Re: O_DIRECT

[Shesha Sreenivasamurthy <shesha@xxxxxxxxxxx>]

Thank you very much Hubert.

Regarding my second question, what I mean is, to calculate the soft block size of a partition on which there is no filesystem created, I am using the IOCTL "BLKBSZGET".

int soft_blk_size;
int dev=open("/dev/sda11", O_RDWR | O_DIRECT);
ioctl(dev, BLKBSZGET, &soft_blk_size);
printf ("SOFT BLOCK SIZE=%d\n", soft_blk_size);

Thanking You
Shesha

bert hubert wrote:

On Tue, Jul 20, 2004 at 10:27:57AM -0700, Shesha Sreenivasamurthy wrote:
  

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.
    

As fas as I know, yes, but be aware that O_DIRECT requires page aligned
addresses! (an integral of 4096 on most systems).

  

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

No idea what you mean - but see above about the aligned addresses.

  

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

I see no reason why not. Good luck!