping everyone else's grubby mitts off the file. 2) Exporting a device/devices that represent the filesystem(s) inside the slab. > Terry Lambert -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] My car has "demand start" -Terry Lambert UNIX: live FreeBSD or die! [[
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