On Mon, Feb 19, 2024 at 07:28:41PM -0800, Andrew Morton wrote: > On Tue, 20 Feb 2024 11:33:04 +0900 Byungchul Park <byungchul@xxxxxx> wrote: > > > > Yes, this changelog is missing rather a lot of important information. > > > > > > I pulled together the below, please check. > > > > To make it more clear, I need to explain it more. I posted the following > > two patches while resolving the oops issue. However, two are going on > > for different purposes. > > > > 1) https://lkml.kernel.org/r/20240219041920.1183-1-byungchul@xxxxxx > > > > I started this patch as the fix for the oops. However, I found the > > root cause comes from using -1 as an array index. So let the root > > cause fix go with another thread, 2). Nevertheless, 1) is still > > necessary as a *reasonable optimization* but not the real fix any > > more. > > Well I altered this patch's changelog to tell readers that it is an > optimization. But one does wonder why it isn't simply a bugfix. > Attempting to migrate to a memoryless node is clearly as error. I agree with what Oscar Salvador said: "As this is not a bug fix but an optimization, as we will fail anyways in migrate_misplaced_folio() when migrate_balanced_pgdat() notices that we do not have any memory on that node." https://lore.kernel.org/lkml/ZdG1yO29WTyRiw8Q@localhost.localdomain/ So assuming all the related code works correctly, the migration will safely fail even without this optimization patch. Byungchul > Presumably the called code handles it somehow, but in what fashion and > at what cost? > > > 2) https://lkml.kernel.org/r/20240216111502.79759-1-byungchul@xxxxxx > > > > I found the root cause of the oops comes from using -1 as an array > > index. So moved all the oops message, Fixes: tag, and cc stable to > > here. Long story short, 2) is the *real fix* for the oops. > >
