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    SubjectRe: [PATCH][RFC] fast file mapping for loop
    On Wed, Jan 09 2008, Andi Kleen wrote:
    > Jens Axboe <> writes:
    > >
    > > So how does it work? Instead of punting IO to a thread and passing it
    > > through the page cache, we instead attempt to send the IO directly to the
    > Great -- something like this was needed for a long time.
    > > - The file block mappings must not change while loop is using the file.
    > > This means that we have to ensure exclusive access to the file and
    > > this is the bit that is currently missing in the implementation. It
    > > would be nice if we could just do this via open(), ideas welcome...
    > get_write_access()/put_write_access() will block other writers.
    > But as pointed out by others that is not enough for this.

    Yeah, basically allowing O_RDONLY | O_DIRECT opens should be ok, but we
    can't allow writes and we can't allow page cache to exist for this file
    outside of loop.

    > I suppose you could use a white list like a special flag for file systems
    > (like ext2/ext3) that do not reallocate blocks.

    Irk, but yeah we probably need something like that for now until Chris
    proposes his API addition.

    Jens Axboe

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      Last update: 2008-01-10 09:47    [W:0.020 / U:0.636 seconds]
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