On 1/15/25 1:29 PM, Shin'ichiro Kawasaki wrote:
> The current null_blk implementation checks if any bad blocks exist in
> the target blocks of each IO. If so, the IO fails and data is not
> transferred for all of the IO target blocks. However, when real storage
> devices have bad blocks, the devices may transfer data partially up to
> the first bad blocks (e.g., SAS drives). Especially, when the IO is a
> write operation, such partial IO leaves partially written data on the
> device.
>
> To simulate such partial IO using null_blk, introduce the new parameter
> 'badblocks_partial_io'. When this parameter is set,
> null_handle_badblocks() returns the number of the sectors for the
> partial IO as its third pointer argument. Pass the returned number of
> sectors to the following calls to null_handle_memory_backend() in
> null_process_cmd() and null_zone_write().
>
> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
A couple of nits below. Otherwise looks OK to me.
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
> +/*
> + * Check if the command should fail for the badblocks. If so, return
> + * BLK_STS_IOERR and return number of partial I/O sectors.
...and return the number of sectors that were read or written, which may be less
than the requested number of sectors.
> + *
> + * @cmd: The command to handle.
> + * @sector: The start sector for I/O.
> + * @nr_sectors: The caller specifies number of sectors to write or read.
> + * Returns number of sectors to be written or read for partial I/O.
@nr_sectors: Specifies number of sectors to read or write and returns the number
of sectors that were read or written.
> + */
> blk_status_t null_handle_badblocks(struct nullb_cmd *cmd, sector_t sector,
> - sector_t nr_sectors)
> + unsigned int *nr_sectors)
> {
> struct badblocks *bb = &cmd->nq->dev->badblocks;
> + struct nullb_device *dev = cmd->nq->dev;
> + unsigned int block_sectors = dev->blocksize >> SECTOR_SHIFT;
> sector_t first_bad;
> int bad_sectors;
> + unsigned int partial_io_sectors = 0;
>
> - if (!badblocks_check(bb, sector, nr_sectors, &first_bad, &bad_sectors))
> + if (!badblocks_check(bb, sector, *nr_sectors, &first_bad, &bad_sectors))
> return BLK_STS_OK;
>
> if (cmd->nq->dev->badblocks_once)
> badblocks_clear(bb, first_bad, bad_sectors);
>
> + if (cmd->nq->dev->badblocks_partial_io) {
> + if (!IS_ALIGNED(first_bad, block_sectors))
> + first_bad = ALIGN_DOWN(first_bad, block_sectors);
> + if (sector < first_bad)
> + partial_io_sectors = first_bad - sector;
> + }
> + *nr_sectors = partial_io_sectors;
> +
> return BLK_STS_IOERR;
> }
--
Damien Le Moal
Western Digital Research
