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    SubjectRe: [parisc-linux] Re: Problems with kernel mmap (failing tst-mmap-eofsync in glibc on parisc)
    On 22 Aug 2003 13:56:06 -0500
    James Bottomley <James.Bottomley@SteelEye.com> wrote:

    > On Fri, 2003-08-22 at 13:31, David S. Miller wrote:
    > > On Fri, 22 Aug 2003 19:34:41 +0100 (BST)
    > > Hugh Dickins <hugh@veritas.com> wrote:
    > >
    > > > And to me. If VM_SHARED is set, then __vma_link_file puts the vma on
    > > > on i_mmap_shared. If VM_SHARED is not set, it puts the vma on i_mmap.
    > > > flush_dcache_page treats i_mmap_shared and i_mmap lists equally.
    > >
    > > But file system page cache writes only call flush_dache_page()
    > > if the page has a non-empty i_mmap_shared list.
    >
    > Hmm, but if it does that then the glibc bug test should show up on sparc
    > because the i_mmap_shared list is empty if we only do MAP_SHARED of read
    > only files.

    Sparc64's alias'able caches are 1) write-through and 2) quite small.

    I think I begin to see the issue clearly now.

    But you cannot do the VM_SHARED change without an audit first.
    Lots of code thinks that VM_SHARED means someone maybe wrote
    to the page through a mmap(). For example look at how filemap
    sync interprets this flag bit.
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