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scst_vdisk: Micro-optimize the zero-copy check

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Only evaluate the SCSI command type if virt_dev->zero_copy has been
set instead of always checking the SCSI command type.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>



git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@5686 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Vladislav Bolkhovitin
2014-07-19 04:13:24 +00:00
parent 5a4571354b
commit 4e24f4f5af
1 changed files with 20 additions and 11 deletions
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31
scst/src/dev_handlers/scst_vdisk.c
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@@ -2224,6 +2224,24 @@ static int vcdrom_get_supported_opcodes(struct scst_cmd *cmd,
return 0;
}
static bool vdisk_use_zero_copy(const struct scst_cmd *cmd)
{
struct scst_vdisk_dev *virt_dev = cmd->dev->dh_priv;
if (!virt_dev->zero_copy)
return false;
switch (cmd->cdb[0]) {
case READ_6:
case READ_10:
case READ_12:
case READ_16:
return true;
}
return false;
}
/*
* Compute p->loff and p->fua.
* Returns true for success or false otherwise and set error in the commeand.
@@ -2237,7 +2255,7 @@ static bool vdisk_parse_offset(struct vdisk_cmd_params *p, struct scst_cmd *cmd)
loff_t loff;
struct scst_device *dev = cmd->dev;
struct scst_vdisk_dev *virt_dev = dev->dh_priv;
bool use_zero_copy = false, res;
bool res;
int fua = 0;
TRACE_ENTRY();
@@ -2298,15 +2316,6 @@ static bool vdisk_parse_offset(struct vdisk_cmd_params *p, struct scst_cmd *cmd)
goto out;
}
switch (opcode) {
case READ_6:
case READ_10:
case READ_12:
case READ_16:
use_zero_copy = true;
break;
}
switch (opcode) {
case WRITE_10:
case WRITE_12:
@@ -2323,7 +2332,7 @@ static bool vdisk_parse_offset(struct vdisk_cmd_params *p, struct scst_cmd *cmd)
p->loff = loff;
p->fua = fua;
p->use_zero_copy = use_zero_copy && virt_dev->zero_copy;
p->use_zero_copy = vdisk_use_zero_copy(cmd);
res = true;