On Sun, 2015-04-05 at 23:59 +0900, Akinobu Mita wrote:
> The scatterlist for protection information which is passed to
> sbc_dif_verify_read() or sbc_dif_verify_write() requires that
> neighboring scatterlist entries are contiguous or chained so that they
> can be iterated by sg_next().
>
> However, the protection information for RD-MCP backends could be located
> in the multiple scatterlist arrays when the ramdisk space is too large.
> So if the read/write request straddles this boundary, sbc_dif_verify_read()
> or sbc_dif_verify_write() can't iterate all scatterlist entries.
>
> This fixes it by allocating temporary scatterlist if it is needed.
>
> Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
> Cc: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> Cc: Sagi Grimberg <sagig@xxxxxxxxxxxxxxxxxx>
> Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> Cc: target-devel@xxxxxxxxxxxxxxx
> Cc: linux-scsi@xxxxxxxxxxxxxxx
> ---
> * No change from v1
>
> drivers/target/target_core_rd.c | 39 +++++++++++++++++++++++++++++++++++----
> 1 file changed, 35 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/target/target_core_rd.c b/drivers/target/target_core_rd.c
> index ac5e8d2..6e25eaa 100644
> --- a/drivers/target/target_core_rd.c
> +++ b/drivers/target/target_core_rd.c
> @@ -390,11 +390,12 @@ static sense_reason_t rd_do_prot_rw(struct se_cmd *cmd, dif_verify dif_verify)
> struct se_device *se_dev = cmd->se_dev;
> struct rd_dev *dev = RD_DEV(se_dev);
> struct rd_dev_sg_table *prot_table;
> + bool need_to_release = false;
> struct scatterlist *prot_sg;
> u32 sectors = cmd->data_length / se_dev->dev_attrib.block_size;
> - u32 prot_offset, prot_page;
> + u32 prot_offset, prot_page, prot_npages;
> u64 tmp;
> - sense_reason_t rc;
> + sense_reason_t rc = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
>
> tmp = cmd->t_task_lba * se_dev->prot_length;
> prot_offset = do_div(tmp, PAGE_SIZE);
> @@ -404,10 +405,40 @@ static sense_reason_t rd_do_prot_rw(struct se_cmd *cmd, dif_verify dif_verify)
> if (!prot_table)
> return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
>
> - prot_sg = &prot_table->sg_table[prot_page -
> - prot_table->page_start_offset];
> + prot_npages = DIV_ROUND_UP(prot_offset + sectors * se_dev->prot_length,
> + PAGE_SIZE);
> +
> + /* prot pages straddles multiple scatterlist tables */
> + if (prot_table->page_end_offset < prot_page + prot_npages - 1) {
> + int i;
> +
> + prot_sg = kcalloc(prot_npages, sizeof(*prot_sg), GFP_KERNEL);
> + if (!prot_sg)
> + return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
> +
> + need_to_release = true;
> + sg_init_table(prot_sg, prot_npages);
> +
> + for (i = 0; i < prot_npages; i++) {
> + if (prot_page + i > prot_table->page_end_offset) {
> + prot_table = rd_get_prot_table(dev,
> + prot_page + i);
> + if (!prot_table)
> + goto out;
> + sg_unmark_end(&prot_sg[i - 1]);
> + }
> + prot_sg[i] = prot_table->sg_table[prot_page + i -
> + prot_table->page_start_offset];
> + }
> + } else {
> + prot_sg = &prot_table->sg_table[prot_page -
> + prot_table->page_start_offset];
> + }
>
Mmm, how about just explicitly doing sg_link() at prot_table scatterlist
creation time instead..?
That would save the extra allocation above, and AFAICT make for simpler
code.
--nab
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