Message-ID: <020001c3b32c$70607b50$c100a8c0@wakatipu>
From: "Michael Kerrisk" <mtk-lists@jambit.com>
To: <dhruv.anand@wipro.com>
Cc: <linux-kernel@vger.kernel.org>
References: <1E27FF611EBEFB4580387FCB5BEF00F3013DEF08@blr-ec-msg04.wipro.com>
Subject: Re: DIRECT IO for ext3/ext2.
Date: Tue, 25 Nov 2003 09:16:34 +0100
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> Thanks for your reply. I looked into the boundary alignment issue.
> Observed something strange happening;
>
> I wrote my own kernel module and then;
> 1. retrieved the block size = 4096 using block_size(struct block_device
> *bdev)
> 2. in the user application i did a lseek by 4906 (block size seek)
> 3. then found the address of the variable i wanted to read into, to be
> block
>    size aligned.
>
> However, the read still seems to fail with the O_DIRECT flag specified.
> The same check _passes if i do not specify the flag in open of the
> device.
>
> Boundary issues seem to be not the cause of failure here.
> Would have any more kind suggestions on something that i should do or
> could be missing on?

Is the size of the data you are reading also a multiple the block size?  (It
should be.)

Cheers,

Michael

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