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authorMikulas Patocka <mpatocka@redhat.com>2013-03-01 22:45:49 +0000
committerAlasdair G Kergon <agk@redhat.com>2013-03-01 22:45:49 +0000
commita26062416ef8add48f16fbadded2b5f6fb84d024 (patch)
tree4f960c51bd22d99e55a1f56cf28f86f018de01a3
parent02cde50b7ea74557d32ff778c73809322445ccd2 (diff)
dm ioctl: allow message to return data
This patch introduces enhanced message support that allows the device-mapper core to recognise messages that are common to all devices, and for messages to return data to userspace. Core messages are processed by the function "message_for_md". If the device mapper doesn't support the message, it is passed to the target driver. If the message returns data, the kernel sets the flag DM_MESSAGE_OUT_FLAG. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
-rw-r--r--drivers/md/dm-ioctl.c36
-rw-r--r--include/uapi/linux/dm-ioctl.h5
2 files changed, 40 insertions, 1 deletions
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 7eb0682d574f..aa04f0224642 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1414,6 +1414,22 @@ static int table_status(struct dm_ioctl *param, size_t param_size)
return 0;
}
+static bool buffer_test_overflow(char *result, unsigned maxlen)
+{
+ return !maxlen || strlen(result) + 1 >= maxlen;
+}
+
+/*
+ * Process device-mapper dependent messages.
+ * Returns a number <= 1 if message was processed by device mapper.
+ * Returns 2 if message should be delivered to the target.
+ */
+static int message_for_md(struct mapped_device *md, unsigned argc, char **argv,
+ char *result, unsigned maxlen)
+{
+ return 2;
+}
+
/*
* Pass a message to the target that's at the supplied device offset.
*/
@@ -1425,6 +1441,8 @@ static int target_message(struct dm_ioctl *param, size_t param_size)
struct dm_table *table;
struct dm_target *ti;
struct dm_target_msg *tmsg = (void *) param + param->data_start;
+ size_t maxlen;
+ char *result = get_result_buffer(param, param_size, &maxlen);
md = find_device(param);
if (!md)
@@ -1448,6 +1466,10 @@ static int target_message(struct dm_ioctl *param, size_t param_size)
goto out_argv;
}
+ r = message_for_md(md, argc, argv, result, maxlen);
+ if (r <= 1)
+ goto out_argv;
+
table = dm_get_live_table(md);
if (!table)
goto out_argv;
@@ -1473,7 +1495,18 @@ static int target_message(struct dm_ioctl *param, size_t param_size)
out_argv:
kfree(argv);
out:
- param->data_size = 0;
+ if (r >= 0)
+ __dev_status(md, param);
+
+ if (r == 1) {
+ param->flags |= DM_DATA_OUT_FLAG;
+ if (buffer_test_overflow(result, maxlen))
+ param->flags |= DM_BUFFER_FULL_FLAG;
+ else
+ param->data_size = param->data_start + strlen(result) + 1;
+ r = 0;
+ }
+
dm_put(md);
return r;
}
@@ -1653,6 +1686,7 @@ static int validate_params(uint cmd, struct dm_ioctl *param)
param->flags &= ~DM_BUFFER_FULL_FLAG;
param->flags &= ~DM_UEVENT_GENERATED_FLAG;
param->flags &= ~DM_SECURE_DATA_FLAG;
+ param->flags &= ~DM_DATA_OUT_FLAG;
/* Ignores parameters */
if (cmd == DM_REMOVE_ALL_CMD ||
diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index b8a6bddf0727..7e75b6fd8d45 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -336,4 +336,9 @@ enum {
*/
#define DM_SECURE_DATA_FLAG (1 << 15) /* In */
+/*
+ * If set, a message generated output data.
+ */
+#define DM_DATA_OUT_FLAG (1 << 16) /* Out */
+
#endif /* _LINUX_DM_IOCTL_H */