Hi, Gregory, Gregory Price <gourry@xxxxxxxxxx> writes: > To migrate unmapped pagecache folios, migrate_misplaced_folio and > migrate_misplaced_folio_prepare must handle folios without VMAs. IMHO, it's better to use migrate_misplaced_folio() instead of migrate_misplaced_folio for readability in patch title and description. > migrate_misplaced_folio_prepare checks VMA for exec bits, so allow > a NULL VMA when it does not have a mapping. > > migrate_misplaced_folio must call migrate_pages with MIGRATE_SYNC > when in the pagecache path because it is a synchronous context. I don't find the corresponding implementation for this. And, I don't think it's a good idea to change from MIGRATE_ASYNC to MIGRATE_SYNC. This may cause too long page access latency for page placement optimization. The downside may offset the benefit. And, it appears that we can delete the "vma" parameter of migrate_misplaced_folio() because it's not used now. This is a trivial code cleanup. > Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx> > Signed-off-by: Gregory Price <gourry@xxxxxxxxxx> > --- > mm/migrate.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index dfb5eba3c522..3b0bd3f21ac3 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -2632,7 +2632,7 @@ int migrate_misplaced_folio_prepare(struct folio *folio, > * See folio_likely_mapped_shared() on possible imprecision > * when we cannot easily detect if a folio is shared. > */ > - if ((vma->vm_flags & VM_EXEC) && > + if (vma && (vma->vm_flags & VM_EXEC) && > folio_likely_mapped_shared(folio)) > return -EACCES; --- Best Regards, Huang, Ying
