Re: [NFS] [PATCH] mmap corruption

[Trond Myklebust <trond.myklebust@fys.uio.no>]

>>>>> " " == Steve Dickson <SteveD@redhat.com> writes:

     > The Cause: Memory mapped pages were not being flushed out in a
     > timely manner. When a file is about to truncated (up or down),
     > nfs_writepage() is called (by filemap_fdatasync()) to flush out
     > dirty pages. When this done asynchronously, nfs_writepage()
     > will (indirectly) call nfs_strategy().  nfs_strategy() wants to
     > send groups of pages (in this case 4 pages). Now in the error
     > case, only one page was dirty so it was *not* flushed out.
     > Eventually that page would be flushed (by kupdate) but it was
     > too late because the file size had already change due to a
     > second truncation.

That simply doesn't ring true. The nfs_wb_all() immediately after the
call to filemap_fdatasync() should ensure that *all* scheduled writes
will flushed out.

Cheers,
  Trond