On Thu, Dec 17, 2009 at 12:10:25PM -0500, Christoph Hellwig wrote: > 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. It would be good to get some formal rules articulated. Someone has asserted that the AoE (ATA over Ethernet) driver will barf on SLAB/kmalloc allocated memory. True, false? - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
