xref: /qemu/block/qed-check.c (revision 6402cbbb) 
1 /*
2  * QEMU Enhanced Disk Format Consistency Check
3  *
4  * Copyright IBM, Corp. 2010
5  *
6  * Authors:
7  *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
8  *
9  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
10  * See the COPYING.LIB file in the top-level directory.
11  *
12  */
13 
14 #include "qemu/osdep.h"
15 #include "qed.h"
16 
17 typedef struct {
18     BDRVQEDState *s;
19     BdrvCheckResult *result;
20     bool fix;                           /* whether to fix invalid offsets */
21 
22     uint64_t nclusters;
23     uint32_t *used_clusters;            /* referenced cluster bitmap */
24 
25     QEDRequest request;
26 } QEDCheck;
27 
28 static bool qed_test_bit(uint32_t *bitmap, uint64_t n) {
29     return !!(bitmap[n / 32] & (1 << (n % 32)));
30 }
31 
32 static void qed_set_bit(uint32_t *bitmap, uint64_t n) {
33     bitmap[n / 32] |= 1 << (n % 32);
34 }
35 
36 /**
37  * Set bitmap bits for clusters
38  *
39  * @check:          Check structure
40  * @offset:         Starting offset in bytes
41  * @n:              Number of clusters
42  */
43 static bool qed_set_used_clusters(QEDCheck *check, uint64_t offset,
44                                   unsigned int n)
45 {
46     uint64_t cluster = qed_bytes_to_clusters(check->s, offset);
47     unsigned int corruptions = 0;
48 
49     while (n-- != 0) {
50         /* Clusters should only be referenced once */
51         if (qed_test_bit(check->used_clusters, cluster)) {
52             corruptions++;
53         }
54 
55         qed_set_bit(check->used_clusters, cluster);
56         cluster++;
57     }
58 
59     check->result->corruptions += corruptions;
60     return corruptions == 0;
61 }
62 
63 /**
64  * Check an L2 table
65  *
66  * @ret:            Number of invalid cluster offsets
67  */
68 static unsigned int qed_check_l2_table(QEDCheck *check, QEDTable *table)
69 {
70     BDRVQEDState *s = check->s;
71     unsigned int i, num_invalid = 0;
72     uint64_t last_offset = 0;
73 
74     for (i = 0; i < s->table_nelems; i++) {
75         uint64_t offset = table->offsets[i];
76 
77         if (qed_offset_is_unalloc_cluster(offset) ||
78             qed_offset_is_zero_cluster(offset)) {
79             continue;
80         }
81         check->result->bfi.allocated_clusters++;
82         if (last_offset && (last_offset + s->header.cluster_size != offset)) {
83             check->result->bfi.fragmented_clusters++;
84         }
85         last_offset = offset;
86 
87         /* Detect invalid cluster offset */
88         if (!qed_check_cluster_offset(s, offset)) {
89             if (check->fix) {
90                 table->offsets[i] = 0;
91                 check->result->corruptions_fixed++;
92             } else {
93                 check->result->corruptions++;
94             }
95 
96             num_invalid++;
97             continue;
98         }
99 
100         qed_set_used_clusters(check, offset, 1);
101     }
102 
103     return num_invalid;
104 }
105 
106 /**
107  * Descend tables and check each cluster is referenced once only
108  */
109 static int qed_check_l1_table(QEDCheck *check, QEDTable *table)
110 {
111     BDRVQEDState *s = check->s;
112     unsigned int i, num_invalid_l1 = 0;
113     int ret, last_error = 0;
114 
115     /* Mark L1 table clusters used */
116     qed_set_used_clusters(check, s->header.l1_table_offset,
117                           s->header.table_size);
118 
119     for (i = 0; i < s->table_nelems; i++) {
120         unsigned int num_invalid_l2;
121         uint64_t offset = table->offsets[i];
122 
123         if (qed_offset_is_unalloc_cluster(offset)) {
124             continue;
125         }
126 
127         /* Detect invalid L2 offset */
128         if (!qed_check_table_offset(s, offset)) {
129             /* Clear invalid offset */
130             if (check->fix) {
131                 table->offsets[i] = 0;
132                 check->result->corruptions_fixed++;
133             } else {
134                 check->result->corruptions++;
135             }
136 
137             num_invalid_l1++;
138             continue;
139         }
140 
141         if (!qed_set_used_clusters(check, offset, s->header.table_size)) {
142             continue; /* skip an invalid table */
143         }
144 
145         ret = qed_read_l2_table_sync(s, &check->request, offset);
146         if (ret) {
147             check->result->check_errors++;
148             last_error = ret;
149             continue;
150         }
151 
152         num_invalid_l2 = qed_check_l2_table(check,
153                                             check->request.l2_table->table);
154 
155         /* Write out fixed L2 table */
156         if (num_invalid_l2 > 0 && check->fix) {
157             ret = qed_write_l2_table_sync(s, &check->request, 0,
158                                           s->table_nelems, false);
159             if (ret) {
160                 check->result->check_errors++;
161                 last_error = ret;
162                 continue;
163             }
164         }
165     }
166 
167     /* Drop reference to final table */
168     qed_unref_l2_cache_entry(check->request.l2_table);
169     check->request.l2_table = NULL;
170 
171     /* Write out fixed L1 table */
172     if (num_invalid_l1 > 0 && check->fix) {
173         ret = qed_write_l1_table_sync(s, 0, s->table_nelems);
174         if (ret) {
175             check->result->check_errors++;
176             last_error = ret;
177         }
178     }
179 
180     return last_error;
181 }
182 
183 /**
184  * Check for unreferenced (leaked) clusters
185  */
186 static void qed_check_for_leaks(QEDCheck *check)
187 {
188     BDRVQEDState *s = check->s;
189     uint64_t i;
190 
191     for (i = s->header.header_size; i < check->nclusters; i++) {
192         if (!qed_test_bit(check->used_clusters, i)) {
193             check->result->leaks++;
194         }
195     }
196 }
197 
198 /**
199  * Mark an image clean once it passes check or has been repaired
200  */
201 static void qed_check_mark_clean(BDRVQEDState *s, BdrvCheckResult *result)
202 {
203     /* Skip if there were unfixable corruptions or I/O errors */
204     if (result->corruptions > 0 || result->check_errors > 0) {
205         return;
206     }
207 
208     /* Skip if image is already marked clean */
209     if (!(s->header.features & QED_F_NEED_CHECK)) {
210         return;
211     }
212 
213     /* Ensure fixes reach storage before clearing check bit */
214     bdrv_flush(s->bs);
215 
216     s->header.features &= ~QED_F_NEED_CHECK;
217     qed_write_header_sync(s);
218 }
219 
220 int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix)
221 {
222     QEDCheck check = {
223         .s = s,
224         .result = result,
225         .nclusters = qed_bytes_to_clusters(s, s->file_size),
226         .request = { .l2_table = NULL },
227         .fix = fix,
228     };
229     int ret;
230 
231     check.used_clusters = g_try_new0(uint32_t, (check.nclusters + 31) / 32);
232     if (check.nclusters && check.used_clusters == NULL) {
233         return -ENOMEM;
234     }
235 
236     check.result->bfi.total_clusters =
237         DIV_ROUND_UP(s->header.image_size, s->header.cluster_size);
238     ret = qed_check_l1_table(&check, s->l1_table);
239     if (ret == 0) {
240         /* Only check for leaks if entire image was scanned successfully */
241         qed_check_for_leaks(&check);
242 
243         if (fix) {
244             qed_check_mark_clean(s, result);
245         }
246     }
247 
248     g_free(check.used_clusters);
249     return ret;
250 }
251