qemu

qed-check.c (6767B)

---

 /*
  * QEMU Enhanced Disk Format Consistency Check
  *
  * Copyright IBM, Corp. 2010
  *
  * Authors:
  *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
  *
  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  * See the COPYING.LIB file in the top-level directory.
  *
  */
 
 #include "qemu/osdep.h"
 #include "qed.h"
 
 typedef struct {
     BDRVQEDState *s;
     BdrvCheckResult *result;
     bool fix;                           /* whether to fix invalid offsets */
 
     uint64_t nclusters;
     uint32_t *used_clusters;            /* referenced cluster bitmap */
 
     QEDRequest request;
 } QEDCheck;
 
 static bool qed_test_bit(uint32_t *bitmap, uint64_t n) {
     return !!(bitmap[n / 32] & (1 << (n % 32)));
 }
 
 static void qed_set_bit(uint32_t *bitmap, uint64_t n) {
     bitmap[n / 32] |= 1 << (n % 32);
 }
 
 /**
  * Set bitmap bits for clusters
  *
  * @check:          Check structure
  * @offset:         Starting offset in bytes
  * @n:              Number of clusters
  */
 static bool qed_set_used_clusters(QEDCheck *check, uint64_t offset,
                                   unsigned int n)
 {
     uint64_t cluster = qed_bytes_to_clusters(check->s, offset);
     unsigned int corruptions = 0;
 
     while (n-- != 0) {
         /* Clusters should only be referenced once */
         if (qed_test_bit(check->used_clusters, cluster)) {
             corruptions++;
         }
 
         qed_set_bit(check->used_clusters, cluster);
         cluster++;
     }
 
     check->result->corruptions += corruptions;
     return corruptions == 0;
 }
 
 /**
  * Check an L2 table
  *
  * @ret:            Number of invalid cluster offsets
  */
 static unsigned int qed_check_l2_table(QEDCheck *check, QEDTable *table)
 {
     BDRVQEDState *s = check->s;
     unsigned int i, num_invalid = 0;
     uint64_t last_offset = 0;
 
     for (i = 0; i < s->table_nelems; i++) {
         uint64_t offset = table->offsets[i];
 
         if (qed_offset_is_unalloc_cluster(offset) ||
             qed_offset_is_zero_cluster(offset)) {
             continue;
         }
         check->result->bfi.allocated_clusters++;
         if (last_offset && (last_offset + s->header.cluster_size != offset)) {
             check->result->bfi.fragmented_clusters++;
         }
         last_offset = offset;
 
         /* Detect invalid cluster offset */
         if (!qed_check_cluster_offset(s, offset)) {
             if (check->fix) {
                 table->offsets[i] = 0;
                 check->result->corruptions_fixed++;
             } else {
                 check->result->corruptions++;
             }
 
             num_invalid++;
             continue;
         }
 
         qed_set_used_clusters(check, offset, 1);
     }
 
     return num_invalid;
 }
 
 /**
  * Descend tables and check each cluster is referenced once only
  */
 static int coroutine_fn qed_check_l1_table(QEDCheck *check, QEDTable *table)
 {
     BDRVQEDState *s = check->s;
     unsigned int i, num_invalid_l1 = 0;
     int ret, last_error = 0;
 
     /* Mark L1 table clusters used */
     qed_set_used_clusters(check, s->header.l1_table_offset,
                           s->header.table_size);
 
     for (i = 0; i < s->table_nelems; i++) {
         unsigned int num_invalid_l2;
         uint64_t offset = table->offsets[i];
 
         if (qed_offset_is_unalloc_cluster(offset)) {
             continue;
         }
 
         /* Detect invalid L2 offset */
         if (!qed_check_table_offset(s, offset)) {
             /* Clear invalid offset */
             if (check->fix) {
                 table->offsets[i] = 0;
                 check->result->corruptions_fixed++;
             } else {
                 check->result->corruptions++;
             }
 
             num_invalid_l1++;
             continue;
         }
 
         if (!qed_set_used_clusters(check, offset, s->header.table_size)) {
             continue; /* skip an invalid table */
         }
 
         ret = qed_read_l2_table_sync(s, &check->request, offset);
         if (ret) {
             check->result->check_errors++;
             last_error = ret;
             continue;
         }
 
         num_invalid_l2 = qed_check_l2_table(check,
                                             check->request.l2_table->table);
 
         /* Write out fixed L2 table */
         if (num_invalid_l2 > 0 && check->fix) {
             ret = qed_write_l2_table_sync(s, &check->request, 0,
                                           s->table_nelems, false);
             if (ret) {
                 check->result->check_errors++;
                 last_error = ret;
                 continue;
             }
         }
     }
 
     /* Drop reference to final table */
     qed_unref_l2_cache_entry(check->request.l2_table);
     check->request.l2_table = NULL;
 
     /* Write out fixed L1 table */
     if (num_invalid_l1 > 0 && check->fix) {
         ret = qed_write_l1_table_sync(s, 0, s->table_nelems);
         if (ret) {
             check->result->check_errors++;
             last_error = ret;
         }
     }
 
     return last_error;
 }
 
 /**
  * Check for unreferenced (leaked) clusters
  */
 static void qed_check_for_leaks(QEDCheck *check)
 {
     BDRVQEDState *s = check->s;
     uint64_t i;
 
     for (i = s->header.header_size; i < check->nclusters; i++) {
         if (!qed_test_bit(check->used_clusters, i)) {
             check->result->leaks++;
         }
     }
 }
 
 /**
  * Mark an image clean once it passes check or has been repaired
  */
 static void qed_check_mark_clean(BDRVQEDState *s, BdrvCheckResult *result)
 {
     /* Skip if there were unfixable corruptions or I/O errors */
     if (result->corruptions > 0 || result->check_errors > 0) {
         return;
     }
 
     /* Skip if image is already marked clean */
     if (!(s->header.features & QED_F_NEED_CHECK)) {
         return;
     }
 
     /* Ensure fixes reach storage before clearing check bit */
     bdrv_flush(s->bs);
 
     s->header.features &= ~QED_F_NEED_CHECK;
     qed_write_header_sync(s);
 }
 
 /* Called with table_lock held.  */
 int coroutine_fn qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix)
 {
     QEDCheck check = {
         .s = s,
         .result = result,
         .nclusters = qed_bytes_to_clusters(s, s->file_size),
         .request = { .l2_table = NULL },
         .fix = fix,
     };
     int ret;
 
     check.used_clusters = g_try_new0(uint32_t, (check.nclusters + 31) / 32);
     if (check.nclusters && check.used_clusters == NULL) {
         return -ENOMEM;
     }
 
     check.result->bfi.total_clusters =
         DIV_ROUND_UP(s->header.image_size, s->header.cluster_size);
     ret = qed_check_l1_table(&check, s->l1_table);
     if (ret == 0) {
         /* Only check for leaks if entire image was scanned successfully */
         qed_check_for_leaks(&check);
 
         if (fix) {
             qed_check_mark_clean(s, result);
         }
     }
 
     g_free(check.used_clusters);
     return ret;
 }