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    SubjectRe: A problem about DIRECT IO on ext3


    --- li nux <lnxluv@yahoo.com> wrote:

    >
    >
    > --- Jens Axboe <axboe@suse.de> wrote:
    >
    > > On Mon, Aug 29 2005, Erik Mouw wrote:
    > > > There are four prerequisites for direct IO:
    > > > - the file needs to be opened with O_DIRECT
    > > > - the buffer needs to be page aligned (hint: use
    > > getpagesize() instead
    > > > of assuming that a page is 4k
    > > > - reads and writes need to happen *in* multiples
    > > of the soft block size
    > > > - reads and writes need to happen *at* multiples
    > > of the soft block size
    > >
    > > Actually, the buffer only needs to be hard block
    > > size aligned, same goes
    > > for the chunk size used for reads/writes.
    > >
    > > --
    > > Jens Axboe
    > >
    On 2.4 the open call succeeds with O_DIRECT
    but read returns -EINVAL for any block size (512,
    1024 ..16384)

    open("/tmp/midstress_idx10",
    O_RDWR|O_CREAT|O_DIRECT|O_LARGEFILE, 01001101270) =
    3
    read(3, 0xbfffdc40, 16384) = -1 EINVAL (Invalid
    argument)

    how to correct this problem ?





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