On Wed, Jun 05, 2024 at 01:29:29PM -0600, Martin Oliveira wrote: > The standard kernfs vm_ops installs a page_mkwrite() operator which > modifies the file update time on write. > > This not always required (or makes sense), such as in the P2PDMA, which s/This/This is/ ? > uses the sysfs file as an allocator from userspace. > > Furthermore, having the page_mkwrite() operator causes > writable_file_mapping_allowed() to fail due to > vma_needs_dirty_tracking() on the gup flow, which is a pre-requisite for > enabling P2PDMA over RDMA. > > Fix this by adding a new boolean on kernfs_ops to differentiate between > the different behaviours. > + * Use the file as an allocator from userspace. This disables > + * page_mkwrite() to prevent the file time from being updated on write > + * which enables using GUP with FOLL_LONGTERM with memory that's been > + * mmaped. "mmaped" does seem more commonly used in Linux than "mmapped", but the base word "mapped" definitely requires "pp", so "mmaped" looks funny to me.
