On Tue, Mar 08, 2005 at 08:07:57PM -0800, Joel Becker wrote: > On Tue, Mar 08, 2005 at 03:54:04PM -0800, Badari Pulavarty wrote: > > > 1. return EINVAL if the DIO goes past EOF. > > > > > > 2. truncate the request to file size (which is what your patch does) > > > and if it works, it works. > > > > > > 3. truncate the request to a size that actually works - like a multiple > > > of 512. > > > > > > 4. Do the full i/o since the user buffer is big enough, truncate the > > > result returned to file size (and clear out the user buffer where it > > > read past EOF). > > > > > > Number 4 would make it easy on the user-level code, but AIO DIO might be > > > a bit tricky and might be a security hole since the data would be dma'ed > > > there and then cleared. I need to look at the code some more. > > Solaris, which does forcedirectio as a mount option, actually > will do buffered I/O on the trailing part. Consider it like a bounce > buffer. That way they don't DMA the trailing data and succeed the I/O. > The I/O returns actual bytes till EOF, just like read(2) is supposed to. > Either this or a fully DMA'd number 4 is really what we should > do. If security can only be solved via a bounce buffer, who cares? If > the user created themselves a non-aligned file to open O_DIRECT, that's > their problem if the last part-sector is negligably slower.
If writes/truncates take care of zeroing out the rest of the sector on disk, might we still be OK without having to do the bounce buffer thing ? Regards Suparna > > -- > > Life's Little Instruction Book #3 > > "Watch a sunrise at least once a year." > > Joel Becker > Senior Member of Technical Staff > Oracle > E-mail: [EMAIL PROTECTED] > Phone: (650) 506-8127 > -- > To unsubscribe, send a message with 'unsubscribe linux-aio' in > the body to [EMAIL PROTECTED] For more info on Linux AIO, > see: http://www.kvack.org/aio/ > Don't email: <a href=mailto:"[EMAIL PROTECTED]">[EMAIL PROTECTED]</a> -- Suparna Bhattacharya ([EMAIL PROTECTED]) Linux Technology Center IBM Software Lab, India - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
