On Tue, Jun 23, 2020 at 8:21 AM Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > The page faultround path ->map_pages is implemented in XFS via > filemap_map_pages(). This function checks that pages found in page > cache lookups have not raced with truncate based invalidation by > checking page->mapping is correct and page->index is within EOF. > > However, we've known for a long time that this is not sufficient to > protect against races with invalidations done by operations that do > not change EOF. e.g. hole punching and other fallocate() based > direct extent manipulations. The way we protect against these > races is we wrap the page fault operations in a XFS_MMAPLOCK_SHARED > lock so they serialise against fallocate and truncate before calling > into the filemap function that processes the fault. > > Do the same for XFS's ->map_pages implementation to close this > potential data corruption issue. > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx> I wonder... should xfs_file_fadvise(POSIX_FADV_WILLNEED) also be taking XFS_MMAPLOCK_SHARED instead of XFS_IOLOCK_SHARED? Not that it matters that much? Thanks, Amir.
