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    SubjectRe: [PATCH] aio: propogate post-EIOCBQUEUED errors to completion event
    On Tue, 2007-02-20 at 10:40 -0800, Zach Brown wrote:
    > >> There are some strange O_DIRECT corner cases in here such that the
    > >> 'last
    > >> writer' may actually be a 'last reader' and winning can mean have
    > >> a copy
    > >> of the page in page cache older than the copy on disk.
    > >
    > > As long as it is marked dirty so that it eventually gets synced to
    > > disk,
    > > it shouldn't matter.
    > No, Chris is pointing out that an an O_DIRECT write can leave clean
    > read pages in the page cache.
    > All it takes is giving a source buffer for the write which is an mmap
    > ()ed apeture of the region that is being written to. If you get the
    > offsets right you can get the get_user_pages() down in fs/direct-io.c
    > will populate the page cache before the actual O_DIRECT write gets to
    > it.

    With invalidate_inode_pages2()? That is supposed to wait until the page
    lock is taken -> read is done. It then calls unmap_mapping_range() which
    will remove the offending page from any existing mappings. Sure an
    application could get stale data, but if it is reading while an O_DIRECT
    write is proceeding, then it gets what it deserves.


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      Last update: 2007-02-21 01:09    [W:0.020 / U:158.320 seconds]
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