Re: [PATCH v2 1/5] fuse: Fix VM_MAYSHARE and direct_io_allow_mmap

On Thu, 1 Feb 2024 at 00:09, Bernd Schubert bschubert@ddn.com wrote:

There were multiple issues with direct_io_allow_mmap:

• fuse_link_write_file() was missing, resulting in warnings in fuse_write_file_get() and EIO from msync()
• "vma->vm_ops = &fuse_file_vm_ops" was not set, but especially fuse_page_mkwrite is needed.

The semantics of invalidate_inode_pages2() is so far not clearly defined in fuse_file_mmap. It dates back to commit 3121bfe76311 ("fuse: fix "direct_io" private mmap") Though, as direct_io_allow_mmap is a new feature, that was for MAP_PRIVATE only. As invalidate_inode_pages2() is calling into fuse_launder_folio() and writes out dirty pages, it should be safe to call invalidate_inode_pages2 for MAP_PRIVATE and MAP_SHARED as well.

Did you test with fsx (various versions can be found in LTP/xfstests)? It's very good at finding mapped vs. non-mapped bugs.

Thanks, Miklos