From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
transport_calc_sg_num() is used by dev_obj_do_se_mem_map() to determine
the number of scatterlists for an individual struct se_task, and then proceeds
to allocate a contigious array of struct scatterlist in struct se_task->task_sg[].
This struct se_task->task_sg[] is then used by subsystem plugins like IBLOCK, FILEIO
and PSCSI to setup I/O descriptors down to the Linux storage subsystem.
This patch updates transport_calc_sg_num() to fix an issue that was originally
reported when an underlying struct Scsi_Host was reporting 255 max_sectors to
IBLOCK, which manifested itself by generating an number of scatterlists for
the map task_offset carried between struct se_task allocations inside of
transport_generic_get_cdb_count().
This patch also makes an small improvement by removing the improper usage of
list_for_each_entry_continue() when picking off the next struct se_mem, and
instead adds a !list_is_last() check around list_entry().
So far this patch has been tested with TCM_Loop using max_sectors=1024 on top of
TCM/IBLOCK connected to a scsi_debug device using max_sectors 255-251 to force the
task_offset to span struct task allocations.
Signed-off-by: Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx>
---
drivers/target/target_core_transport.c | 45 +++++++++++++++++---------------
1 files changed, 24 insertions(+), 21 deletions(-)
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index dbedb7a..43eeb14 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -6554,54 +6554,57 @@ extern u32 transport_calc_sg_num(
struct se_mem *in_se_mem,
u32 task_offset)
{
+ struct se_cmd *se_cmd = task->task_se_cmd;
struct se_mem *se_mem = in_se_mem;
- u32 sg_length, sg_offset, task_size = task->task_size;
- u32 saved_task_offset = 0;
+ u32 sg_length, task_size = task->task_size;
- while (task_size) {
+ while (task_size != 0) {
DEBUG_SC("se_mem->se_page(%p) se_mem->se_len(%u)"
" se_mem->se_off(%u) task_offset(%u)\n",
se_mem->se_page, se_mem->se_len,
se_mem->se_off, task_offset);
if (task_offset == 0) {
- if (task_size > se_mem->se_len)
+ if (task_size >= se_mem->se_len) {
sg_length = se_mem->se_len;
- else
+
+ if (!(list_is_last(&se_mem->se_list,
+ T_TASK(se_cmd)->t_mem_list)))
+ se_mem = list_entry(se_mem->se_list.next,
+ struct se_mem, se_list);
+ } else {
sg_length = task_size;
+ task_size -= sg_length;
+ goto next;
+ }
DEBUG_SC("sg_length(%u) task_size(%u)\n",
sg_length, task_size);
-
- if (saved_task_offset)
- task_offset = saved_task_offset;
} else {
- sg_offset = task_offset;
-
- if ((se_mem->se_len - task_offset) > task_size)
+ if ((se_mem->se_len - task_offset) > task_size) {
sg_length = task_size;
- else
+ task_size -= sg_length;
+ goto next;
+ } else {
sg_length = (se_mem->se_len - task_offset);
+ if (!(list_is_last(&se_mem->se_list,
+ T_TASK(se_cmd)->t_mem_list)))
+ se_mem = list_entry(se_mem->se_list.next,
+ struct se_mem, se_list);
+ }
+
DEBUG_SC("sg_length(%u) task_size(%u)\n",
sg_length, task_size);
- saved_task_offset = task_offset;
task_offset = 0;
}
task_size -= sg_length;
-
+next:
DEBUG_SC("task[%u] - Reducing task_size to(%u)\n",
task->task_no, task_size);
task->task_sg_num++;
-
- list_for_each_entry_continue(se_mem,
- task->task_se_cmd->t_task->t_mem_list, se_list)
- break;
-
- if (!se_mem)
- break;
}
task->task_sg = kzalloc(task->task_sg_num *
--
1.5.6.5
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