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

[Max Reitz <mreitz@redhat.com>]

Am 30.08.2013 10:48, schrieb Kevin Wolf:
> 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. ;-)
Okay, I'll do that.

>> +            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.
Oh, right. I keep forgetting preallocations… :-/

>> +
>> +            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.
Okay.

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

Max