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Re: SPARSE files considered harmful - please revert
On Mon, May 19, 2003 at 03:47:32PM +0100, Max Bowsher wrote:
> Bill C. Riemers wrote:
> > Only executable files should be sparse files... Under Linux, the
> executable
> > bit is checked by cp. (Or at least this was true several years ago, when
> I
> > last looked at the code.) Only if the file is marked as executable is it
> > possibly made sparse.
>
> I haven't looked in the code, but there is absolutely no mention of this in
> the man page.
... and the non-executable file /var/log/lastlog can cause big trouble if it
isn't sparse.
> > Granted sometimes you do have a data file which can be made sparse.
> > However, unless you are familiar with the code used to read the file, this
> > is very dangerous. So this should be decided on a case by case basis.
>
> Um? By my understanding, making a file sparse can never be dangerous. It can
> cause sub-optimal performance, but code reading the file doesn't have to be
> aware of anything special - the OS takes care of it.
>
Agree. Something along the lines of Martin Buchholz's suggestion makes sense:
make the file sparse when writing after a seek past the end of file.
There is already support to detect that condition, to handle the win95 lseek
bug.
Pierre
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