Hello Jens Axboe,
This is a semi-automatic email about new static checker warnings.
The patch 4941115bef2b: "blk-mq-tag: cleanup the normal/reserved tag
allocation" from Jan 13, 2017, leads to the following Smatch
complaint:
block/blk-mq-tag.c:142 blk_mq_get_tag()
warn: variable dereferenced before check 'data->hctx' (see line 102)
block/blk-mq-tag.c
101 {
102 struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
^^^^^^^^^^^^^^^^^^^^^^^^^^^
We added a new "data->hctx" dereference here.
103 struct sbitmap_queue *bt;
104 struct sbq_wait_state *ws;
105 DEFINE_WAIT(wait);
106 unsigned int tag_offset;
107 int tag;
108
109 if (data->flags & BLK_MQ_REQ_RESERVED) {
110 if (unlikely(!tags->nr_reserved_tags)) {
111 WARN_ON_ONCE(1);
112 return BLK_MQ_TAG_FAIL;
113 }
114 bt = &tags->breserved_tags;
115 tag_offset = 0;
116 } else {
117 bt = &tags->bitmap_tags;
118 tag_offset = tags->nr_reserved_tags;
119 }
120
121 tag = __blk_mq_get_tag(data->hctx, bt);
122 if (tag != -1)
123 goto found_tag;
124
125 if (data->flags & BLK_MQ_REQ_NOWAIT)
126 return BLK_MQ_TAG_FAIL;
127
128 ws = bt_wait_ptr(bt, data->hctx);
129 do {
130 prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE);
131
132 tag = __blk_mq_get_tag(data->hctx, bt);
133 if (tag != -1)
134 break;
135
136 /*
137 * We're out of tags on this hardware queue, kick any
138 * pending IO submits before going to sleep waiting for
139 * some to complete. Note that hctx can be NULL here for
140 * reserved tag allocation.
141 */
142 if (data->hctx)
We're in a loop here so it's possible we don't need to check the first
item in the list, but it's kind of new so I thought I would forward the
message anyway even though it might be a false positive.
143 blk_mq_run_hw_queue(data->hctx, false);
144
regards,
dan carpenter
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