Re: O_DIRECT

[Shesha Sreenivasamurthy <shesha@xxxxxxxxxxx>]

Usually what you do is, partition the disk, create filesystem and read or write files.
  Reading and writing is without a filesystem.
   Assume you have maintained some superblock information of your own driver say last 512 bytes you have designated as superblock. You can seek to that position and read the last 512 bytes which is meaningful only to you. Note that I am read/writing raw bytes not any file. Therefore you can read/write without a filesystem and even without any partition,

-Shesha


Devel wrote:

Hi all,
how i can write data on a partition without a filesystem??

Saluti Carlo!

Il Tue, 20 Jul 2004 20:48:24 +0200
bert hubert <ahu@xxxxxxx> scrisse:

  

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!

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