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

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On 2/1/24 09:45, Miklos Szeredi wrote:
On Thu, 1 Feb 2024 at 00:09, Bernd Schubert <bschubert@xxxxxxx> 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.

I tested with xfstest, but not with fsx yet. I can look into that. Do you have by any chance an exact command I should run?


Thanks,
Bernd




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