Hello Sami Tolvanen,
The patch a739ff3f543a: "dm verity: add support for forward error
correction" from Dec 3, 2015, leads to the following static checker
warning:
drivers/md/dm-verity-fec.c:147 fec_decode_bufs()
warn: 'par' can also be NULL
drivers/md/dm-verity-fec.c
128 static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio,
129 u64 rsb, int byte_index, unsigned block_offset,
130 int neras)
131 {
132 int r, corrected = 0, res;
133 struct dm_buffer *buf;
134 unsigned n, i, offset;
135 u8 *par, *block;
136
137 par = fec_read_parity(v, rsb, block_offset, &offset, &buf);
138 if (IS_ERR(par))
139 return PTR_ERR(par);
Apparently, if the read is a blocking read then new_read() returns NULL.
The documentation is unclear (just joking, there is no documentation).
140
141 /*
142 * Decode the RS blocks we have in bufs. Each RS block results in
143 * one corrected target byte and consumes fec->roots parity bytes.
144 */
145 fec_for_each_buffer_rs_block(fio, n, i) {
146 block = fec_buffer_rs_block(v, fio, n, i);
147 res = fec_decode_rs8(v, fio, block, &par[offset], neras);
148 if (res < 0) {
149 r = res;
150 goto error;
151 }
152
153 corrected += res;
154 fio->output[block_offset] = block[byte_index];
155
156 block_offset++;
157 if (block_offset >= 1 << v->data_dev_block_bits)
158 goto done;
159
160 /* read the next block when we run out of parity bytes */
161 offset += v->fec->roots;
162 if (offset >= 1 << v->data_dev_block_bits) {
163 dm_bufio_release(buf);
164
165 par = fec_read_parity(v, rsb, block_offset, &offset, &buf);
166 if (unlikely(IS_ERR(par)))
167 return PTR_ERR(par);
168 }
169 }
170 done:
171 r = corrected;
regards,
dan carpenter
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