| Message ID | 5afea28f.J3mbAcTR1O71tkwx%bstroesser@ts.fujitsu.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 05/18/2018 02:53 AM, Bodo Stroesser wrote: > Generally target core and TCMUser seem to work fine for tape devices and > media changers. > But there is at least one situation, where TCMUser is not able to support > sequential access device emulation correctly. > > The situation is when an initiator sends a SCSI READ CDB with a length that is > greater than the length of the tape block to read. We can distinguish two > subcases: > > A) The initiator sent the READ CDB with the SILI bit being set. > In this case the sequential access device has to transfer the data from the > tape block (only the length of the tape block) and transmit a good status. > The current interface between TCMUser and the userspace does not support > reduction of the read data size by the userspace program. > > The patch below fixes this subcase by allowing the userspace program to > specify a reduced data size in read direction. > > B) The initiator sent the READ CDB with the SILI bit not being set. > In this case the sequential access device has to transfer the data from the > tape block as in A), but additionally has to transmit CHECK CONDITION with > the ILI bit set and NO SENSE in the sensebytes. The information field in > the sensebytes must contain the residual count. > > With the below patch a user space program can specify the real read data > length and appropriate sensebytes. > TCMUser then uses the se_cmd flag SCF_TREAT_READ_AS_NORMAL, to force target > core to transmit the real data size and the sensebytes. > Note: the flag SCF_TREAT_READ_AS_NORMAL is introduced by Lee Duncan's > patch "[PATCH v4] target: transport should handle st FM/EOM/ILI reads" from > Tue, 15 May 2018 18:25:24 -0700. > > This patch was created for kernel 4.15.9. > > > Changes from RFC: > - patch now uses SCF_TREAT_READ_AS_NORMAL to fix B) also. > - comment changed accordingly > > Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com> > --- > drivers/target/target_core_user.c | 40 +++++++++++++++++++++++++++------- > include/uapi/linux/target_core_user.h | 4 ++- > 2 files changed, 35 insertions(+), 9 deletions(-) > > --- a/drivers/target/target_core_user.c > +++ b/drivers/target/target_core_user.c > @@ -576,7 +576,7 @@ static int scatter_data_area(struct tcmu > } > > static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd, > - bool bidi) > + bool bidi, uint32_t *read_len) > { > struct se_cmd *se_cmd = cmd->se_cmd; > int i, dbi; > @@ -587,6 +587,7 @@ static void gather_data_area(struct tcmu > struct page *page; > unsigned int data_nents; > uint32_t count = 0; > + uint32_t len_remaining = *read_len; > > if (!bidi) { > data_sg = se_cmd->t_data_sg; > @@ -609,7 +610,7 @@ static void gather_data_area(struct tcmu > for_each_sg(data_sg, sg, data_nents, i) { > int sg_remaining = sg->length; > to = kmap_atomic(sg_page(sg)) + sg->offset; > - while (sg_remaining > 0) { > + while (sg_remaining > 0 && len_remaining > 0) { > if (block_remaining == 0) { > if (from) > kunmap_atomic(from); > @@ -621,6 +622,7 @@ static void gather_data_area(struct tcmu > } > copy_bytes = min_t(size_t, sg_remaining, > block_remaining); > + copy_bytes = min_t(size_t, copy_bytes, len_remaining); It may just be me, but I don't like this consecutive use of min_t() to set copy_bytes. I'd prefer adding something like: if (len_remaining < copy_bytes) copy_bytes = len_remaining; but maybe I'm old-fashioned. > offset = DATA_BLOCK_SIZE - block_remaining; > tcmu_flush_dcache_range(from, copy_bytes); > memcpy(to + sg->length - sg_remaining, from + offset, > @@ -628,11 +630,15 @@ static void gather_data_area(struct tcmu > > sg_remaining -= copy_bytes; > block_remaining -= copy_bytes; > + len_remaining -= copy_bytes; > } > kunmap_atomic(to - sg->offset); > + if (len_remaining == 0) > + break; > } > if (from) > kunmap_atomic(from); > + *read_len -= len_remaining; > } > > static inline size_t spc_bitmap_free(unsigned long *bitmap, uint32_t thresh) > @@ -947,6 +953,8 @@ static void tcmu_handle_completion(struc > { > struct se_cmd *se_cmd = cmd->se_cmd; > struct tcmu_dev *udev = cmd->tcmu_dev; > + bool read_len_valid = false; > + uint32_t read_len = 0xffffffff; Why do you set read_len? Is it to make the compiler happy? Because it only gets used if read_len_valid is set, in which case it is also set, right? > > /* > * cmd has been completed already from timeout, just reclaim > @@ -961,13 +969,29 @@ static void tcmu_handle_completion(struc > pr_warn("TCMU: Userspace set UNKNOWN_OP flag on se_cmd %p\n", > cmd->se_cmd); > entry->rsp.scsi_status = SAM_STAT_CHECK_CONDITION; > - } else if (entry->rsp.scsi_status == SAM_STAT_CHECK_CONDITION) { > + goto done; > + } > + > + if ((se_cmd->se_cmd_flags & SCF_BIDI) || > + se_cmd->data_direction == DMA_FROM_DEVICE) { > + read_len_valid = (entry->hdr.uflags & TCMU_UFLAG_READ_LEN) && > + entry->rsp.read_len; > + if (read_len_valid) > + read_len = entry->rsp.read_len; Again, perhaps it's just style, but this seems harder to read than: if (uflags & READ_LEN && read_len) { read_len_valid = true; read_len = entry...read_len; } > + } > + > + if (entry->rsp.scsi_status == SAM_STAT_CHECK_CONDITION) { > transport_copy_sense_to_cmd(se_cmd, entry->rsp.sense_buffer); > - } else if (se_cmd->se_cmd_flags & SCF_BIDI) { > + if (!read_len_valid ) > + goto done; > + else > + se_cmd->se_cmd_flags |= SCF_TREAT_READ_AS_NORMAL; > + } > + if (se_cmd->se_cmd_flags & SCF_BIDI) { > /* Get Data-In buffer before clean up */ > - gather_data_area(udev, cmd, true); > + gather_data_area(udev, cmd, true, &read_len); > } else if (se_cmd->data_direction == DMA_FROM_DEVICE) { > - gather_data_area(udev, cmd, false); > + gather_data_area(udev, cmd, false, &read_len); > } else if (se_cmd->data_direction == DMA_TO_DEVICE) { > /* TODO: */ > } else if (se_cmd->data_direction != DMA_NONE) { > @@ -975,7 +999,14 @@ static void tcmu_handle_completion(struc > se_cmd->data_direction); > } > > - target_complete_cmd(cmd->se_cmd, entry->rsp.scsi_status); > +done: > + if (read_len_valid) { > + pr_debug("read_len = %d\n", read_len); > + target_complete_cmd_with_length(cmd->se_cmd, > + entry->rsp.scsi_status, read_len); > + } > + else This is just wrong. don't put the else on a separate line please. > + target_complete_cmd(cmd->se_cmd, entry->rsp.scsi_status); > > out: > cmd->se_cmd = NULL; > @@ -1532,7 +1563,7 @@ static int tcmu_configure_device(struct > /* Initialise the mailbox of the ring buffer */ > mb = udev->mb_addr; > mb->version = TCMU_MAILBOX_VERSION; > - mb->flags = TCMU_MAILBOX_FLAG_CAP_OOOC; > + mb->flags = TCMU_MAILBOX_FLAG_CAP_OOOC | TCMU_MAILBOX_FLAG_CAP_READ_LEN; > mb->cmdr_off = CMDR_OFF; > mb->cmdr_size = udev->cmdr_size; > > --- a/include/uapi/linux/target_core_user.h > +++ b/include/uapi/linux/target_core_user.h > @@ -43,6 +43,7 @@ > #define TCMU_MAILBOX_VERSION 2 > #define ALIGN_SIZE 64 /* Should be enough for most CPUs */ > #define TCMU_MAILBOX_FLAG_CAP_OOOC (1 << 0) /* Out-of-order completions */ > +#define TCMU_MAILBOX_FLAG_CAP_READ_LEN (1 << 1) /* Read data length */ > > struct tcmu_mailbox { > __u16 version; > @@ -70,6 +71,7 @@ struct tcmu_cmd_entry_hdr { > __u16 cmd_id; > __u8 kflags; > #define TCMU_UFLAG_UNKNOWN_OP 0x1 > +#define TCMU_UFLAG_READ_LEN 0x2 > __u8 uflags; > > } __packed; > @@ -118,7 +120,7 @@ struct tcmu_cmd_entry { > __u8 scsi_status; > __u8 __pad1; > __u16 __pad2; > - __u32 __pad3; > + __u32 read_len; > char sense_buffer[TCMU_SENSE_BUFFERSIZE]; > } rsp; > }; > -- > To unsubscribe from this list: send the line "unsubscribe target-devel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
--- a/drivers/target/target_core_user.c +++ b/drivers/target/target_core_user.c @@ -576,7 +576,7 @@ static int scatter_data_area(struct tcmu } static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd, - bool bidi) + bool bidi, uint32_t *read_len) { struct se_cmd *se_cmd = cmd->se_cmd; int i, dbi; @@ -587,6 +587,7 @@ static void gather_data_area(struct tcmu struct page *page; unsigned int data_nents; uint32_t count = 0; + uint32_t len_remaining = *read_len; if (!bidi) { data_sg = se_cmd->t_data_sg; @@ -609,7 +610,7 @@ static void gather_data_area(struct tcmu for_each_sg(data_sg, sg, data_nents, i) { int sg_remaining = sg->length; to = kmap_atomic(sg_page(sg)) + sg->offset; - while (sg_remaining > 0) { + while (sg_remaining > 0 && len_remaining > 0) { if (block_remaining == 0) { if (from) kunmap_atomic(from); @@ -621,6 +622,7 @@ static void gather_data_area(struct tcmu } copy_bytes = min_t(size_t, sg_remaining, block_remaining); + copy_bytes = min_t(size_t, copy_bytes, len_remaining); offset = DATA_BLOCK_SIZE - block_remaining; tcmu_flush_dcache_range(from, copy_bytes); memcpy(to + sg->length - sg_remaining, from + offset, @@ -628,11 +630,15 @@ static void gather_data_area(struct tcmu sg_remaining -= copy_bytes; block_remaining -= copy_bytes; + len_remaining -= copy_bytes; } kunmap_atomic(to - sg->offset); + if (len_remaining == 0) + break; } if (from) kunmap_atomic(from); + *read_len -= len_remaining; } static inline size_t spc_bitmap_free(unsigned long *bitmap, uint32_t thresh) @@ -947,6 +953,8 @@ static void tcmu_handle_completion(struc { struct se_cmd *se_cmd = cmd->se_cmd; struct tcmu_dev *udev = cmd->tcmu_dev; + bool read_len_valid = false; + uint32_t read_len = 0xffffffff; /* * cmd has been completed already from timeout, just reclaim @@ -961,13 +969,29 @@ static void tcmu_handle_completion(struc pr_warn("TCMU: Userspace set UNKNOWN_OP flag on se_cmd %p\n", cmd->se_cmd); entry->rsp.scsi_status = SAM_STAT_CHECK_CONDITION; - } else if (entry->rsp.scsi_status == SAM_STAT_CHECK_CONDITION) { + goto done; + } + + if ((se_cmd->se_cmd_flags & SCF_BIDI) || + se_cmd->data_direction == DMA_FROM_DEVICE) { + read_len_valid = (entry->hdr.uflags & TCMU_UFLAG_READ_LEN) && + entry->rsp.read_len; + if (read_len_valid) + read_len = entry->rsp.read_len; + } + + if (entry->rsp.scsi_status == SAM_STAT_CHECK_CONDITION) { transport_copy_sense_to_cmd(se_cmd, entry->rsp.sense_buffer); - } else if (se_cmd->se_cmd_flags & SCF_BIDI) { + if (!read_len_valid ) + goto done; + else + se_cmd->se_cmd_flags |= SCF_TREAT_READ_AS_NORMAL; + } + if (se_cmd->se_cmd_flags & SCF_BIDI) { /* Get Data-In buffer before clean up */ - gather_data_area(udev, cmd, true); + gather_data_area(udev, cmd, true, &read_len); } else if (se_cmd->data_direction == DMA_FROM_DEVICE) { - gather_data_area(udev, cmd, false); + gather_data_area(udev, cmd, false, &read_len); } else if (se_cmd->data_direction == DMA_TO_DEVICE) { /* TODO: */ } else if (se_cmd->data_direction != DMA_NONE) { @@ -975,7 +999,14 @@ static void tcmu_handle_completion(struc se_cmd->data_direction); } - target_complete_cmd(cmd->se_cmd, entry->rsp.scsi_status); +done: + if (read_len_valid) { + pr_debug("read_len = %d\n", read_len); + target_complete_cmd_with_length(cmd->se_cmd, + entry->rsp.scsi_status, read_len); + } + else + target_complete_cmd(cmd->se_cmd, entry->rsp.scsi_status); out: cmd->se_cmd = NULL; @@ -1532,7 +1563,7 @@ static int tcmu_configure_device(struct /* Initialise the mailbox of the ring buffer */ mb = udev->mb_addr; mb->version = TCMU_MAILBOX_VERSION; - mb->flags = TCMU_MAILBOX_FLAG_CAP_OOOC; + mb->flags = TCMU_MAILBOX_FLAG_CAP_OOOC | TCMU_MAILBOX_FLAG_CAP_READ_LEN; mb->cmdr_off = CMDR_OFF; mb->cmdr_size = udev->cmdr_size; --- a/include/uapi/linux/target_core_user.h +++ b/include/uapi/linux/target_core_user.h @@ -43,6 +43,7 @@ #define TCMU_MAILBOX_VERSION 2 #define ALIGN_SIZE 64 /* Should be enough for most CPUs */ #define TCMU_MAILBOX_FLAG_CAP_OOOC (1 << 0) /* Out-of-order completions */ +#define TCMU_MAILBOX_FLAG_CAP_READ_LEN (1 << 1) /* Read data length */ struct tcmu_mailbox { __u16 version; @@ -70,6 +71,7 @@ struct tcmu_cmd_entry_hdr { __u16 cmd_id; __u8 kflags; #define TCMU_UFLAG_UNKNOWN_OP 0x1 +#define TCMU_UFLAG_READ_LEN 0x2 __u8 uflags; } __packed; @@ -118,7 +120,7 @@ struct tcmu_cmd_entry { __u8 scsi_status; __u8 __pad1; __u16 __pad2; - __u32 __pad3; + __u32 read_len; char sense_buffer[TCMU_SENSE_BUFFERSIZE]; } rsp; };
Generally target core and TCMUser seem to work fine for tape devices and media changers. But there is at least one situation, where TCMUser is not able to support sequential access device emulation correctly. The situation is when an initiator sends a SCSI READ CDB with a length that is greater than the length of the tape block to read. We can distinguish two subcases: A) The initiator sent the READ CDB with the SILI bit being set. In this case the sequential access device has to transfer the data from the tape block (only the length of the tape block) and transmit a good status. The current interface between TCMUser and the userspace does not support reduction of the read data size by the userspace program. The patch below fixes this subcase by allowing the userspace program to specify a reduced data size in read direction. B) The initiator sent the READ CDB with the SILI bit not being set. In this case the sequential access device has to transfer the data from the tape block as in A), but additionally has to transmit CHECK CONDITION with the ILI bit set and NO SENSE in the sensebytes. The information field in the sensebytes must contain the residual count. With the below patch a user space program can specify the real read data length and appropriate sensebytes. TCMUser then uses the se_cmd flag SCF_TREAT_READ_AS_NORMAL, to force target core to transmit the real data size and the sensebytes. Note: the flag SCF_TREAT_READ_AS_NORMAL is introduced by Lee Duncan's patch "[PATCH v4] target: transport should handle st FM/EOM/ILI reads" from Tue, 15 May 2018 18:25:24 -0700. This patch was created for kernel 4.15.9. Changes from RFC: - patch now uses SCF_TREAT_READ_AS_NORMAL to fix B) also. - comment changed accordingly Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com> --- drivers/target/target_core_user.c | 40 +++++++++++++++++++++++++++------- include/uapi/linux/target_core_user.h | 4 ++- 2 files changed, 35 insertions(+), 9 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html