On Thu, 17 Sep 2020, Dave Chinner wrote: > > So.... > > P0 p1 > > hole punch starts > takes XFS_MMAPLOCK_EXCL > truncate_pagecache_range() > unmap_mapping_range(start, end) > <clears ptes> > <read fault> > do_fault_around() > ->map_pages > filemap_map_pages() > page mapping valid, > page is up to date > maps PTEs > <fault done> > truncate_inode_pages_range() > truncate_cleanup_page(page) > invalidates page > delete_from_page_cache_batch(page) > frees page > <pte now points to a freed page> No. filemap_map_pages() checks page->mapping after trylock_page(), before setting up the pte; and truncate_cleanup_page() does a one-page unmap_mapping_range() if page_mapped(), while holding page lock. (Of course, there's a different thread, in which less reliance on page lock is being discussed, but that would be a future thing.) Hugh
