[Qemu-devel] [RFC V2 17/20] qcow2: Integrate deduplication in qcow2_co_writev loop.

["Benoît Canet" <benoit@irqsave.net>]

---
 block/qcow2.c |   79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 78 insertions(+), 1 deletion(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index c6879ea..e0c1a68 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -330,6 +330,7 @@ static int qcow2_open(BlockDriverState *bs, int flags)
     QCowHeader header;
     uint64_t ext_end;
 
+    s->has_dedup = false;
     ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
     if (ret < 0) {
         goto fail;
@@ -812,6 +813,12 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState *bs,
     QEMUIOVector hd_qiov;
     uint64_t bytes_done = 0;
     uint8_t *cluster_data = NULL;
+    uint8_t *dedup_cluster_data = NULL;
+    uint8_t *next_call_first_hash;
+    int dedup_cluster_data_nr;
+    int deduped_sectors_nr;
+    int skip_before_dedup_clusters_nr;
+    int next_non_dedupable_sectors_nr;
     QCowL2Meta l2meta = {
         .nb_clusters = 0,
     };
@@ -827,11 +834,66 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState *bs,
 
     qemu_co_mutex_lock(&s->lock);
 
+    if (s->has_dedup) {
+        /* if deduplication is on we make sure dedup_cluster_data
+         * contains a multiple of cluster size of data in order
+         * to compute the hashes
+         */
+        ret = qcow2_dedup_read_missing_and_concatenate(bs,
+                                                       qiov,
+                                                       sector_num,
+                                                       remaining_sectors,
+                                                       &dedup_cluster_data,
+                                                       &dedup_cluster_data_nr);
+
+        if (ret < 0) {
+            goto fail;
+        }
+    }
+
+    next_call_first_hash = NULL;
+    next_non_dedupable_sectors_nr = 0;
+    skip_before_dedup_clusters_nr = 0;
     while (remaining_sectors != 0) {
 
         trace_qcow2_writev_start_part(qemu_coroutine_self());
+
+        if (s->has_dedup && next_non_dedupable_sectors_nr == 0) {
+            /* Try to deduplicate as much clusters as possible */
+            deduped_sectors_nr = qcow2_dedup(bs,
+                                             sector_num,
+                                             dedup_cluster_data,
+                                             dedup_cluster_data_nr,
+                                             &skip_before_dedup_clusters_nr,
+                                             &next_non_dedupable_sectors_nr,
+                                             &next_call_first_hash);
+
+            remaining_sectors -= deduped_sectors_nr;
+            sector_num += deduped_sectors_nr;
+            bytes_done += deduped_sectors_nr * 512;
+
+            /* no more data to write -> exit
+             * Can be < 0 because of the presence of sectors we read in
+             * qcow2_read_missing_dedup_sectors_and_concatenate.
+             */
+            if (next_non_dedupable_sectors_nr <= 0) {
+                goto fail;
+            }
+
+            /* if we deduped something trace it */
+            if (deduped_sectors_nr) {
+                trace_qcow2_writev_done_part(qemu_coroutine_self(),
+                                             deduped_sectors_nr);
+                trace_qcow2_writev_start_part(qemu_coroutine_self());
+            }
+        }
+
         index_in_cluster = sector_num & (s->cluster_sectors - 1);
-        n_end = index_in_cluster + remaining_sectors;
+        n_end = s->has_dedup &&
+                next_non_dedupable_sectors_nr < remaining_sectors ?
+                index_in_cluster + next_non_dedupable_sectors_nr :
+                index_in_cluster + remaining_sectors;
+
         if (s->crypt_method &&
             n_end > QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors) {
             n_end = QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors;
@@ -873,6 +935,19 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState *bs,
                 cur_nr_sectors * 512);
         }
 
+        /* Write the non duplicated clusters hashes to disk
+         * just before writing non duplicated data.
+         */
+        if (s->has_dedup) {
+            ret = qcow2_dedup_write_new_hashes(bs,
+                                               (cluster_offset >> 9),
+                                               cur_nr_sectors /
+                                               s->cluster_sectors);
+            if (ret < 0) {
+                goto fail;
+            }
+        }
+
         BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
         qemu_co_mutex_unlock(&s->lock);
         trace_qcow2_writev_data(qemu_coroutine_self(),
@@ -892,6 +967,7 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState *bs,
 
         run_dependent_requests(s, &l2meta);
 
+        next_non_dedupable_sectors_nr -= cur_nr_sectors;
         remaining_sectors -= cur_nr_sectors;
         sector_num += cur_nr_sectors;
         bytes_done += cur_nr_sectors * 512;
@@ -906,6 +982,7 @@ fail:
 
     qemu_iovec_destroy(&hd_qiov);
     qemu_vfree(cluster_data);
+    qemu_vfree(dedup_cluster_data);
     trace_qcow2_writev_done_req(qemu_coroutine_self(), ret);
 
     return ret;
-- 
1.7.10.4