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target: support zero-size allocation lengths in transport_kmap_data_sg 

In order to support zero-size allocation lengths, do not assert
that we have a scatterlist until after checking cmd->data_length.

But once we do this, we can have two cases of transport_kmap_data_sg
returning NULL: a zero-size allocation length, or an out-of-memory
condition.  Report the latter using sense codes, so that the SCSI
command that triggered it will fail.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Paolo Bonzini 2012-09-07 17:30:35 +02:00 committed by Nicholas Bellinger
parent 9b16b9edb4
commit 3717ef0c63
1 changed files with 9 additions and 4 deletions
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13
drivers/target/target_core_transport.c
View File

@ -2190,7 +2190,6 @@ void *transport_kmap_data_sg(struct se_cmd *cmd)
struct page **pages;
int i;
BUG_ON(!sg);
/*
* We need to take into account a possible offset here for fabrics like
* tcm_loop who may be using a contig buffer from the SCSI midlayer for
@ -2198,13 +2197,17 @@ void *transport_kmap_data_sg(struct se_cmd *cmd)
*/
if (!cmd->t_data_nents)
return NULL;
else if (cmd->t_data_nents == 1)
BUG_ON(!sg);
if (cmd->t_data_nents == 1)
return kmap(sg_page(sg)) + sg->offset;
/* >1 page. use vmap */
pages = kmalloc(sizeof(*pages) * cmd->t_data_nents, GFP_KERNEL);
if (!pages)
if (!pages) {
cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
return NULL;
}
/* convert sg[] to pages[] */
for_each_sg(cmd->t_data_sg, sg, cmd->t_data_nents, i) {
@ -2213,8 +2216,10 @@ void *transport_kmap_data_sg(struct se_cmd *cmd)
cmd->t_data_vmap = vmap(pages, cmd->t_data_nents, VM_MAP, PAGE_KERNEL);
kfree(pages);
if (!cmd->t_data_vmap)
if (!cmd->t_data_vmap) {
cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
return NULL;
}
return cmd->t_data_vmap + cmd->t_data_sg[0].offset;
}