target: Fix task count > 1 handling breakage and use max_sector page alignment
This patch addresses recent breakage with multiple se_task (task_count > 1)
operation following backend dev->se_sub_dev->se_dev_attrib.max_sectors in new
transport_allocate_data_tasks() code. The initial bug here was a bogus
task->task_sg_nents assignment in transport_allocate_data_tasks() based on
the passed parameter, which now uses DIV_ROUND_UP(task_size, PAGE_SIZE) to
determine the proper number of per task SGL entries for the (task_count > 1)
case.
This also means we now need to enforce a PAGE_SIZE aligned max_sector count
value for this to work as expected without bringing back the pre v3.1
transport_map_mem_to_sg() logic to handle SGL offsets across multiple tasks.
So this patch adds se_dev_align_max_sectors() to round down max_sectors as
necessary to ensure this alignment via se_dev_set_default_attribs() and
se_dev_align_max_sectors() and keeps it simple for (task_count > 1)
operation.
So far this bugfix has been tested with (task_count > 1) operation
using iscsi-target and iblock backends.
Reported-by: Chris Boot <bootc@bootc.net>
Cc: Kiran Patil <kiran.patil@intel.com>
Cc: Andy Grover <agrover@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index ec3fbcd..4b5237f 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -839,6 +839,24 @@
return ret;
}
+u32 se_dev_align_max_sectors(u32 max_sectors, u32 block_size)
+{
+ u32 tmp, aligned_max_sectors;
+ /*
+ * Limit max_sectors to a PAGE_SIZE aligned value for modern
+ * transport_allocate_data_tasks() operation.
+ */
+ tmp = rounddown((max_sectors * block_size), PAGE_SIZE);
+ aligned_max_sectors = (tmp / block_size);
+ if (max_sectors != aligned_max_sectors) {
+ printk(KERN_INFO "Rounding down aligned max_sectors from %u"
+ " to %u\n", max_sectors, aligned_max_sectors);
+ return aligned_max_sectors;
+ }
+
+ return max_sectors;
+}
+
void se_dev_set_default_attribs(
struct se_device *dev,
struct se_dev_limits *dev_limits)
@@ -878,6 +896,11 @@
* max_sectors is based on subsystem plugin dependent requirements.
*/
dev->se_sub_dev->se_dev_attrib.hw_max_sectors = limits->max_hw_sectors;
+ /*
+ * Align max_sectors down to PAGE_SIZE to follow transport_allocate_data_tasks()
+ */
+ limits->max_sectors = se_dev_align_max_sectors(limits->max_sectors,
+ limits->logical_block_size);
dev->se_sub_dev->se_dev_attrib.max_sectors = limits->max_sectors;
/*
* Set optimal_sectors from max_sectors, which can be lowered via
@@ -1242,6 +1265,11 @@
return -EINVAL;
}
}
+ /*
+ * Align max_sectors down to PAGE_SIZE to follow transport_allocate_data_tasks()
+ */
+ max_sectors = se_dev_align_max_sectors(max_sectors,
+ dev->se_sub_dev->se_dev_attrib.block_size);
dev->se_sub_dev->se_dev_attrib.max_sectors = max_sectors;
pr_debug("dev[%p]: SE Device max_sectors changed to %u\n",
