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target/qla2xxx: Honor max_data_sg_nents I/O transfer limit

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This patch adds an optional fabric driver provided SGL limit
that target-core will honor as it's own internal I/O maximum
transfer length limit, as exposed by EVPD=0xb0 block limits
parameters.

This is required for handling cases when host I/O transfer
length exceeds the requested EVPD block limits maximum
transfer length. The initial user of this logic is qla2xxx,
so that we can avoid having to reject I/Os from some legacy
FC hosts where EVPD=0xb0 parameters are not honored.

When se_cmd payload length exceeds the provided limit in
target_check_max_data_sg_nents() code, se_cmd->data_length +
se_cmd->prot_length are reset with se_cmd->residual_count
plus underflow bit for outgoing TFO response callbacks.
It also checks for existing CDB level underflow + overflow
and recalculates final residual_count as necessary.

Note this patch currently assumes 1:1 mapping of PAGE_SIZE
per struct scatterlist entry.

Reported-by: Craig Watson <[email protected]>
Cc: Craig Watson <[email protected]>
Tested-by: Himanshu Madhani <[email protected]>
Cc: Roland Dreier <[email protected]>
Cc: Arun Easi <[email protected]>
Cc: Giridhar Malavali <[email protected]>
Cc: Andrew Vasquez <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Martin K. Petersen <[email protected]>
Signed-off-by: Nicholas Bellinger <[email protected]>
This commit is contained in:
Nicholas Bellinger 2015-07-30 18:28:13 -07:00
commit 8f9b565482
4 changed files with 78 additions and 4 deletions
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13
drivers/target/target_core_spc.c
View file

@ -477,8 +477,8 @@ static sense_reason_t
spc_emulate_evpd_b0(struct se_cmd *cmd, unsigned char *buf)
{
struct se_device *dev = cmd->se_dev;
int have_tp = 0;
int opt, min;
u32 mtl = 0;
int have_tp = 0, opt, min;
/*
* Following spc3r22 section 6.5.3 Block Limits VPD page, when
@ -509,8 +509,15 @@ spc_emulate_evpd_b0(struct se_cmd *cmd, unsigned char *buf)
/*
* Set MAXIMUM TRANSFER LENGTH
*
* XXX: Currently assumes single PAGE_SIZE per scatterlist for fabrics
* enforcing maximum HW scatter-gather-list entry limit
*/
put_unaligned_be32(dev->dev_attrib.hw_max_sectors, &buf[8]);
if (cmd->se_tfo->max_data_sg_nents) {
mtl = (cmd->se_tfo->max_data_sg_nents * PAGE_SIZE) /
dev->dev_attrib.block_size;
}
put_unaligned_be32(min_not_zero(mtl, dev->dev_attrib.hw_max_sectors), &buf[8]);
/*
* Set OPTIMAL TRANSFER LENGTH

51
drivers/target/target_core_transport.c
View file

@ -1075,6 +1075,55 @@ transport_set_vpd_ident(struct t10_vpd *vpd, unsigned char *page_83)
}
EXPORT_SYMBOL(transport_set_vpd_ident);
static sense_reason_t
target_check_max_data_sg_nents(struct se_cmd *cmd, struct se_device *dev,
unsigned int size)
{
u32 mtl;
if (!cmd->se_tfo->max_data_sg_nents)
return TCM_NO_SENSE;
/*
* Check if fabric enforced maximum SGL entries per I/O descriptor
* exceeds se_cmd->data_length. If true, set SCF_UNDERFLOW_BIT +
* residual_count and reduce original cmd->data_length to maximum
* length based on single PAGE_SIZE entry scatter-lists.
*/
mtl = (cmd->se_tfo->max_data_sg_nents * PAGE_SIZE);
if (cmd->data_length > mtl) {
/*
* If an existing CDB overflow is present, calculate new residual
* based on CDB size minus fabric maximum transfer length.
*
* If an existing CDB underflow is present, calculate new residual
* based on original cmd->data_length minus fabric maximum transfer
* length.
*
* Otherwise, set the underflow residual based on cmd->data_length
* minus fabric maximum transfer length.
*/
if (cmd->se_cmd_flags & SCF_OVERFLOW_BIT) {
cmd->residual_count = (size - mtl);
} else if (cmd->se_cmd_flags & SCF_UNDERFLOW_BIT) {
u32 orig_dl = size + cmd->residual_count;
cmd->residual_count = (orig_dl - mtl);
} else {
cmd->se_cmd_flags |= SCF_UNDERFLOW_BIT;
cmd->residual_count = (cmd->data_length - mtl);
}
cmd->data_length = mtl;
/*
* Reset sbc_check_prot() calculated protection payload
* length based upon the new smaller MTL.
*/
if (cmd->prot_length) {
u32 sectors = (mtl / dev->dev_attrib.block_size);
cmd->prot_length = dev->prot_length * sectors;
}
}
return TCM_NO_SENSE;
}
sense_reason_t
target_cmd_size_check(struct se_cmd *cmd, unsigned int size)
{
@ -1120,7 +1169,7 @@ target_cmd_size_check(struct se_cmd *cmd, unsigned int size)
}
}
return 0;
return target_check_max_data_sg_nents(cmd, dev, size);
}