On Thu, 2011-05-19 at 16:24 -0500, Christoph Lameter wrote: > On Thu, 19 May 2011, J Freyensee wrote: > > > On Thu, 2011-05-19 at 15:51 -0500, Christoph Lameter wrote: > > > On Thu, 19 May 2011, james_p_freyensee@xxxxxxxxxxxxxxx wrote: > > > > > > > From: J Freyensee <james_p_freyensee@xxxxxxxxxxxxxxx> > > > > > > > > Currently, kmalloc_index() can return -1, which can be > > > > passed right to the kmalloc_caches[] array, cause a > > > > > > No kmalloc_index() cannot return -1 for the use case that you are > > > considering here. The value passed as a size to > > > kmalloc_slab is bounded by 2 * PAGE_SIZE and kmalloc_slab will only return > > > -1 for sizes > 4M. So we will have to get machines with page sizes > 2M > > > before this can be triggered. > > > > > > > > > > Okay. I thought it would still be good to check for -1 anyways, even if > > machines today cannot go above 2M page sizes. I would think it would be > > better for software code to always make sure a case that this could > > never happen instead of relying on whatever physical hardware limits the > > linux kernel could be running on on today's machines or future machines, > > because technology has shown limits can change. I would think > > regardless what this code runs on, this is still a software flaw that > > can be considered not a good thing to allow lying around in software > > code that can easily be fixed. > > This is basically macro style code that is mostly folded at compile time > and we have to obey certain restrictions to convince the compiler to > properly do that. Took us a long time to get that right. > > Not sure what to do instead of returning -1 in kmalloc_slab. I think returning -1 is fine; I just think code using the function should be checking for it and protect itself for errors in kernel space. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>