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    SubjectRe: O_DIRECT
    On Tue, 20 Jul 2004 10:27:57 -0700
    Shesha Sreenivasamurthy <> wrote:

    Hi Shesha,

    > I am having trouble with O_DIRECT. Trying to read or write from a block
    > device partition.
    > 1. Can O_DIRECT be used on a plain block device partition say
    > "/dev/sda11" without having a filesystem on it.


    > 2. If no file system is created then what should be the softblock size.
    > I am using the IOCTL "BLKBSZGET". Is this correct?


    > 3. Can we use SEEK_END with O_DIRECT on a partition without filesystem.


    I'm using these exact things in an application.

    Note that with 2.4 kernels the "granularity" you can use for offset
    and r/w size is the softblock size (*). For 2.6 the requirements are
    much more relaxed: it's the device blocksize (typically 512 byte).

    (*): actually one of offset or r/w size has a smaller minimum if
    I remember correctly. Don't remember which one. But if you assume
    the softblock size as a minimum for both you're allways safe.

    Rob van Nieuwkerk
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