On Fri, Dec 09, 2022 at 09:19:37AM +0000, Akira Naribayashi (Fujitsu) wrote: > On Wed, 23 Nov 2022 10:26:05 +0000, Mei Gorman wrote: > > On Wed, Nov 09, 2022 at 05:41:12AM +0000, Akira Naribayashi (Fujitsu) wrote: > > > On Mon, 7 Nov 2022 15:43:56 +0000, Mei Gorman wrote: > > > > On Mon, Nov 07, 2022 at 12:32:34PM +0000, Akira Naribayashi (Fujitsu) wrote: > > > > > > Under what circumstances will this panic occur? I assume those > > > > > > circumstnces are pretty rare, give that 6e2b7044c1992 was nearly two > > > > > > years ago. > > > > > > > > > > > > Did you consider the desirability of backporting this fix into earlier > > > > > > kernels? > > > > > > > > > > > > > > > Panic can occur on systems with multiple zones in a single pageblock. > > > > > > > > > > > > > Please provide an example of the panic and the zoneinfo. > > > > > > This issue is occurring in our customer's environment and cannot > > > be shared publicly as it contains customer information. > > > Also, the panic is occurring with the kernel in RHEL and may not > > > panic with Upstream's community kernel. > > > In other words, it is possible to panic on older kernels. > > > I think this fix should be backported to stable kernel series. > > > > > > > > The reason it is rare is that it only happens in special configurations. > > > > > > > > How is this special configuration created? > > > > > > This is the case when the node boundary is not aligned to pageblock boundary. > > > > In that case, does this work to avoid rescanning an area that was already > > isolated? > > In the case of your patch, I think I need to clamp the isolated_end as well. > Because sometimes isolated_end < start_pfn(value before entering Scan after) < end_pfn. > > After re-reading the source, I think the problem is that min_pfn and low_pfn > can be out of range in fast_isolate_freepages. > How about the following patch? > Ok, makes sense and it is a condition that could happen because of pageblock alignment. -- Mel Gorman SUSE Labs
