[ Sorry, I don't know why Smatch is complaining about two year old code.
The warning is valid enough, though. - dan ]
Hello Matthew Auld,
The patch 14d1b9a6247c: "drm/i915: buddy allocator" from Aug 9, 2019,
leads to the following static checker warning:
drivers/gpu/drm/i915/selftests/i915_buddy.c:169 igt_check_blocks()
warn: variable dereferenced before check 'block' (see line 126)
drivers/gpu/drm/i915/selftests/i915_buddy.c
111 static int igt_check_blocks(struct i915_buddy_mm *mm,
112 struct list_head *blocks,
113 u64 expected_size,
114 bool is_contiguous)
115 {
116 struct i915_buddy_block *block;
117 struct i915_buddy_block *prev;
118 u64 total;
119 int err = 0;
120
121 block = NULL;
122 prev = NULL;
123 total = 0;
124
125 list_for_each_entry(block, blocks, link) {
^^^^^
"block" is the list iterator so it can't be NULL.
126 err = igt_check_block(mm, block);
127
128 if (!i915_buddy_block_is_allocated(block)) {
129 pr_err("block not allocated\n"),
130 err = -EINVAL;
131 }
132
133 if (is_contiguous && prev) {
134 u64 prev_block_size;
135 u64 prev_offset;
136 u64 offset;
137
138 prev_offset = i915_buddy_block_offset(prev);
139 prev_block_size = i915_buddy_block_size(mm, prev);
140 offset = i915_buddy_block_offset(block);
141
142 if (offset != (prev_offset + prev_block_size)) {
143 pr_err("block offset mismatch\n");
144 err = -EINVAL;
145 }
146 }
147
148 if (err)
149 break;
150
151 total += i915_buddy_block_size(mm, block);
152 prev = block;
153 }
154
155 if (!err) {
156 if (total != expected_size) {
157 pr_err("size mismatch, expected=%llx, found=%llx\n",
158 expected_size, total);
159 err = -EINVAL;
160 }
161 return err;
162 }
163
164 if (prev) {
165 pr_err("prev block, dump:\n");
166 igt_dump_block(mm, prev);
167 }
168
169 if (block) {
^^^^^
This is impossible. It's not clear what was intended...
170 pr_err("bad block, dump:\n");
171 igt_dump_block(mm, block);
172 }
173
174 return err;
175 }
regards,
dan carpenter
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