On 13:52 Thu 16 May , Dave Chinner wrote: > On Thu, May 16, 2013 at 10:42:16AM +0200, Oskar Andero wrote: > > The shrinkers must return -1 to indicate that it is busy. Instead, treat > > any negative value as busy. > > Why? The API defines return condition for aborting a scan and gives > a specific value for doing that. i.e. explain why should change the > API to over-specify the 'abort scan" return value like this. As I pointed out earlier, looking in to the code (from master): if (shrink_ret == -1) break; if (shrink_ret < nr_before) ret += nr_before - shrink_ret; This piece of code lacks a sanity check and will only function if shrink_ret is either greater than zero or exactly -1. If shrink_ret is e.g. -2 this will lead to undefined behaviour. > FWIW, using "any" negative number for "abort scan" is a bad API > design decision. It means that in future we can't introduce > different negative return values in the API if we have a new to. > i.e. each specific negative return value needs to have the potential > for defining a different behaviour. An alternative to my patch would be to add: if (shrink_ret < -1) /* handle illegal return code in some way */ > So if any change needs to be made, it is to change the -1 return > value to an enum and have the shrinkers return that enum when they > want an abort. I am all for an enum, but I still believe we should handle the case where the shrinkers return something wicked. -Oskar -- 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>