Re: [Qemu-devel] [PATCH v3 4/8] qcow2-refcount: Move OFLAG_COPIED checks

[Kevin Wolf <kwolf@redhat.com>]

Am 30.08.2013 um 09:46 hat Max Reitz geschrieben:
> Move the OFLAG_COPIED checks out of check_refcounts_l1 and
> check_refcounts_l2 and after the actual refcount checks/fixes (since the
> refcounts might actually change there).
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qcow2-refcount.c | 99 +++++++++++++++++++++++++++++++++-----------------
>  1 file changed, 65 insertions(+), 34 deletions(-)
> 
> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> index 310efcc..fdc0f86 100644
> --- a/block/qcow2-refcount.c
> +++ b/block/qcow2-refcount.c
> @@ -1035,7 +1035,7 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
>      BDRVQcowState *s = bs->opaque;
>      uint64_t *l2_table, l2_entry;
>      uint64_t next_contiguous_offset = 0;
> -    int i, l2_size, nb_csectors, refcount;
> +    int i, l2_size, nb_csectors;
>  
>      /* Read L2 table from disk */
>      l2_size = s->l2_size * sizeof(uint64_t);
> @@ -1087,23 +1087,8 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
>  
>          case QCOW2_CLUSTER_NORMAL:
>          {
> -            /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
>              uint64_t offset = l2_entry & L2E_OFFSET_MASK;
>  
> -            if (flags & CHECK_OFLAG_COPIED) {
> -                refcount = get_refcount(bs, offset >> s->cluster_bits);
> -                if (refcount < 0) {
> -                    fprintf(stderr, "Can't get refcount for offset %"
> -                        PRIx64 ": %s\n", l2_entry, strerror(-refcount));
> -                    goto fail;
> -                }
> -                if ((refcount == 1) != ((l2_entry & QCOW_OFLAG_COPIED) != 0)) {
> -                    fprintf(stderr, "ERROR OFLAG_COPIED: offset=%"
> -                        PRIx64 " refcount=%d\n", l2_entry, refcount);
> -                    res->corruptions++;
> -                }
> -            }
> -
>              if (flags & CHECK_FRAG_INFO) {
>                  res->bfi.allocated_clusters++;
>                  if (next_contiguous_offset &&
> @@ -1160,7 +1145,7 @@ static int check_refcounts_l1(BlockDriverState *bs,
>  {
>      BDRVQcowState *s = bs->opaque;
>      uint64_t *l1_table, l2_offset, l1_size2;
> -    int i, refcount, ret;
> +    int i, ret;
>  
>      l1_size2 = l1_size * sizeof(uint64_t);
>  
> @@ -1184,22 +1169,6 @@ static int check_refcounts_l1(BlockDriverState *bs,
>      for(i = 0; i < l1_size; i++) {
>          l2_offset = l1_table[i];
>          if (l2_offset) {
> -            /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
> -            if (flags & CHECK_OFLAG_COPIED) {
> -                refcount = get_refcount(bs, (l2_offset & ~QCOW_OFLAG_COPIED)
> -                    >> s->cluster_bits);
> -                if (refcount < 0) {
> -                    fprintf(stderr, "Can't get refcount for l2_offset %"
> -                        PRIx64 ": %s\n", l2_offset, strerror(-refcount));
> -                    goto fail;
> -                }
> -                if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) {
> -                    fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64
> -                        " refcount=%d\n", l2_offset, refcount);
> -                    res->corruptions++;
> -                }
> -            }
> -
>              /* Mark L2 table as used */
>              l2_offset &= L1E_OFFSET_MASK;
>              inc_refcounts(bs, res, refcount_table, refcount_table_size,
> @@ -1241,7 +1210,8 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
>  {
>      BDRVQcowState *s = bs->opaque;
>      int64_t size, i, highest_cluster;
> -    int nb_clusters, refcount1, refcount2;
> +    uint64_t *l2_table = NULL;
> +    int nb_clusters, refcount1, refcount2, j;
>      QCowSnapshot *sn;
>      uint16_t *refcount_table;
>      int ret;
> @@ -1365,10 +1335,71 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
>          }
>      }
>  
> +    l2_table = qemu_blockalign(bs, s->cluster_size);
> +
> +    /* check OFLAG_COPIED */
> +    for (i = 0; i < s->l1_size; i++) {
> +        uint64_t l1_entry = s->l1_table[i];
> +        uint64_t l2_offset = l1_entry & L1E_OFFSET_MASK;
> +        int refcount;
> +
> +        if (!l2_offset) {
> +            continue;
> +        }
> +
> +        refcount = get_refcount(bs, l2_offset >> s->cluster_bits);
> +        if (refcount < 0) {
> +            /* don't print message nor increment check_errors, since the above
> +             * loop will have done this already */
> +            continue;
> +        }
> +        if ((refcount == 1) != ((l1_entry & QCOW_OFLAG_COPIED) != 0)) {
> +            fprintf(stderr, "ERROR OFLAG_COPIED L2 cluster: l1_entry=%" PRIx64
> +                    " refcount=%d\n",
> +                    l1_entry, refcount);

In theory, code motion patches shouldn't change much else, but as you're
already changing the message here, I wouldn't mind if you also sneaked
in the L1 index. ;-)

> +            res->corruptions++;
> +        }
> +
> +        ret = bdrv_pread(bs->file, l2_offset, l2_table,
> +                s->l2_size * sizeof(uint64_t));

Indentation: s would usually be aligned to the same column as bs.

> +        if (ret < 0) {
> +            fprintf(stderr, "ERROR: Could not read L2 table: %s\n",
> +                    strerror(-ret));
> +            res->check_errors++;
> +            goto fail;
> +        }
> +
> +        for (j = 0; j < s->l2_size; j++) {
> +            uint64_t l2_entry = be64_to_cpu(l2_table[j]);
> +            uint64_t data_offset;
> +
> +            if (qcow2_get_cluster_type(l2_entry) != QCOW2_CLUSTER_NORMAL) {
> +                continue;
> +            }

You're removing the check for QCOW2_CLUSTER_ZERO, which was a
fall-through case in the original code.

> +
> +            data_offset = l2_entry & L2E_OFFSET_MASK;
> +
> +            refcount = get_refcount(bs, data_offset >> s->cluster_bits);
> +            if (refcount < 0) {
> +                /* don't print message nor increment check_errors, since the
> +                 * above loop will have done this already */
> +                continue;
> +            }
> +            if ((refcount == 1) != ((l2_entry & QCOW_OFLAG_COPIED) != 0)) {
> +                fprintf(stderr, "ERROR OFLAG_COPIED data cluster: l2_entry=%"
> +                        PRIx64 " refcount=%d\n",
> +                        l2_entry, refcount);
> +                res->corruptions++;
> +            }
> +        }
> +    }

I think it's long enough that it deserves a separate function.

> +
>      res->image_end_offset = (highest_cluster + 1) * s->cluster_size;
>      ret = 0;
>  
>  fail:
> +    qemu_vfree(l2_table);
>      g_free(refcount_table);
>  
>      return ret;

Kevin