On Thu, Dec 17, 2009 at 11:30:36AM -0500, tytso@xxxxxxx wrote: > That's because apparently the iSCSI and DMA blocks assume that they > have Real Pages (tm) passed to block I/O requests, and apparently XFS > ran into problems when sending vmalloc'ed pages. I don't know if this > is a problem if we pass the bio layer addresses coming from the SLAB > allocator, but oral tradition seems to indicate this is problematic, > although no one has given me the full chapter and verse explanation > about why this is so. Actually at least iscsi now has a workaround for that by checking for PageSlab. Back when we deal with the XFS issue that check was only available with debug options enabled. I tried to sort it out by agreeing with the block and iscsi folks that either a) we need to send down refcountable pages b) block drivers need to accept kmalloced pages I could not get any afreement, and thus we stopped using the kmalloced pages in XFS which was easy enough. A bit later people fixed iscsi, but we still don't have formal rules about what is acceptable to the block layer. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html