On Wednesday 28 January 2015 18:00:25 Darrick J. Wong wrote:
> Create a new ioctl to expose the block layer's newfound ability to
> issue either a zeroing discard, a WRITE SAME with a zero page, or a
> regular write with the zero page. This BLKZEROOUT2 ioctl takes
> {start, length, flags} as parameters. So far, the only flag available
> is to enable the zeroing discard part -- without it, the call invokes
> the old BLKZEROOUT behavior. start and length have the same meaning
> as in BLKZEROOUT.
>
> Furthermore, because BLKZEROOUT2 issues commands directly to the
> storage device, we must invalidate the page cache (as a regular
> O_DIRECT write would do) to avoid returning stale cache contents at a
> later time.
>
> This patch depends on "block: Add discard flag to
> blkdev_issue_zeroout() function" in Jens' for-3.20/core branch.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
Would this work ok for devices that fill discarded areas with all-ones
instead of all-zeroes? I believe SD cards can do either.
Arnd
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