2015-04-08 14:13 GMT+09:00 Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx>:
> 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..?
Yeap, that would be an optimal solution. But some architectures don't
support sg chaining (i.e. !CONFIG_ARCH_HAS_SG_CHAIN).
> That would save the extra allocation above, and AFAICT make for simpler
> code.
Do you prefer fixing it conditionally with using #ifdef ? (i.e.
sg chaining at creating time if CONFIG_ARCH_HAS_SG_CHAIN is defined,
otherwise do the extra allocation above) If so, I'll resubmit the
patch with such changes.
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