On Mon, 3 Feb 2014, Andrew Morton wrote: > On Mon, 3 Feb 2014 15:23:40 -0800 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Mon, 27 Jan 2014 18:03:04 +0800 Weijie Yang <weijie.yang@xxxxxxxxxxx> wrote: > > > > > swapoff clear swap_info's SWP_USED flag prematurely and free its resources > > > after that. A concurrent swapon will reuse this swap_info while its previous > > > resources are not cleared completely. > > > > > > These late freed resources are: > > > - p->percpu_cluster > > > - swap_cgroup_ctrl[type] > > > - block_device setting > > > - inode->i_flags &= ~S_SWAPFILE > > > > > > This patch clear SWP_USED flag after all its resources freed, so that swapon > > > can reuse this swap_info by alloc_swap_info() safely. > > > > > > This patch is just for a rare scenario, aim to correct of code. > > > > I believe that > > http://ozlabs.org/~akpm/mmots/broken-out/mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch > > makes this patch redundant? > > > > oop, hang on. This patch *is* a stealth-updated version of > http://ozlabs.org/~akpm/mmots/broken-out/mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch. > > Undocumented removals of si->swap_map have been added. What's going on > there? > > I think I'll stick with the original patch for now. If you see > additional optimisations or changes, let's address that separately? Correct decision, thanks: I explained in an answer when Acking the previous version why I dislike this version (it would prevent you from watching the slow progress of swapoff). 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>