On 04/01/2017 01:23 AM, Bart Van Assche wrote:
Make it possible to check whether or not a block layer queue has
been stopped. Make it possible to start and to run a blk-mq queue
from user space.
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Cc: Omar Sandoval <osandov@xxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
---
Changes compared to v3:
- Return -ENOENT for attempts to run or start a queue after it has reached the
state "dead". This is needed to avoid a use-after-free and potentially a kernel
crash.
---
block/blk-mq-debugfs.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 114 insertions(+)
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 4b3f962a9c7a..bd3afa4e1602 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -43,6 +43,117 @@ static int blk_mq_debugfs_seq_open(struct inode *inode, struct file *file,
return ret;
}
+static int blk_flags_show(struct seq_file *m, const unsigned long flags,
+ const char *const *flag_name, int flag_name_count)
+{
+ bool sep = false;
+ int i;
+
+ for (i = 0; i < sizeof(flags) * BITS_PER_BYTE; i++) {
+ if (!(flags & BIT(i)))
+ continue;
+ if (sep)
+ seq_puts(m, " ");
+ sep = true;
+ if (i < flag_name_count && flag_name[i])
+ seq_puts(m, flag_name[i]);
+ else
+ seq_printf(m, "%d", i);
+ }
+ seq_puts(m, "\n");
+ return 0;
+}
+
+static const char *const blk_queue_flag_name[] = {
+ [QUEUE_FLAG_QUEUED] = "QUEUED",
+ [QUEUE_FLAG_STOPPED] = "STOPPED",
+ [QUEUE_FLAG_SYNCFULL] = "SYNCFULL",
+ [QUEUE_FLAG_ASYNCFULL] = "ASYNCFULL",
+ [QUEUE_FLAG_DYING] = "DYING",
+ [QUEUE_FLAG_BYPASS] = "BYPASS",
+ [QUEUE_FLAG_BIDI] = "BIDI",
+ [QUEUE_FLAG_NOMERGES] = "NOMERGES",
+ [QUEUE_FLAG_SAME_COMP] = "SAME_COMP",
+ [QUEUE_FLAG_FAIL_IO] = "FAIL_IO",
+ [QUEUE_FLAG_STACKABLE] = "STACKABLE",
+ [QUEUE_FLAG_NONROT] = "NONROT",
+ [QUEUE_FLAG_IO_STAT] = "IO_STAT",
+ [QUEUE_FLAG_DISCARD] = "DISCARD",
+ [QUEUE_FLAG_NOXMERGES] = "NOXMERGES",
+ [QUEUE_FLAG_ADD_RANDOM] = "ADD_RANDOM",
+ [QUEUE_FLAG_SECERASE] = "SECERASE",
+ [QUEUE_FLAG_SAME_FORCE] = "SAME_FORCE",
+ [QUEUE_FLAG_DEAD] = "DEAD",
+ [QUEUE_FLAG_INIT_DONE] = "INIT_DONE",
+ [QUEUE_FLAG_NO_SG_MERGE] = "NO_SG_MERGE",
+ [QUEUE_FLAG_POLL] = "POLL",
+ [QUEUE_FLAG_WC] = "WC",
+ [QUEUE_FLAG_FUA] = "FUA",
+ [QUEUE_FLAG_FLUSH_NQ] = "FLUSH_NQ",
+ [QUEUE_FLAG_DAX] = "DAX",
+ [QUEUE_FLAG_STATS] = "STATS",
+ [QUEUE_FLAG_POLL_STATS] = "POLL_STATS",
+ [QUEUE_FLAG_REGISTERED] = "REGISTERED",
+};
+
+static int blk_queue_flags_show(struct seq_file *m, void *v)
+{
+ struct request_queue *q = m->private;
+
+ blk_flags_show(m, q->queue_flags, blk_queue_flag_name,
+ ARRAY_SIZE(blk_queue_flag_name));
+ return 0;
+}
+
+static ssize_t blk_queue_flags_store(struct file *file, const char __user *ubuf,
+ size_t len, loff_t *offp)
+{
+ struct request_queue *q = file_inode(file)->i_private;
+ char op[16] = { }, *s;
+
+ /*
+ * The debugfs attributes are removed after blk_cleanup_queue() has
+ * called blk_mq_free_queue(). Return if QUEUE_FLAG_DEAD has been set
+ * to avoid triggering a use-after-free.
+ */
+ if (blk_queue_dead(q))
+ return -ENOENT;
+
+ len = min(len, sizeof(op) - 1);
+ if (copy_from_user(op, ubuf, len))
+ return -EFAULT;
+ s = op;
+ strsep(&s, " \t\n"); /* strip trailing whitespace */
+ if (strcmp(op, "run") == 0) {
+ blk_mq_run_hw_queues(q, true);
+ } else if (strcmp(op, "start") == 0) {
+ blk_mq_start_stopped_hw_queues(q, true);
+ } else {
+ pr_err("%s: unsupported operation %s. Use either 'run' or 'start'\n",
+ __func__, op);
+ return -EINVAL;
+ }
+ return len;
+}
+
I would have added 'stop' for completeness, but that's probably for very
specific cases only.
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Cheers,
Hannes
