Re: A problem about DIRECT IO on ext3

[li nux <lnxluv@yahoo.com>]

--- 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) = 4
read(3, 0xbfffdc40, 16384) = -1 EINVAL (Invalid
argument)

how to correct this problem ?



		
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