Subject: Re: problem with tmpfs and linux emulation?
To: Andrew Reilly <firstname.lastname@example.org>
From: Steven M. Bellovin <email@example.com>
Date: 11/14/2005 19:31:14
In message <20051114233622.GA12603@gurney.reilly.home>, Andrew Reilly writes:
>On Sun, Nov 13, 2005 at 07:49:38PM -0500, Steven M. Bellovin wrote:
>> It seems likely that nothing will make this work short of a real byte
>> offset in d_off. This in turn suggests that either the linux emulation
>> layer has to have a way of knowing if it needs to do a conversion, or
>> the file system layer needs to do the conversion, possibly as a result
>> of a mount-time flag. I'd really rather avoid the latter if possible
>> -- how expensive would it be for tmpfs to maintain a real byte count?
>> (Seeking to that point need not be cheap; it's an infrequent operation,
>> I suspect.)
>Is it not possible to have the emulated lseek understand the
>opaque cookies (perhaps with a hash lookup) and do the right
I haven't looked at the code, but I suspect that that doesn't work well
-- when do you purge the table?
>What is the good of passing an opaque cookie out to user-land if
>it's not subsequently useful for something?
Good question, unless it's the sort of cookie used by telldir()/
--Steven M. Bellovin, http://www.cs.columbia.edu/~smb