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Add some conditional code to handle kernel versions less that 2.6.25 that

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can send a request as a non scatterlist. If we get one, we create a single
element scatterlist and hand that on to SCST. 

This costs some extra space in the structure I use to keep track of requests
and the done function, but only on those versions for which it is possible.
For real kernels it is scatterlists all the way down young man.



git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@922 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Richard Sharpe
2009-06-26 00:54:57 +00:00
parent 6f5bc12172
commit dc78e8a39c
1 changed files with 58 additions and 18 deletions
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76
scst_local/scst_local.c
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@@ -143,10 +143,16 @@ struct scst_local_host_info {
/*
* Maintains data that is needed during command processing ...
* We have a single element scatterlist in here in case the scst_cmnd
* we are given has a buffer, not a scatterlist, but we only need this for
* kernels less than 2.6.25.
*/
struct scst_local_tgt_specific {
struct scsi_cmnd *cmnd;
void (*done)(struct scsi_cmnd *);
#if (LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 25))
struct scatterlist sgl;
#endif
};
/*
@@ -451,6 +457,8 @@ static int scst_local_queuecommand(struct scsi_cmnd *SCpnt,
{
struct scst_local_tgt_specific *tgt_specific = NULL;
struct scst_local_host_info *scst_lcl_host;
struct scatterlist *sgl = NULL;
int sgl_count = 0;
int target = SCpnt->device->id;
int lun;
struct scst_cmd *scst_cmd = NULL;
@@ -506,19 +514,64 @@ static int scst_local_queuecommand(struct scsi_cmnd *SCpnt,
break;
}
/*
* Get some memory to keep track of the cmnd and the done routine
*/
tgt_specific = kmem_cache_alloc(tgt_specific_pool, GFP_ATOMIC);
if (!tgt_specific) {
printk(KERN_ERR "%s out of memory at line %d\n",
__func__, __LINE__);
return -ENOMEM;
}
tgt_specific->cmnd = SCpnt;
tgt_specific->done = done;
/*
* If the command has a request, not a scatterlist, then convert it
* to one. We use scsi_sg_count to isolate us from the changes from
* version to version
*/
#if (LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 25))
if (scsi_sg_count(SCpnt)) {
sgl = scsi_sglist(SCpnt);
sgl_count = scsi_sg_count(SCpnt);
} else {
/*
* Build a one-element scatter list out of the buffer
* We will not even get here if the kernel version we
* are building on only supports scatterlists. See #if above.
*
* We use the sglist and bufflen function/macros to isolate
* us from kernel version differences.
*/
if (scsi_sglist(SCpnt)) {
sg_init_one(&(tgt_specific->sgl),
(const void *)scsi_sglist(SCpnt),
scsi_bufflen(SCpnt));
sgl = &(tgt_specific->sgl);
sgl_count = 1;
}
else {
sgl = NULL;
sgl_count = 0;
}
}
#else
sgl = scsi_sglist(SCpnt);
sgl_count = scsi_sg_count(SCpnt);
#endif
dir = SCST_DATA_NONE;
switch (SCpnt->sc_data_direction) {
case DMA_TO_DEVICE:
dir = SCST_DATA_WRITE;
scst_cmd_set_expected(scst_cmd, dir, scsi_bufflen(SCpnt));
scst_cmd_set_tgt_sg(scst_cmd, scsi_sglist(SCpnt),
scsi_sg_count(SCpnt));
scst_cmd_set_tgt_sg(scst_cmd, sgl, sgl_count);
break;
case DMA_FROM_DEVICE:
dir = SCST_DATA_READ;
scst_cmd_set_expected(scst_cmd, dir, scsi_bufflen(SCpnt));
scst_cmd_set_tgt_sg(scst_cmd, scsi_sglist(SCpnt),
scsi_sg_count(SCpnt));
scst_cmd_set_tgt_sg(scst_cmd, sgl, sgl_count);
break;
case DMA_BIDIRECTIONAL:
#if (LINUX_VERSION_CODE > KERNEL_VERSION(2, 6, 24))
@@ -527,8 +580,7 @@ static int scst_local_queuecommand(struct scsi_cmnd *SCpnt,
scst_cmd_set_expected(scst_cmd, dir, scsi_bufflen(SCpnt));
scst_cmd_set_expected_in_transfer_len(scst_cmd,
scsi_in(SCpnt)->length);
scst_cmd_set_tgt_sg(scst_cmd, scsi_sglist(SCpnt),
scsi_sg_count(SCpnt));
scst_cmd_set_tgt_sg(scst_cmd, sgl, sgl_count);
scst_cmd_set_tgt_in_sg(scst_cmd, scsi_in(SCpnt)->table.sgl,
scsi_in(SCpnt)->table.nents);
break;
@@ -540,18 +592,6 @@ static int scst_local_queuecommand(struct scsi_cmnd *SCpnt,
break;
}
/*
* Defer allocating memory until all error paths are done
*/
tgt_specific = kmem_cache_alloc(tgt_specific_pool, GFP_ATOMIC);
if (!tgt_specific) {
printk(KERN_ERR "%s out of memory at line %d\n",
__func__, __LINE__);
return -ENOMEM;
}
tgt_specific->cmnd = SCpnt;
tgt_specific->done = done;
scst_cmd_set_tgt_priv(scst_cmd, tgt_specific);
#ifdef CONFIG_SCST_LOCAL_FORCE_DIRECT_PROCESSING