Re: [PATCH 1/2] tcm: Add support for BIDI operation andXDWRITE_READ_10 emulation
From: Nicholas A. Bellinger
Date: Wed Sep 15 2010 - 16:33:37 EST
On Wed, 2010-09-15 at 17:14 +0200, Boaz Harrosh wrote:
> On 09/15/2010 02:06 PM, Nicholas A. Bellinger wrote:
> > From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> >
> > This patch series adds DMA_BIDIRECTIONAL support to TCM Core. This
> > includes the following for struct se_cmd to handle BIDI READ payloads using a new
> > struct se_transport_task->t_mem_bidi_list and struct se_transport_task->t_tasks_se_bidi_num.
> > The model used to keep the WRITE payload at struct se_transport_task->t_mem_list,
> > and add a new READ payload memory list at struct se_transport_task->t_mem_bidi_list.
> >
> > *) desciptor setup:
> >
> > This patch adds support for XDWRITEREAD_10 within transport_generic_cmd_sequencer(),
> > and sets up the new struct se_cmd->transport_xor_callback() completion function
> > at transport_xor_callback(). It then updates transport_new_cmd_obj() to handle the
> > BIDI READ case.
> >
> > It also adds support for DMA_BIDIRECTIONAL to transport_generic_map_mem_to_cmd()
> > to setup struct se_transport_task->t_mem_bidi_list for BIDI READ payloads
> >
> > *) memory mapping:
> >
> > This patch updates transport_generic_get_cdb_count() to accept a enum dma_data_direction
> > parameter to handle the BIDI and the existing WRITE/READ cases for SCF_SCSI_DATA_SG_IO_CDB.
> > This patch also updates transport_generic_map_mem_to_cmd() to accept a 'void *mem_bidi_in'
> > and 'u32 se_mem_bidi_num' from BIDI capable TCM fabric modules.
> >
> > It then updates transport_generic_get_task() and struct se_cmd->transport_get_task()
> > to accept a enum dma_data_direction function parameter.
> >
> > *) descriptor callback:
> >
> > For the struct se_cmd callback, it updates transport_generic_complete_ok() to support
> > DMA_BIDIRECTIONAL and looks for the new struct se_cmd->transport_xor_callback() in
> > transport_generic_cmd_sequencer() to perform the post READ/WRITE XOR emulation.
> > This also includes the additon of transport_memcpy_se_mem_read_contig() used to copy the
> > WRITE scatterlists into a local contigious buffer for the XOR instructions within
> > transport_xor_callback();
> >
> > *) descriptor release:
> >
> > Update transport_free_pages() to walk the new T_TASK(cmd)->t_mem_bidi_list (when available)
> > and release struct se_mem and pages.
> >
> > So far this has been tested with TCM_Loop using BSG w/ userspace code generating
> > BIDI XDWRITE_READ_10 CDBs.
> >
>
> Hi.
>
> OK so lets see if we can manage with the scsi-ml model of:
>
> BIDI-COMMANDS ==> data_direction == DMA_TO_DEVICE && se_transport_task->t_mem_bidi is present
This makes perfect sense.. I will removing the use of DMA_BIDIRECTIONAL
from TCM Core, and follow the above logic to signal BIDI-COMMAND usage.
>
> > Signed-off-by: Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx>
> > ---
> > drivers/target/target_core_transport.c | 282 ++++++++++++++++++++++++++++----
> > include/target/target_core_base.h | 9 +-
> > include/target/target_core_transport.h | 10 +-
> > 3 files changed, 261 insertions(+), 40 deletions(-)
> >
> > diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
> > index 517a59c..37afc39 100644
> > --- a/drivers/target/target_core_transport.c
> > +++ b/drivers/target/target_core_transport.c
> > @@ -2529,7 +2529,8 @@ static inline int transport_check_device_cdb_sector_count(
> > static struct se_task *transport_generic_get_task(
> > struct se_transform_info *ti,
> > struct se_cmd *cmd,
> > - void *se_obj_ptr)
> > + void *se_obj_ptr,
> > + enum dma_data_direction data_direction)
>
> We don't need this direction I think
This is required because we expect to have the T_TASK(cmd)->t_mem_list
for BIDI WRITE and T_TASK(cmd)->t_mem_bidi_list for BIDI READ, eg: this
will be called multiple times individually to satisfy the BIDI WRITE and
READ portions of the struct se_cmd.
>
> > {
> > struct se_task *task;
> > struct se_device *dev = SE_DEV(cmd);
> > @@ -2625,7 +2626,8 @@ static int transport_process_control_sg_transform(
> > return -1;
> > }
> >
> > - task = cmd->transport_get_task(ti, cmd, ti->se_obj_ptr);
> > + task = cmd->transport_get_task(ti, cmd, ti->se_obj_ptr,
> > + cmd->data_direction);
>
> I can't seem to find the changed implementation of cmd->transport_get_task
> in this patch or the next one. But it seems this here is just a pass throw
> to cmd->transport_get_task so the argument should go there.
Yes, cmd->transport_get_task() translates to the above
transport_generic_get_task(). It is slightly confusing, and I may end
up dropping this now and just use transport_generic_get_task() directly
in a seperate patch, so please ignore this for the moment.. :-)
>
> > if (!(task))
> > return -1;
> >
> > @@ -2665,7 +2667,8 @@ static int transport_process_control_nonsg_transform(
> > unsigned char *cdb;
> > struct se_task *task;
> >
> > - task = cmd->transport_get_task(ti, cmd, ti->se_obj_ptr);
> > + task = cmd->transport_get_task(ti, cmd, ti->se_obj_ptr,
> > + cmd->data_direction);
>
> Same
>
> > if (!(task))
> > return -1;
> >
> > @@ -2699,7 +2702,8 @@ static int transport_process_non_data_transform(
> > unsigned char *cdb;
> > struct se_task *task;
> >
> > - task = cmd->transport_get_task(ti, cmd, ti->se_obj_ptr);
> > + task = cmd->transport_get_task(ti, cmd, ti->se_obj_ptr,
> > + cmd->data_direction);
>
> Same
>
> > if (!(task))
> > return -1;
> >
> > @@ -5183,6 +5187,54 @@ int transport_generic_emulate_request_sense(
> > }
> > EXPORT_SYMBOL(transport_generic_emulate_request_sense);
> >
> > +static void transport_xor_callback(struct se_cmd *cmd)
> > +{
> > + unsigned char *buf, *addr;
> > + struct se_mem *se_mem;
> > + unsigned int offset;
> > + int i;
> > + /*
> > + * From sbc3r22.pdf section 5.48 XDWRITEREAD (10) command
> > + *
> > + * 1) read the specified logical block(s);
> > + * 2) transfer logical blocks from the data-out buffer;
> > + * 3) XOR the logical blocks transferred from the data-out buffer with
> > + * the logical blocks read, storing the resulting XOR data in a buffer;
> > + * 4) if the DISABLE WRITE bit is set to zero, then write the logical
> > + * blocks transferred from the data-out buffer; and
> > + * 5) transfer the resulting XOR data to the data-in buffer.
> > + */
> > + buf = kmalloc(cmd->data_length, GFP_KERNEL);
> > + if (!(buf)) {
> > + printk(KERN_ERR "Unable to allocate xor_callback buf\n");
> > + return;
> > + }
> > + /*
> > + * Copy the scatterlist WRITE buffer located at T_TASK(cmd)->t_mem_list
> > + * into the locally allocated *buf
> > + */
> > + transport_memcpy_se_mem_read_contig(cmd, buf, T_TASK(cmd)->t_mem_list);
>
> This is not relevant to our discussion but did you copy the out-buffer to a
> contiguous buffer so not to juggle a double-list traversal? Or am I missing
> something more cardinal.
>
Yeah, I was simply following what scsi_debug.c currently does in this
regard.
> If so the a TODO: comment might be in place. Surely it's possible to walk
> two sg-list lists and xor them.
The thing is that we are dealing with the linked list struct se_mem
style memory here, and not a struct scatterlist array and/or chained
links. This is because the scatterlists live in struct
se_task->task_sg[] which are arrays that be mapped out into the TCM
struct se_subsystem_api to IBLOCK, FILEIO, pSCSI, etc.
There is actually a case for HW target mode in
transport_do_task_sg_chain() where we chain together each of the struct
se_task->task_sg[] in order to use pci_map_sg() here.. I was thinking
about doing something similar for BIDI (and I still need to look at BIDI
for HW target mode), but really it's more trouble than it's worth using
it here.
>
> > + /*
> > + * Now perform the XOR against the BIDI read memory located at
> > + * T_TASK(cmd)->t_mem_bidi_list
> > + */
> > +
> > + offset = 0;
> > + list_for_each_entry(se_mem, T_TASK(cmd)->t_mem_bidi_list, se_list) {
> > + addr = (unsigned char *)kmap_atomic(se_mem->se_page, KM_USER0);
> > + if (!(addr))
> > + goto out;
> > +
> > + for (i = 0; i < se_mem->se_len; i++)
> > + *(addr + se_mem->se_off + i) ^= *(buf + offset + i);
> > +
> > + offset += se_mem->se_len;
> > + kunmap_atomic(addr, KM_USER0);
> > + }
> > +out:
> > + kfree(buf);
> > +}
> > +
> > /*
> > * Used to obtain Sense Data from underlying Linux/SCSI struct scsi_cmnd
> > */
> > @@ -5472,6 +5524,25 @@ static int transport_generic_cmd_sequencer(
> > T_TASK(cmd)->t_tasks_fua = (cdb[1] & 0x8);
> > ret = TGCS_DATA_SG_IO_CDB;
> > break;
> > + case XDWRITEREAD_10:
> > + SET_GENERIC_TRANSPORT_FUNCTIONS(cmd);
> > + if (cmd->data_direction != DMA_BIDIRECTIONAL)
> > + return TGCS_INVALID_CDB_FIELD;
>
> Just check for the presences of the bidi_list. Where is it?
Ok, this will become a:
if (cmd->data_direction != DMA_TO_DEVICE)
check, because the t_mem_bidi_list has not been setup at this point..
>
> > + sectors = transport_get_sectors_10(cdb, cmd, §or_ret);
> > + if (sector_ret)
> > + return TGCS_UNSUPPORTED_CDB;
> > + size = transport_get_size(sectors, cdb, cmd);
> > + transport_dev_get_mem_SG(cmd->se_orig_obj_ptr, cmd);
> > + transport_get_maps(cmd);
> > + cmd->transport_split_cdb = &split_cdb_XX_10;
> > + cmd->transport_get_lba = &transport_lba_32;
> > + /*
> > + * Setup BIDI XOR callback to be run during transport_generic_complete_ok()
> > + */
> > + cmd->transport_xor_callback = &transport_xor_callback;
> > + T_TASK(cmd)->t_tasks_fua = (cdb[1] & 0x8);
> > + ret = TGCS_DATA_SG_IO_CDB;
> > + break;
> > case 0xa3:
> > SET_GENERIC_TRANSPORT_FUNCTIONS(cmd);
> > if (TRANSPORT(dev)->get_device_type(dev) != TYPE_ROM) {
> > @@ -5842,9 +5913,10 @@ static int transport_generic_cmd_sequencer(
> >
> > cmd->cmd_spdtl = size;
> >
> > - if (cmd->data_direction == DMA_TO_DEVICE) {
> > + if ((cmd->data_direction == DMA_TO_DEVICE) ||
> > + (cmd->data_direction == DMA_BIDIRECTIONAL)) {
> > printk(KERN_ERR "Rejecting underflow/overflow"
> > - " WRITE data\n");
> > + " WRITE or BIDI data\n");
>
> The data_direction == DMA_TO_DEVICE will stay with our alternate model
> so this does not change
<nod>
>
> > return TGCS_INVALID_CDB_FIELD;
> > }
> > /*
> > @@ -6096,6 +6168,33 @@ void transport_memcpy_read_contig(
> > }
> > EXPORT_SYMBOL(transport_memcpy_read_contig);
> >
> > +void transport_memcpy_se_mem_read_contig(
> > + struct se_cmd *cmd,
> > + unsigned char *dst,
> > + struct list_head *se_mem_list)
> > +{
> > + struct se_mem *se_mem;
> > + void *src;
> > + u32 length = 0, total_length = cmd->data_length;
> > +
> > + list_for_each_entry(se_mem, se_mem_list, se_list) {
> > + length = se_mem->se_len;
> > +
> > + if (length > total_length)
> > + length = total_length;
> > +
> > + src = page_address(se_mem->se_page) + se_mem->se_off;
> > +
> > + memcpy(dst, src, length);
> > +
> > + if (!(total_length -= length))
> > + return;
> > +
> > + dst += length;
> > + }
> > +}
> > +
> > +
> > /* transport_generic_passthrough():
> > *
> > *
> > @@ -6252,6 +6351,18 @@ void transport_generic_complete_ok(struct se_cmd *cmd)
> >
> > switch (cmd->data_direction) {
> > case DMA_FROM_DEVICE:
> > + case DMA_BIDIRECTIONAL:
> > + /*
> > + * Check for the XOR BIDI callback emulation for XD_WRITEREAD_*
> > + */
> > + if (cmd->transport_xor_callback) {
>
> What? this one place is a bad hack. There are 200 and some BIDI commands in the
> scsi-protocol. XOR is just a small group of them. Do you intend to add such an if
> for every command type? I don't think so. The target in question should just be
> able to proprly hook into the transport_complete mechanics and clean after itself
> some how. What does the cmd->transport_xor_callback do? Why no just do a:
>
> if (cmd->transport_complete__callback)
> cmd->transport_complete_callback(cmd);
>
> for any kind of direction, as a target set policy. (When there are chained
> processing to do)
Hmmmmm, the thing is that this particular xor callback is not required
for non XOR BIDI operation, but point taken on naming it something
generic. I do agree that a cmd->transport_complete_callback() may be
more useful for this.
>
> > + /*
> > + * For fully emulated HBAs, this will translate to
> > + * transport_xor_callback()
> > + */
> > + cmd->transport_xor_callback(cmd);
> > + }
> > +
>
> > spin_lock(&cmd->se_lun->lun_sep_lock);
> > if (SE_LUN(cmd)->lun_sep) {
> > SE_LUN(cmd)->lun_sep->sep_stats.tx_data_octets +=
> > @@ -6347,6 +6458,23 @@ static inline void transport_free_pages(struct se_cmd *cmd)
> > kmem_cache_free(se_mem_cache, se_mem);
> > }
> >
> > + if (T_TASK(cmd)->t_mem_bidi_list && T_TASK(cmd)->t_tasks_se_bidi_num) {
>
> See here: we have a buffer we take care of it. Simple
<nod>
>
> > + list_for_each_entry_safe(se_mem, se_mem_tmp,
> > + T_TASK(cmd)->t_mem_bidi_list, se_list) {
> > + /*
> > + * We only release call __free_page(struct se_mem->se_page) when
> > + * SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC is NOT in use,
> > + */
> > + if (free_page)
> > + __free_page(se_mem->se_page);
> > +
> > + list_del(&se_mem->se_list);
> > + kmem_cache_free(se_mem_cache, se_mem);
> > + }
> > + }
> > +
> > + kfree(T_TASK(cmd)->t_mem_bidi_list);
> > + T_TASK(cmd)->t_mem_bidi_list = NULL;
> > kfree(T_TASK(cmd)->t_mem_list);
> > T_TASK(cmd)->t_mem_list = NULL;
> > T_TASK(cmd)->t_tasks_se_num = 0;
> > @@ -6477,18 +6605,34 @@ release_cmd:
> > int transport_generic_map_mem_to_cmd(
> > struct se_cmd *cmd,
> > void *mem,
> > - u32 se_mem_num)
> > + u32 se_mem_num,
> > + void *mem_bidi_in,
> > + u32 se_mem_bidi_num)
> > {
> > u32 se_mem_cnt_out = 0;
> > int ret;
> >
> > if (!(mem) || !(se_mem_num))
> > return 0;
> > +
> > + if ((cmd->data_direction == DMA_BIDIRECTIONAL) &&
> > + (!(mem_bidi_in) || !(se_mem_bidi_num))) {
> > + printk(KERN_ERR "Unable to process DMA_BIDIRECTIONAL with mem_bidi_in:"
> > + " %p and se_mem_bidi_num: %u\n", mem_bidi_in, se_mem_bidi_num);
> > + return -EINVAL;
> > + }
> > +
>
> In our new model this just drops. Because only one member caries information. mem_bidi_in
> is the flag for bidi presence.
<nod>
>
> > /*
> > * Passed *mem will contain a list_head containing preformatted
> > * struct se_mem elements...
> > */
> > if (!(cmd->se_cmd_flags & SCF_PASSTHROUGH_SG_TO_MEM)) {
> > + if (cmd->data_direction == DMA_BIDIRECTIONAL) {
> > + printk(KERN_ERR "SCF_CMD_PASSTHROUGH_NOALLOC not supported"
> > + " with DMA_BIDIRECTIONAL\n");
> > + return -ENOSYS;
>
> What is the issue here. Why can't we bidi in this case?
This assumes incoming struct se_mem memory for *mem, and not struct
scatterlist. This flag is only used for some special internal
passthrough cases for getting INQUIRY, et al, so this is just a safety
check..
>
> > + }
> > +
> > T_TASK(cmd)->t_mem_list = (struct list_head *)mem;
> > T_TASK(cmd)->t_tasks_se_num = se_mem_num;
> > cmd->se_cmd_flags |= SCF_CMD_PASSTHROUGH_NOALLOC;
> > @@ -6507,14 +6651,35 @@ int transport_generic_map_mem_to_cmd(
> > */
> > T_TASK(cmd)->t_mem_list = transport_init_se_mem_list();
> > if (!(T_TASK(cmd)->t_mem_list))
> > - return -1;
> > + return -ENOMEM;
> >
> > ret = transport_map_sg_to_mem(cmd,
> > T_TASK(cmd)->t_mem_list, mem, &se_mem_cnt_out);
> > if (ret < 0)
> > - return -1;
> > + return -ENOMEM;
>
> These two belong to another patch right?
Sorry, Konrad has got me doing this conversion automatically now..
>
> >
> > T_TASK(cmd)->t_tasks_se_num = se_mem_cnt_out;
> > + /*
> > + * Setup BIDI READ list of struct se_mem elements
> > + */
> > + if (cmd->data_direction == DMA_BIDIRECTIONAL) {
>
> Just if (mem_bidi_in) no?
<nod>
>
> > + T_TASK(cmd)->t_mem_bidi_list = transport_init_se_mem_list();
> > + if (!(T_TASK(cmd)->t_mem_bidi_list)) {
> > + kfree(T_TASK(cmd)->t_mem_list);
> > + return -ENOMEM;
> > + }
> > + se_mem_cnt_out = 0;
> > +
> > + ret = transport_map_sg_to_mem(cmd,
> > + T_TASK(cmd)->t_mem_bidi_list, mem_bidi_in,
> > + &se_mem_cnt_out);
> > + if (ret < 0) {
> > + kfree(T_TASK(cmd)->t_mem_list);
> > + return -ENOMEM;
> > + }
> > +
> > + T_TASK(cmd)->t_tasks_se_bidi_num = se_mem_cnt_out;
> > + }
> > cmd->se_cmd_flags |= SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC;
> >
> > } else if (cmd->se_cmd_flags & SCF_SCSI_CONTROL_NONSG_IO_CDB) {
> > @@ -6610,6 +6775,11 @@ non_scsi_data:
> > */
> > int transport_generic_do_transform(struct se_cmd *cmd, struct se_transform_info *ti)
> > {
> > + if (!(cmd->transport_cdb_transform)) {
> > + dump_stack();
> > + return -1;
> > + }
> > +
> > if (cmd->transport_cdb_transform(cmd, ti) < 0)
> > return -1;
> >
> > @@ -6656,9 +6826,9 @@ int transport_new_cmd_obj(
> > struct se_transform_info *ti,
> > int post_execute)
> > {
> > - u32 task_cdbs = 0;
> > - struct se_mem *se_mem_out = NULL;
> > struct se_device *dev = SE_DEV(cmd);
> > + enum dma_data_direction data_direction;
> > + u32 task_cdbs = 0, rc;
> >
> > if (!(cmd->se_cmd_flags & SCF_SCSI_DATA_SG_IO_CDB)) {
> > task_cdbs++;
> > @@ -6666,11 +6836,38 @@ int transport_new_cmd_obj(
> > } else {
> > ti->ti_set_counts = 1;
> > ti->ti_dev = dev;
> > -
> > + /*
> > + * Setup any BIDI READ tasks and memory from
> > + * T_TASK(cmd)->t_mem_bidi_list so the READ struct se_tasks
> > + * are queued first..
> > + */
> > + if (cmd->data_direction == DMA_BIDIRECTIONAL) {
>
> if (T_TASK(cmd)->t_mem_bidi_list)
>
<nod>
> > + rc = transport_generic_get_cdb_count(cmd, ti,
> > + T_TASK(cmd)->t_task_lba,
> > + T_TASK(cmd)->t_tasks_sectors,
> > + DMA_FROM_DEVICE, T_TASK(cmd)->t_mem_bidi_list);
> > + if (!(rc)) {
> > + cmd->se_cmd_flags |= SCF_SCSI_CDB_EXCEPTION;
> > + cmd->scsi_sense_reason =
> > + TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
> > + return PYX_TRANSPORT_LU_COMM_FAILURE;
> > + }
> > + ti->ti_set_counts = 0;
> > + /*
> > + * Setup the DMA_TO_DEVICE direction for the next
> > + * call to transport_generic_get_cdb_count()
> > + */
> > + data_direction = DMA_TO_DEVICE;
>
> If I understand this code correctly. Then this here is wrong. You are assuming a XOR operation
> where we read some data then write some when that's finish. But other BIDI commands might be different
> they might write first then read. Or they might might read and write in parallel. Any such decisions
> should be left to the target to make. And at a per-command basis.
Ahhh OK, then I will have to signal this in struct se_cmd within
transport_generic_cmd_sequencer() depending on the type of XOR. This
will be XOR_READ_THEN_WRITE for XDWRITE_READ_10, and will add a
XOR_WRITE_THEN_READ for future CDB emulation..
>
> I know that in stgt (In user mode) the backend (what you call target, right) receives both buffers
> and decides what to do with them then calls complete.
>
> If you need any cache flushing and such. Then the DMA_TO_DEVICE main-buffer is flushed before hand
> amd the bidi_read buffer if present is flushed after-hand (or is that the other way) but the generic
> layer should no assume any ordering or execution.
>
> Please explain why you had to set the direction here. What would not happen if you did not.
The "data_direction = DMA_TO_DEVICE;" assignment here was simlpy because
of the TCM Core internal use of DMA_BIDIRECTIONAL. This will be going
away following your comments..
>
> > + } else
> > + data_direction = cmd->data_direction;
> > + /*
> > + * Setup the tasks and memory from T_TASK(cmd)->t_mem_list
> > + * Note for BIDI transfers this will contain the WRITE payload
> > + */
> > task_cdbs = transport_generic_get_cdb_count(cmd, ti,
> > T_TASK(cmd)->t_task_lba,
> > T_TASK(cmd)->t_tasks_sectors,
> > - NULL, &se_mem_out);
> > + data_direction, T_TASK(cmd)->t_mem_list);
> > if (!(task_cdbs)) {
> > cmd->se_cmd_flags |= SCF_SCSI_CDB_EXCEPTION;
> > cmd->scsi_sense_reason =
> > @@ -6743,7 +6940,17 @@ int transport_generic_get_mem(struct se_cmd *cmd, u32 length, u32 dma_size)
> >
> > T_TASK(cmd)->t_mem_list = transport_init_se_mem_list();
> > if (!(T_TASK(cmd)->t_mem_list))
> > - return -1;
> > + return -ENOMEM;
> > + /*
> > + * Setup BIDI READ list of struct se_mem elements
> > + */
> > + if (cmd->data_direction == DMA_BIDIRECTIONAL) {
>
> If (T_TASK(cmd)->t_mem_bidi_list)
> And the second check just drops
This is not setup yet, so we will need another method to signal
BIDI-COMMANDS.
>
> > + T_TASK(cmd)->t_mem_bidi_list = transport_init_se_mem_list();
> > + if (!(T_TASK(cmd)->t_mem_bidi_list)) {
> > + kfree(T_TASK(cmd)->t_mem_list);
> > + return -ENOMEM;
> > + }
> > + }
> >
> > while (length) {
> > se_mem = kmem_cache_zalloc(se_mem_cache, GFP_KERNEL);
> > @@ -7240,28 +7447,28 @@ u32 transport_generic_get_cdb_count(
> > struct se_transform_info *ti,
> > unsigned long long starting_lba,
> > u32 sectors,
> > - struct se_mem *se_mem_in,
> > - struct se_mem **se_mem_out)
> > + enum dma_data_direction data_direction,
> > + struct list_head *mem_list)
>
> Note for me:
> You moved from an se_mem * to a struct list_head *, than also added a direction.
>
> > {
> > unsigned char *cdb = NULL;
> > struct se_task *task;
> > - struct se_mem *se_mem, *se_mem_lout = NULL;
> > + struct se_mem *se_mem = NULL, *se_mem_lout = NULL;
> > struct se_device *dev = SE_DEV(cmd);
> > int max_sectors_set = 0, ret;
> > u32 task_offset_in = 0, se_mem_cnt = 0, task_cdbs = 0;
> > unsigned long long lba;
> >
> > - if (!se_mem_in) {
> > - list_for_each_entry(se_mem_in, T_TASK(cmd)->t_mem_list, se_list)
> > - break;
> > -
> > - if (!se_mem_in) {
> > - printk(KERN_ERR "se_mem_in is NULL\n");
> > - return 0;
> > - }
> > + if (!mem_list) {
> > + printk(KERN_ERR "mem_list is NULL in transport_generic_get"
> > + "_cdb_count()\n");
> > + return 0;
> > }
> > - se_mem = se_mem_in;
> > -
> > + /*
> > + * While using RAMDISK_DR backstores is the only case where
> > + * mem_list will ever be empty at this point.
> > + */
> > + if (!(list_empty(mem_list)))
> > + se_mem = list_entry(mem_list->next, struct se_mem, se_list);
> > /*
> > * Locate the start volume segment in which the received LBA will be
> > * executed upon.
> > @@ -7280,7 +7487,12 @@ u32 transport_generic_get_cdb_count(
> > CMD_TFO(cmd)->get_task_tag(cmd), lba, sectors,
> > transport_dev_end_lba(dev));
> >
> > - task = cmd->transport_get_task(ti, cmd, dev);
> > + if (!(cmd->transport_get_task)) {
> > + dump_stack();
> > + goto out;
> > + }
> > +
> > + task = cmd->transport_get_task(ti, cmd, dev, data_direction);
>
> Again this mysterious cmd->transport_get_task(). What I don't understand is if
> the transport (The transport is the fabric right? like iscsi or tcm_loop) wants
> to give you the next task to preform. Then it should know better then anybody
> what kind of command it is, No? what is the data_direction used for?
Ok, the usage of the 'transport' is really confusion here. These are
allocating struct se_task to be mapped from struct se_task->task_sg[]
and then dispatched via struct se_subsystem_api->do_task() into IBLOCK,
FILEIO, PSCSI, et al. subsystem plugin code. The reason why enum
dma_data_direction is passing this around is because the data_direction
type is currently stored in each struct se_subsystem_api I/O descriptor.
We would always add a struct se_subsystem_api->get_dma_dir() caller, but
this may be overkill. Passing the data_direction into the functions is
still a clear method I think.
>
> > if (!(task))
> > goto out;
> >
> > @@ -7293,7 +7505,7 @@ u32 transport_generic_get_cdb_count(
> > task->task_size = (task->task_sectors *
> > DEV_ATTRIB(dev)->block_size);
> > task->transport_map_task = transport_dev_get_map_SG(dev,
> > - cmd->data_direction);
> > + data_direction);
> >
> > cdb = TRANSPORT(dev)->get_cdb(task);
> > if ((cdb)) {
> > @@ -7306,14 +7518,13 @@ u32 transport_generic_get_cdb_count(
> > * Perform the SE OBJ plugin and/or Transport plugin specific
> > * mapping for T_TASK(cmd)->t_mem_list.
> > */
> > - ret = transport_do_se_mem_map(dev, task,
> > - T_TASK(cmd)->t_mem_list, NULL, se_mem,
> > - &se_mem_lout, &se_mem_cnt, &task_offset_in);
> > + ret = transport_do_se_mem_map(dev, task, mem_list,
> > + NULL, se_mem, &se_mem_lout, &se_mem_cnt,
> > + &task_offset_in);
> > if (ret < 0)
> > goto out;
> >
> > se_mem = se_mem_lout;
> > - *se_mem_out = se_mem_lout;
>
> I don't understand these changes. I'm out of context. It looks like most of them
> are not relevant to the bidi issue, and are cleanups where now you don't need
> the *se_mem_out results and it was just dropped. (Perhaps because no body used it)
> is that relevant to BIDI? Or you just took the chance of removing a parameter when
> you had to add one. (I hope the data_direction will not be needed after all)
Sorry yeah, this was one non BIDI related cleanup that was included in
the series. Please ignore.
So I will look at making the necessary changes to
lio-core-2.6.git/lio-4.0 with a follow up patch this afternoon, and
respin a BIDI new series for you to review.
Many thanks for your very helpful comments!
--nab
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