Messages in this thread | | | Subject | Re: O_DIRECT alignment requirements ? | Date | Wed, 09 Apr 2003 18:53:17 +0200 | From | Rob van Nieuwkerk <> |
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Joel Becker wrote: > On Wed, Apr 09, 2003 at 02:16:08PM +0200, Rob van Nieuwkerk wrote: > > I plan to use O_DIRECT in my application (on a partition, no fs). > > It is hard to find info on the exact requirements on the mandatory > > alignments of buffer, offset, transfer size: it's easy to find many > > contradicting documents. And checking the kernel source itself isn't > > trivial. > > In 2.4, your buffer, offset, and transfer size must be soft > blocksize aligned. That's the output of BLKBSZGET against the block > device. For unmounted partitions that is 512b, for most people's ext3 > filesystems that is 4K. It is, FYI, the number set by set_blocksize().
Hi Joel,
Thank you for your reaction.
I get 4096 with BLKBSZGET on several unmounted partitions on my system (RH 2.4.18-27.7.x kernel). Some give 1024 .. Maybe it is because I had them mounted first and unmounted them for the test ?
greetings, Rob van Nieuwkerk - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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