Frank Mayhar <fmay...@google.com> writes:
> block: Force sector and nr_sects to device alignment and granularity.
>
> In blkdev_issue_discard(), rather than sending an improperly-
> aligned discard to the device (where it may get an error),
> adjust the start and length to the block device alignment and
> granularity. Don't fail if this leaves nothing to discard.
>
> Without this change, certain flash drivers can report invalid
> trim parameters (and will fail the command). Per tytso, "given
> that discards are advisory, any part of the storage stack is
> free to drop discard requests silently."
And how do you get here with misaligned discards?
-Jeff
>
> Signed-off-by: Frank Mayhar <fmay...@google.com>
> Reviewed-by: "Theodore Ts'o" <ty...@mit.edu>
>
> block/blk-lib.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/block/blk-lib.c b/block/blk-lib.c
> index 97a733c..a4472cd 100644
> --- a/block/blk-lib.c
> +++ b/block/blk-lib.c
> @@ -61,6 +61,21 @@ int blkdev_issue_discard(struct block_device *bdev,
> sector_t sector,
> alignment = (bdev_discard_alignment(bdev) >> 9) % granularity;
>
> /*
> + * Force sector and nr_sects to block device alignment and
> + * granularity.
> + */
> + if (alignment && (sector % alignment)) {
> + sector_t adj = alignment - (sector % alignment);
> +
> + sector += adj;
> + nr_sects -= adj;
> + }
> + if (nr_sects % granularity)
> + nr_sects -= nr_sects % granularity;
> + if (!nr_sects)
> + return ret;
> +
> + /*
> * Ensure that max_discard_sectors is of the proper
> * granularity, so that requests stay aligned after a split.
> */
>
>
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