DIRECT IO for ext3/ext2.

[dhruv.anand]

Hi,
I am working on an application on linux-2.6 that needs to
bypass the buffer cache. In order to do so i use the direct
IO functionality. Although open to the device succeeds with
the DIRECT_IO flag, read from the device fails.

Following is the exceprt fromt he code to open and read;
--------------------------------------------------------

if ((devf = open(dumpdev, O_RDONLY | O_DIRECT, 0)) < 0) {
     fprintf(KL_ERRORFP, "Error: open failed!\n");
     ...
}

if(err = read(devf, &magic_nr, sizeof(magic_nr)) != sizeof(magic_nr)) {
     fprintf(KL_ERRORFP, "Error: read() failed!\n");
      ...
}

---------------------------------------------------------
I am returned an errno=22, indicating 'Invalid argument'

I would appreciate it, if you could knowledge me importantly about
the completeness of the 'direct IO' functionality in ext3 file-system.
Or if i am doing something wrong in usage?


Regards
Dhruv.
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