On Wed, 2013-01-30 at 15:39 +0800, Asias He wrote:
> On 01/30/2013 02:57 PM, Nicholas A. Bellinger wrote:
> > From: Nicholas Bellinger <n...@linux-iscsi.org>
> >
> > 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 <majianp...@gmail.com>
> > Cc: majianpeng <majianp...@gmail.com>
> > Cc: Christoph Hellwig <h...@infradead.org>
> > Cc: Jens Axboe <ax...@kernel.dk>
> > Cc: James Bottomley <jbottom...@parallels.com>
> > Signed-off-by: Nicholas Bellinger <n...@linux-iscsi.org>
> > ---
> > 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) {
>
> ?
Dropping extra NULL comparison here.
>
> > + 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 ().
>
Dropping unnecessary () for bit-wise comparison.
Thanks Asias!
--nab
> > +}
> > +
> > 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 {
> >
>
>
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