lkml.org 
[lkml]   [1999]   [Nov]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: FIBMAP ioctl restrictions: why?
Alan Cox wrote:
> > While we're here, I would like to request FIBMAP on directories, thanks.
>
> Just fix all of the race conditions with ftruncate, the sanity checking
> and other missing map checks in the fs layers and send me a diff 8)

The result of FIBMAP can always be out of date by the time it reaches
user space. So you can only use it as a hint for optimising read order,
or like Lilo, you have to assume the underlying file is not being
changed.

If you use it as a hint there's no big deal if the information is
occasionally wrong due to a race. Are there any real race conditions
with FIBMAP that cause real problems?

(It's not a great hint for a lot of reasons. One of them is the
filesystem's tendancy to read ahead in a file, which tends to break your
carefully planned read sequence...)

-- Jamie

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:54    [W:0.049 / U:0.512 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site