On 05.08.22 08:29, Alistair Popple wrote: > When pinning pages with FOLL_LONGTERM check_and_migrate_movable_pages() > is called to migrate pages out of zones which should not contain any > longterm pinned pages. > > When migration succeeds all pages will have been unpinned so pinning > needs to be retried. Migration can also fail, in which case the pages > will also have been unpinned but the operation should not be retried. If > all pages are in the correct zone nothing will be unpinned and no retry > is required. > > The logic in check_and_migrate_movable_pages() tracks unnecessary state > and the return codes for each case are difficult to follow. Refactor the > code to clean this up. No behaviour change is intended. > > Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx> > > --- > > Changes for v2: > > - Split into different functions as suggested by John. > - Made error handling more conventional as requested by Jason. > > Personally I'm not entirely convinced the conventional approach to error > handling is easier to follow here but have left it in for feedback as I > might be getting too familiar with the code. > > Originally posted as "mm/gup.c: Simplify and fix > check_and_migrate_movable_pages() return codes"[1]. > > Changes from that version: > > - Restore the original isolation failure behaviour and don't fail the > pup. Instead retry indefinitely. > - Unpin all pages on retry or failure rather than just failure. > > [1] https://lore.kernel.org/linux-mm/814dee5d3aadd38c3370eaaf438ba7eee9bf9d2b.1659399696.git-series.apopple@xxxxxxxxxx/ > --- > mm/gup.c | 159 ++++++++++++++++++++++++++++++-------------------------- > 1 file changed, 88 insertions(+), 71 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index e26ccc0..60cb30a 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1900,20 +1900,14 @@ struct page *get_dump_page(unsigned long addr) > #endif /* CONFIG_ELF_CORE */ > > #ifdef CONFIG_MIGRATION > -/* > - * Check whether all pages are pinnable, if so return number of pages. If some > - * pages are not pinnable, migrate them, and unpin all pages. Return zero if > - * pages were migrated, or if some pages were not successfully isolated. > - * Return negative error if migration fails. > - */ > -static long check_and_migrate_movable_pages(unsigned long nr_pages, > - struct page **pages) > +static int collect_unpinnable_pages(struct list_head *movable_page_list, If we're already renaming stuff, can we make it clearer, that we are dealing with *longterm* unpinnable pages? -- Thanks, David / dhildenb
