On Sun, 24 February 2008 18:57:32 +0800, David Woodhouse wrote: > On Sun, 2008-02-24 at 07:57 +0100, Jörn Engel wrote: > > Could a naïve implementation of this get exploited by doing a large > > number of truncates that just shave single bytes off various files? > > Yeah, which is why _my_ naïve implementation would do it for > truncate-to-zero instead of just _any_ truncate (which could even be > truncate-to-larger).
Truncate-to-larger is trivial to check. Almost every filesystem does it somewhere, including JFFS2. ;) But yeah, truncate-to-zero should catch the common case. > If allowing only truncate-to-zero isn't good enough, perhaps we could > allow truncation to use the ALLOC_DELETION pool when it's going to > obsolete at least one full data node. That's not so hard to check. I would simply always write out a "full" replacement node, i.e. the complete tail page for the file. No need to check if an old node gets obsoleted, we just made sure it does. Anyway, it is your baby, so you get to change the dirty diapers and pick your favorite pair of clean ones. Jörn -- Joern's library part 3: http://inst.eecs.berkeley.edu/~cs152/fa05/handouts/clark-test.pdf -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
