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    SubjectRe: [PATCH] memory mapped files not updating timestamps
    On Wed, 2006-05-17 at 20:24 +0100, Hugh Dickins wrote:
    > On Wed, 17 May 2006, Peter Staubach wrote:

    > > The changes add support to detect when the modification time needs to be
    > > updated by placing a hook in __set_pages_dirty_buffers and
    > > __set_pages_dirty_nobuffers. One of these two routines will be invoked
    > > when the dirty bit is detected in the pte. The hook sets a new bit in the
    > > address_space mapping struct indicating that the file which is associated
    > > with that part of the address space needs to have its modification and
    > > change time attributes updated.
    > You're adding a little overhead to every set_page_dirty, when the vast
    > majority (ordinary writes) don't need it: their mctime update is already
    > well taken care of. (Or should we be deleting the code that does that?
    > I think I'd rather not dare.)

    It would make the code more symetric.

    > I think you'd do better to target those places where set_page_dirty is
    > called on a mapped page - and do the file_update_time at that point -
    > or as near to that point as is sensible/permitted given the locking
    > (vma->vm_file gives you the file without needing inode_update_time).

    > Peter Zijlstra has patches relating to dirty mmaps in the -mm tree
    > at present: I need to take a look at those, and I'll see if it would
    > make sense to factor in this mctime issue on top of those - you may
    > want to do the same.

    Look for the callsites of set_page_dirty_balance(), those two points are
    where writable file pages are dirtied.


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