On 01/30/2013 02:57 PM, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
>
> This patch allows IBLOCK to check block hints in request_queue->flush_flags
> when reporting current backend device WriteCacheEnabled status to a remote
> SCSI initiator port.
>
> This is done via a se_subsystem_api->get_write_cache() call instead of a
> backend se_device creation time flag, as we expect REQ_FLUSH bits to possibly
> change from an underlying blk_queue_flush() by the SCSI disk driver, or
> internal raw struct block_device driver usage.
>
> Also go ahead and update iblock_execute_rw() bio I/O path code to use
> REQ_FLUSH + REQ_FUA hints when determining WRITE_FUA usage, and make SPC
> emulation code use a spc_check_dev_wce() helper to handle both types of
> cases for virtual backend subsystem drivers.
>
> Reported-by: majianpeng <majianpeng@xxxxxxxxx>
> Cc: majianpeng <majianpeng@xxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> Cc: James Bottomley <JBottomley@xxxxxxxxxxxxx>
> Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> ---
> drivers/target/target_core_device.c | 6 ++++++
> drivers/target/target_core_iblock.c | 31 +++++++++++++++++++++++--------
> drivers/target/target_core_spc.c | 21 ++++++++++++++++++---
> include/target/target_core_backend.h | 1 +
> 4 files changed, 48 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
> index e269510..1d71930 100644
> --- a/drivers/target/target_core_device.c
> +++ b/drivers/target/target_core_device.c
> @@ -772,6 +772,12 @@ int se_dev_set_emulate_write_cache(struct se_device *dev, int flag)
> pr_err("emulate_write_cache not supported for pSCSI\n");
> return -EINVAL;
> }
> + if (dev->transport->get_write_cache != NULL) {
one nit:
if (dev->transport->get_write_cache) {
?
> + pr_warn("emulate_write_cache cannot be changed when underlying"
> + " HW reports WriteCacheEnabled, ignoring request\n");
> + return 0;
> + }
> +
> dev->dev_attrib.emulate_write_cache = flag;
> pr_debug("dev[%p]: SE Device WRITE_CACHE_EMULATION flag: %d\n",
> dev, dev->dev_attrib.emulate_write_cache);
> diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
> index b526d23..fc45683 100644
> --- a/drivers/target/target_core_iblock.c
> +++ b/drivers/target/target_core_iblock.c
> @@ -154,6 +154,7 @@ static int iblock_configure_device(struct se_device *dev)
>
> if (blk_queue_nonrot(q))
> dev->dev_attrib.is_nonrot = 1;
> +
> return 0;
>
> out_free_bioset:
> @@ -654,20 +655,24 @@ iblock_execute_rw(struct se_cmd *cmd)
> u32 sg_num = sgl_nents;
> sector_t block_lba;
> unsigned bio_cnt;
> - int rw;
> + int rw = 0;
> int i;
>
> if (data_direction == DMA_TO_DEVICE) {
> + struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
> + struct request_queue *q = bdev_get_queue(ib_dev->ibd_bd);
> /*
> - * Force data to disk if we pretend to not have a volatile
> - * write cache, or the initiator set the Force Unit Access bit.
> + * Force writethrough using WRITE_FUA if a volatile write cache
> + * is not enabled, or if initiator set the Force Unit Access bit.
> */
> - if (dev->dev_attrib.emulate_write_cache == 0 ||
> - (dev->dev_attrib.emulate_fua_write > 0 &&
> - (cmd->se_cmd_flags & SCF_FUA)))
> - rw = WRITE_FUA;
> - else
> + if (q->flush_flags & REQ_FUA) {
> + if (cmd->se_cmd_flags & SCF_FUA)
> + rw = WRITE_FUA;
> + else if (!(q->flush_flags & REQ_FLUSH))
> + rw = WRITE_FUA;
> + } else {
> rw = WRITE;
> + }
> } else {
> rw = READ;
> }
> @@ -774,6 +779,15 @@ iblock_parse_cdb(struct se_cmd *cmd)
> return sbc_parse_cdb(cmd, &iblock_sbc_ops);
> }
>
> +bool iblock_get_write_cache(struct se_device *dev)
> +{
> + struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
> + struct block_device *bd = ib_dev->ibd_bd;
> + struct request_queue *q = bdev_get_queue(bd);
> +
> + return (q->flush_flags & REQ_FLUSH);
no need of the ().
> +}
> +
> static struct se_subsystem_api iblock_template = {
> .name = "iblock",
> .inquiry_prod = "IBLOCK",
> @@ -790,6 +804,7 @@ static struct se_subsystem_api iblock_template = {
> .show_configfs_dev_params = iblock_show_configfs_dev_params,
> .get_device_type = sbc_get_device_type,
> .get_blocks = iblock_get_blocks,
> + .get_write_cache = iblock_get_write_cache,
> };
>
> static int __init iblock_module_init(void)
> diff --git a/drivers/target/target_core_spc.c b/drivers/target/target_core_spc.c
> index 1346f8a..db6d003 100644
> --- a/drivers/target/target_core_spc.c
> +++ b/drivers/target/target_core_spc.c
> @@ -407,16 +407,31 @@ check_scsi_name:
> }
> EXPORT_SYMBOL(spc_emulate_evpd_83);
>
> +static bool
> +spc_check_dev_wce(struct se_device *dev)
> +{
> + bool wce = false;
> +
> + if (dev->transport->get_write_cache)
> + wce = dev->transport->get_write_cache(dev);
> + else if (dev->dev_attrib.emulate_write_cache > 0)
> + wce = true;
> +
> + return wce;
> +}
> +
> /* Extended INQUIRY Data VPD Page */
> static sense_reason_t
> spc_emulate_evpd_86(struct se_cmd *cmd, unsigned char *buf)
> {
> + struct se_device *dev = cmd->se_dev;
> +
> buf[3] = 0x3c;
> /* Set HEADSUP, ORDSUP, SIMPSUP */
> buf[5] = 0x07;
>
> /* If WriteCache emulation is enabled, set V_SUP */
> - if (cmd->se_dev->dev_attrib.emulate_write_cache > 0)
> + if (spc_check_dev_wce(dev))
> buf[6] = 0x01;
> return 0;
> }
> @@ -767,7 +782,7 @@ static int spc_modesense_caching(struct se_device *dev, u8 pc, u8 *p)
> if (pc == 1)
> goto out;
>
> - if (dev->dev_attrib.emulate_write_cache > 0)
> + if (spc_check_dev_wce(dev))
> p[2] = 0x04; /* Write Cache Enable */
> p[12] = 0x20; /* Disabled Read Ahead */
>
> @@ -897,7 +912,7 @@ static sense_reason_t spc_emulate_modesense(struct se_cmd *cmd)
> (cmd->se_deve->lun_flags & TRANSPORT_LUNFLAGS_READ_ONLY)))
> spc_modesense_write_protect(&buf[length], type);
>
> - if ((dev->dev_attrib.emulate_write_cache > 0) &&
> + if ((spc_check_dev_wce(dev)) &&
> (dev->dev_attrib.emulate_fua_write > 0))
> spc_modesense_dpofua(&buf[length], type);
>
> diff --git a/include/target/target_core_backend.h b/include/target/target_core_backend.h
> index 819b0fc..f9a8016 100644
> --- a/include/target/target_core_backend.h
> +++ b/include/target/target_core_backend.h
> @@ -35,6 +35,7 @@ struct se_subsystem_api {
> u32 (*get_device_type)(struct se_device *);
> sector_t (*get_blocks)(struct se_device *);
> unsigned char *(*get_sense_buffer)(struct se_cmd *);
> + bool (*get_write_cache)(struct se_device *);
> };
>
> struct sbc_ops {
>
--
Asias
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