2015-04-05 19:10 GMT+09:00 Sagi Grimberg <sagig@xxxxxxxxxxxxxxxxxx>:
> On 4/4/2015 3:24 PM, 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: Asias He <asias@xxxxxxxxxx>
>> 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
>> ---
>> 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 4d614c9..19c893d 100644
>> --- a/drivers/target/target_core_rd.c
>> +++ b/drivers/target/target_core_rd.c
>> @@ -387,11 +387,12 @@ static sense_reason_t rd_do_prot_rw(struct se_cmd
>> *cmd, bool is_write)
>> 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;
>> sense_reason_t (*dif_verify)(struct se_cmd *, sector_t, unsigned
>> int,
>> unsigned int, struct scatterlist *, int) =
>> is_write ? sbc_dif_verify_write : sbc_dif_verify_read;
>> @@ -404,10 +405,40 @@ static sense_reason_t rd_do_prot_rw(struct se_cmd
>> *cmd, bool is_write)
>> 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];
>> + }
>>
>> rc = dif_verify(cmd, cmd->t_task_lba, sectors, 0, prot_sg,
>> prot_offset);
>> +out:
>> + if (need_to_release)
>> + kfree(prot_sg);
>
>
> I think it is safe to free prot_sg if you just make sure to initialize
> it to NULL at declaration time, no need for 'need_to_release'.
'need_to_release' is required to avoid kfree when 'prot_sg' is
initialized to a pointer in the real prot space (i.e. "else" case above).
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