So, uh, it's been a couple of weeks...
Jens: Any comments? Nobody's objected to either the function or the interface;
can this go in -next?
--D
On Wed, Jan 28, 2015 at 06:00:25PM -0800, 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>
> ---
> block/ioctl.c | 45 ++++++++++++++++++++++++++++++++++++++-------
> include/uapi/linux/fs.h | 7 +++++++
> 2 files changed, 45 insertions(+), 7 deletions(-)
>
> diff --git a/block/ioctl.c b/block/ioctl.c
> index 7d8befd..ff623d5 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -186,19 +186,39 @@ static int blk_ioctl_discard(struct block_device *bdev, uint64_t start,
> }
>
> static int blk_ioctl_zeroout(struct block_device *bdev, uint64_t start,
> - uint64_t len)
> + uint64_t len, uint32_t flags)
> {
> + int ret;
> + struct address_space *mapping;
> + uint64_t end = start + len - 1;
> +
> + if (flags & ~BLKZEROOUT2_DISCARD_OK)
> + return -EINVAL;
> if (start & 511)
> return -EINVAL;
> if (len & 511)
> return -EINVAL;
> - start >>= 9;
> - len >>= 9;
> -
> - if (start + len > (i_size_read(bdev->bd_inode) >> 9))
> + if (end >= i_size_read(bdev->bd_inode))
> return -EINVAL;
>
> - return blkdev_issue_zeroout(bdev, start, len, GFP_KERNEL, false);
> + /* Invalidate the page cache, including dirty pages */
> + mapping = bdev->bd_inode->i_mapping;
> + truncate_inode_pages_range(mapping, start, end);
> +
> + ret = blkdev_issue_zeroout(bdev, start >> 9, len >> 9, GFP_KERNEL,
> + flags & BLKZEROOUT2_DISCARD_OK);
> + if (ret)
> + goto out;
> +
> + /*
> + * Invalidate again; if someone wandered in and dirtied a page,
> + * the caller will be given -EBUSY.
> + */
> + ret = invalidate_inode_pages2_range(mapping,
> + start >> PAGE_CACHE_SHIFT,
> + end >> PAGE_CACHE_SHIFT);
> +out:
> + return ret;
> }
>
> static int put_ushort(unsigned long arg, unsigned short val)
> @@ -326,7 +346,18 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
> if (copy_from_user(range, (void __user *)arg, sizeof(range)))
> return -EFAULT;
>
> - return blk_ioctl_zeroout(bdev, range[0], range[1]);
> + return blk_ioctl_zeroout(bdev, range[0], range[1], 0);
> + }
> + case BLKZEROOUT2: {
> + struct blkzeroout2 p;
> +
> + if (!(mode & FMODE_WRITE))
> + return -EBADF;
> +
> + if (copy_from_user(&p, (void __user *)arg, sizeof(p)))
> + return -EFAULT;
> +
> + return blk_ioctl_zeroout(bdev, p.start, p.length, p.flags);
> }
>
> case HDIO_GETGEO: {
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 3735fa0..54d24ea 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -150,6 +150,13 @@ struct inodes_stat_t {
> #define BLKSECDISCARD _IO(0x12,125)
> #define BLKROTATIONAL _IO(0x12,126)
> #define BLKZEROOUT _IO(0x12,127)
> +struct blkzeroout2 {
> + __u64 start;
> + __u64 length;
> + __u32 flags;
> +};
> +#define BLKZEROOUT2_DISCARD_OK 1
> +#define BLKZEROOUT2 _IOR(0x12, 127, struct blkzeroout2)
>
> #define BMAP_IOCTL 1 /* obsolete - kept for compatibility */
> #define FIBMAP _IO(0x00,1) /* bmap access */
> --
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