On 10/07/2013 04:14 PM, John Stultz wrote: >> >> I see from the change history of the patch that this was an madvise() at >> some point, but was changed into a separate system call at some point, >> does anyone remember why that was? A quick look through my LKML >> archives doesn't really make it clear. > > The reason we can't use madvise, is that to properly handle error cases > and report the pruge state, we need an extra argument. > > In much earlier versions, we just returned an error when setting > NONVOLATILE if the data was purged. However, since we have to possibly > do allocations when marking a range as non-volatile, we needed a way to > properly handle that allocation failing. We can't just return ENOMEM, as > we may have already marked purged memory as non-volatile. > > Thus, that's why with vrange, we return the number of bytes modified, > along with the purge state. That way, if an error does occur we can > return the purge state of the bytes successfully modified, and only > return an error if nothing was changed, much like when a write fails. > I am not clear at all what the "purge state" is in this case. -hpa -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>