Lennert Buytenhek wrote:
> On Sun, Apr 01, 2001 at 11:47:15AM -0500, Russell Cattelan wrote:
>
> > Lennert Buytenhek wrote:
> >
> > > (Not on the list, please CC on replies)
> >
> > page aligned memory is necessary
>
> Doh. I know how O_DIRECT works, thank you. Please reread my original mail.
Arggh terribly sorry... guess I didn't have enough coffee yet this morning.
Guess we'll have to track down the return that isn't fliping the sign.
Thanks.
>
>
> > This isn't complete obviously but it is the basic code
> > to get a buffer that starts on a page boundary.
> >
> >
> > struct dioattr finfo;
> > ioctl(fd, XFS_IOC_DIOINFO, &finfo)
> > buf = (char *)malloc(<buffer size> +finfo.d_mem);
> > if( ((long)buf % finfo.d_mem != 0) ) {
> > buf += finfo.d_mem - ((long)buf % finfo.d_mem);
> > }
> >
> >
> >
> >
> > >
> > >
> > > Hi,
> > >
> > > Doing O_DIRECT I/O to a buffer which is not on an appropriate block
> > > boundary
> > > seem to fail with return code 22 instead of -22 (EINVAL). This is on 2.4.2
> > > with an XFS tree checkout from 20010329.
> > >
> > > tia,
> > > Lennert
> > >
> > > -- test.c
> > > #include <stdio.h>
> > > #include <stdlib.h>
> > > #include <fcntl.h>
> > > #include <sys/stat.h>
> > > #include <sys/types.h>
> > > #include <unistd.h>
> > >
> > > #define O_DIRECT 040000 /* direct disk access hint */
> > >
> > > int main()
> > > {
> > > char buf[16384];
> > > int fd;
> > > char *p;
> > >
> > > p = (char *)((((unsigned long)buf) + 8191) & ~8191L);
> > > fd = open("blah", O_CREAT | O_RDWR | O_DIRECT);
> > >
> > > printf("write returns %i\n", write(fd, buf, 8192));
> > > printf("write returns %i\n", write(fd, p, 1));
> > >
> > > return 0;
> > > }
> > > -- actual output
> > > [buytenh@mara test]$ ./test
> > > write returns 22
> > > write returns 22
> >
> > --
> > Russell Cattelan
> > cattelan@xxxxxxxxxxx
> >
> >
> >
--
Russell Cattelan
cattelan@xxxxxxxxxxx
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