[PATCH v6 4/5] parallels: Add checking and repairing duplicate offsets in BAT

[Alexander Ivanov]

Cluster offsets must be unique among all the BAT entries. Find duplicate
offsets in the BAT and fix it by copying the content of the relevant
cluster to a newly allocated cluster and set the new cluster offset to the
duplicated entry.

Add host_cluster_index() helper to deduplicate the code.

When new clusters are allocated, the file size increases by 128 Mb. Call
parallels_check_leak() to fix this leak.

Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
---
 block/parallels.c | 142 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)

diff --git a/block/parallels.c b/block/parallels.c
index 78a34bd667..d507fe7d90 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -136,6 +136,12 @@ static int cluster_remainder(BDRVParallelsState *s, 
int64_t sector_num,
     return MIN(nb_sectors, ret);
 }
 
+static uint32_t host_cluster_index(BDRVParallelsState *s, int64_t off)
+{
+    off -= le32_to_cpu(s->header->data_off) << BDRV_SECTOR_BITS;
+    return off / s->cluster_size;
+}
+
 static int64_t block_status(BDRVParallelsState *s, int64_t sector_num,
                             int nb_sectors, int *pnum)
 {
@@ -528,6 +534,137 @@ parallels_check_leak(BlockDriverState *bs, 
BdrvCheckResult *res,
     return 0;
 }
 
+static int parallels_check_duplicate(BlockDriverState *bs,
+                                     BdrvCheckResult *res,
+                                     BdrvCheckMode fix)
+{
+    BDRVParallelsState *s = bs->opaque;
+    int64_t off, sector;
+    unsigned long *bitmap;
+    uint32_t i, bitmap_size, cluster_index, old_offset;
+    int n, ret = 0;
+    uint64_t *buf = NULL;
+    bool fixed = false;
+
+    /*
+     * Create a bitmap of used clusters.
+     * If a bit is set, there is a BAT entry pointing to this cluster.
+     * Loop through the BAT entries, check bits relevant to an entry offset.
+     * If bit is set, this entry is duplicated. Otherwise set the bit.
+     *
+     * We shouldn't worry about newly allocated clusters outside the image
+     * because they are created higher then any existing cluster pointed by
+     * a BAT entry.
+     */
+    bitmap_size = host_cluster_index(s, res->image_end_offset);
+    if (bitmap_size == 0) {
+        return 0;
+    }
+
+    bitmap = bitmap_new(bitmap_size);
+
+    buf = qemu_blockalign(bs, s->cluster_size);
+
+    for (i = 0; i < s->bat_size; i++) {
+        off = bat2sect(s, i) << BDRV_SECTOR_BITS;
+        if (off == 0) {
+            continue;
+        }
+
+        cluster_index = host_cluster_index(s, off);
+        assert(cluster_index < bitmap_size);
+        if (test_bit(cluster_index, bitmap)) {
+            /* this cluster duplicates another one */
+            fprintf(stderr,
+                    "%s duplicate offset in BAT entry %u\n",
+                    fix & BDRV_FIX_ERRORS ? "Repairing" : "ERROR", i);
+
+            res->corruptions++;
+
+            if (fix & BDRV_FIX_ERRORS) {
+                /*
+                 * Reset the entry and allocate a new cluster
+                 * for the relevant guest offset. In this way we let
+                 * the lower layer to place the new cluster properly.
+                 * Copy the original cluster to the allocated one.
+                 * But before save the old offset value for repairing
+                 * if we have an error.
+                 */
+                old_offset = le32_to_cpu(s->bat_bitmap[i]);
+                parallels_set_bat_entry(s, i, 0);
+
+                ret = bdrv_co_pread(bs->file, off, s->cluster_size, buf, 0);
+                if (ret < 0) {
+                    res->check_errors++;
+                    goto out_repare_bat;
+                }
+
+                sector = i * (int64_t)s->tracks;
+                sector = allocate_clusters(bs, sector, s->tracks, &n);
+                if (sector < 0) {
+                    res->check_errors++;
+                    ret = sector;
+                    goto out_repare_bat;
+                }
+                off = sector << BDRV_SECTOR_BITS;
+
+                ret = bdrv_co_pwrite(bs->file, off, s->cluster_size, buf, 0);
+                if (ret < 0) {
+                    res->check_errors++;
+                    goto out_repare_bat;
+                }
+
+                if (off + s->cluster_size > res->image_end_offset) {
+                    res->image_end_offset = off + s->cluster_size;
+                }
+
+                /*
+                 * In the future allocate_cluster() will reuse holed offsets
+                 * inside the image. Keep the used clusters bitmap content
+                 * consistent for the new allocated clusters too.
+                 *
+                 * Note, clusters allocated outside the current image are not
+                 * considered, and the bitmap size doesn't change.
+                 */
+                cluster_index = host_cluster_index(s, off);
+                if (cluster_index < bitmap_size) {
+                    bitmap_set(bitmap, cluster_index, 1);
+                }
+
+                fixed = true;
+                res->corruptions_fixed++;
+            }
+        } else {
+            bitmap_set(bitmap, cluster_index, 1);
+        }
+    }
+
+    if (fixed) {
+        /*
+         * When new clusters are allocated, the file size increases by
+         * 128 Mb. We need to truncate the file to the right size. Let
+         * the leak fix code make its job without res changing.
+         */
+        ret = parallels_check_leak(bs, res, fix, false);
+        if (ret < 0) {
+            goto out;
+        }
+    }
+    goto out;
+
+/*
+ * We can get here only from places where index and old_offset have
+ * meaningful values.
+ */
+out_repare_bat:
+    s->bat_bitmap[i] = cpu_to_le32(old_offset);
+
+out:
+    g_free(buf);
+    g_free(bitmap);
+    return ret;
+}
+
 static void parallels_collect_statistics(BlockDriverState *bs,
                                          BdrvCheckResult *res,
                                          BdrvCheckMode fix)
@@ -579,6 +716,11 @@ parallels_co_check(BlockDriverState *bs, BdrvCheckResult 
*res,
             return ret;
         }
 
+        ret = parallels_check_duplicate(bs, res, fix);
+        if (ret < 0) {
+            return ret;
+        }
+
         parallels_collect_statistics(bs, res, fix);
     }
 
-- 
2.34.1