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    SubjectRe: [PATCH] update ctime and mtime for mmaped write
    Miklos Szeredi wrote:
    >>> Inspired by Peter Staubach's patch and the resulting comments.
    >> An updated version of the original patch was submitted to LKML
    >> yesterday... :-)
    > Strange coincidence :)
    >>> file = vma->vm_file;
    >>> start = vma->vm_end;
    >>> + mapping_update_time(file);
    >>> if ((flags & MS_SYNC) && file &&
    >>> (vma->vm_flags & VM_SHARED)) {
    >>> get_file(file);
    >> It seems to me that this might lead to file times being updated for
    >> non-MAP_SHARED mappings.
    > In theory no, because the COW-ed pages become anonymous and are not
    > part of the original mapping any more.

    I must profess to having a incomplete understanding of all of this
    support, but then why would it be necessary to test VM_SHARED at
    this point in msync()?

    I ran into problems early on with file times being updated incorrectly
    so I am a little sensitive this aspect.

    >>> +int set_page_dirty_mapping(struct page *page);
    >> This aspect of the design seems intrusive to me. I didn't see a strong
    >> reason to introduce new versions of many of the routines just to handle
    >> these semantics. What motivated this part of your design? Why the new
    >> _mapping versions of routines?
    > Because there's no way to know inside the set_page_dirty() functions
    > if the dirtying comes from a memory mapping or from a modification
    > through a normal write(). And they have different semantics, for
    > write() the modification times are updated immediately.

    Perhaps I didn't understand what page_mapped() does, but it does seem to
    have the right semantics as far as I could see.


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      Last update: 2007-02-21 19:59    [W:0.025 / U:4.144 seconds]
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