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target/iblock: Use backend REQ_FLUSH hint for WriteCacheEnabled status 

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.

(asias: Drop unnecessary comparsion operators)

Reported-by: majianpeng <majianpeng@gmail.com>
Cc: majianpeng <majianpeng@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Nicholas Bellinger 2013-01-29 22:10:06 -08:00
parent 1be2956d30
commit d0c8b259f8
4 changed files with 48 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/target/target_core_device.c
View File

@ -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) {
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);

31
drivers/target/target_core_iblock.c
View File

@ -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;
}
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)

21
drivers/target/target_core_spc.c
View File

@ -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;
}
@ -766,7 +781,7 @@ 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 */
@ -878,7 +893,7 @@ 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);

1
include/target/target_core_backend.h
View File

@ -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 {