On Tue, 2 Apr 2013, Minchan Kim wrote: > On Fri, Mar 29, 2013 at 01:01:14PM -0700, Hugh Dickins wrote: > > On Fri, 29 Mar 2013, Minchan Kim wrote: > > > On Thu, Mar 28, 2013 at 11:19:12AM -0700, Dan Magenheimer wrote: > > > > > > > > I wonder if something like this would have a similar result for zram? > > > > (Completely untested... snippet stolen from swap_entry_free with > > > > SetPageDirty added... doesn't compile yet, but should give you the idea.) > > > > Be careful, although Dan is right that something like this can be > > done for zram, I believe you will find that it needs a little more: > > either a separate new entry point (not my preference) or a flags arg > > (or boolean) added to swap_slot_free_notify. > > > > Because this is a different operation: end_swap_bio_read() wants > > to free up zram's compressed copy of the page, but the swp_entry_t > > must remain valid until swap_entry_free() can clear up the rest. > > Precisely how much of the work each should do, you will discover. > > First of all, Thanks for noticing it for me! > > If I parse your concern correctly, you are concerning about > different semantic on two functions. > (end_swap_bio_read's swap_slot_free_notify VS swap_entry_free's one). > > But current implementatoin on zram_slot_free_notify could cover both cases > properly with luck. > > zram_free_page caused by end_swap_bio_read will free compressed copy > of the page and zram_free_page caused by swap_entry_free later won't find > right index from zram->table and just return. > So I think there is no problem. > > Remained problem is zram->stats.notify_free, which could be counted > redundantly but not sure it's valuable to count exactly. > > If I miss your point, please pinpoint your concern. :) Looking at it again, I do believe you and Dan are perfectly correct, and I was again the confused one. Though I'd be happier if I could see just how I was misreading it: makes me wonder if I had a great insight that I can no longer grasp hold of! I think I was paranoid about a swp_entry_t getting recycled prematurely: but swap_entry_free remains in control of that - freeing a swap entry is no part of what notify_free gets up to. Sorry for wasting your time. Hugh -- 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>