On 8/14/2015 4:15 PM, Jeff Moyer wrote:
> commit bbab37ddc20b (block: Add support for DAX reads/writes to
> block devices) caused a regression in mkfs.xfs. That utility
> sets the block size of the device to the logical block size
> using the BLKBSZSET ioctl, and then issues a single sector read
> from the last sector of the device. This results in the dax_io
> code trying to do a page-sized read from 512 bytes from the end
> of the device. The result is -ERANGE being returned to userspace.
>
> The fix is to align the block to the page size before calling
> get_block.
>
> Thanks to willy for simplifying my original patch.
>
> Signed-off-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Tested-by: Linda Knippers <linda.knippers@xxxxxx>
> ---
> fs/dax.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index a7f77e1..ef35a20 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -116,7 +116,8 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
> unsigned len;
> if (pos == max) {
> unsigned blkbits = inode->i_blkbits;
> - sector_t block = pos >> blkbits;
> + long page = pos >> PAGE_SHIFT;
> + sector_t block = page << (PAGE_SHIFT - blkbits);
> unsigned first = pos - (block << blkbits);
> long size;
>
>
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