On 2/5/25 09:47, Alistair Popple wrote:

FS DAX requires file systems to call into the DAX layout prior to unlinking
inodes to ensure there is no ongoing DMA or other remote access to the
direct mapped page. The fuse file system implements
fuse_dax_break_layouts() to do this which includes a comment indicating
that passing dmap_end == 0 leads to unmapping of the whole file.

However this is not true - passing dmap_end == 0 will not unmap anything
before dmap_start, and further more dax_layout_busy_page_range() will not
scan any of the range to see if there maybe ongoing DMA access to the
range. Fix this by passing -1 for dmap_end to fuse_dax_break_layouts()
which will invalidate the entire file range to
dax_layout_busy_page_range().

Signed-off-by: Alistair Popple <apopple@nvidia.com>
Co-developed-by: Dan Williams <redacted>
Signed-off-by: Dan Williams <redacted>
Fixes: 6ae330cad6ef ("virtiofs: serialize truncate/punch_hole and dax fault path")
Cc: Vivek Goyal <vgoyal@redhat.com>

Looks good

Reviewed-by: Balbir Singh <redacted>