block: avoid recursive block_status call if possible

drv_co_block_status digs bs->file for additional, more accurate search
for hole inside region, reported as DATA by bs since 5daa74a6ebc.

This accuracy is not free: assume we have qcow2 disk. Actually, qcow2
knows, where are holes and where is data. But every block_status
request calls lseek additionally. Assume a big disk, full of
data, in any iterative copying block job (or img convert) we'll call
lseek(HOLE) on every iteration, and each of these lseeks will have to
iterate through all metadata up to the end of file. It's obviously
ineffective behavior. And for many scenarios we don't need this lseek
at all.

However, lseek is needed when we have metadata-preallocated image.

So, let's detect metadata-preallocation case and don't dig qcow2's
protocol file in other cases.

The idea is to compare allocation size in POV of filesystem with
allocations size in POV of Qcow2 (by refcounts). If allocation in fs is
significantly lower, consider it as metadata-preallocation case.

102 iotest changed, as our detector can't detect shrinked file as
metadata-preallocation, which don't seem to be wrong, as with metadata
preallocation we always have valid file length.

Two other iotests have a slight change in their QMP output sequence:
Active 'block-commit' returns earlier because the job coroutine yields
earlier on a blocking operation. This operation is loading the refcount
blocks in qcow2_detect_metadata_preallocation().

Suggested-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block/io.c b/block/io.c
index 3134a60a48e5d64ee96537ac31525ceab706e55a..150358c3b165bc57791fc17650d18e020a301ba9 100644 (file)
--- a/block/io.c
+++ b/block/io.c
@@ -2092,6 +2092,12 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
      */
     assert(*pnum && QEMU_IS_ALIGNED(*pnum, align) &&
            align > offset - aligned_offset);
+    if (ret & BDRV_BLOCK_RECURSE) {
+        assert(ret & BDRV_BLOCK_DATA);
+        assert(ret & BDRV_BLOCK_OFFSET_VALID);
+        assert(!(ret & BDRV_BLOCK_ZERO));
+    }
+
     *pnum -= offset - aligned_offset;
     if (*pnum > bytes) {
         *pnum = bytes;
@@ -2122,7 +2128,8 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
         }
     }
 
-    if (want_zero && local_file && local_file != bs &&
+    if (want_zero && ret & BDRV_BLOCK_RECURSE &&
+        local_file && local_file != bs &&
         (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
         (ret & BDRV_BLOCK_OFFSET_VALID)) {
         int64_t file_pnum;

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 4c1794f9af959cc47c77a4235c0e0d32474fe0f8..3a2c673a5ed42ea6e474eff5e3a8ceb73774efe5 100644 (file)
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -3444,3 +3444,35 @@ int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size)
                             "There are no references in the refcount table.");
     return -EIO;
 }
+
+int qcow2_detect_metadata_preallocation(BlockDriverState *bs)
+{
+    BDRVQcow2State *s = bs->opaque;
+    int64_t i, end_cluster, cluster_count = 0, threshold;
+    int64_t file_length, real_allocation, real_clusters;
+
+    file_length = bdrv_getlength(bs->file->bs);
+    if (file_length < 0) {
+        return file_length;
+    }
+
+    real_allocation = bdrv_get_allocated_file_size(bs->file->bs);
+    if (real_allocation < 0) {
+        return real_allocation;
+    }
+
+    real_clusters = real_allocation / s->cluster_size;
+    threshold = MAX(real_clusters * 10 / 9, real_clusters + 2);
+
+    end_cluster = size_to_clusters(s, file_length);
+    for (i = 0; i < end_cluster && cluster_count < threshold; i++) {
+        uint64_t refcount;
+        int ret = qcow2_get_refcount(bs, i, &refcount);
+        if (ret < 0) {
+            return ret;
+        }
+        cluster_count += !!refcount;
+    }
+
+    return cluster_count >= threshold;
+}

diff --git a/block/qcow2.c b/block/qcow2.c
index f2cb131048fc2bc0661bc80857d19ed688e15ff7..14f914117f8e27a8025dc386e1262620800d2ed9 100644 (file)
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1895,6 +1895,12 @@ static int coroutine_fn qcow2_co_block_status(BlockDriverState *bs,
     unsigned int bytes;
     int status = 0;
 
+    if (!s->metadata_preallocation_checked) {
+        ret = qcow2_detect_metadata_preallocation(bs);
+        s->metadata_preallocation = (ret == 1);
+        s->metadata_preallocation_checked = true;
+    }
+
     bytes = MIN(INT_MAX, count);
     qemu_co_mutex_lock(&s->lock);
     ret = qcow2_get_cluster_offset(bs, offset, &bytes, &cluster_offset);
@@ -1917,6 +1923,11 @@ static int coroutine_fn qcow2_co_block_status(BlockDriverState *bs,
     } else if (ret != QCOW2_CLUSTER_UNALLOCATED) {
         status |= BDRV_BLOCK_DATA;
     }
+    if (s->metadata_preallocation && (status & BDRV_BLOCK_DATA) &&
+        (status & BDRV_BLOCK_OFFSET_VALID))
+    {
+        status |= BDRV_BLOCK_RECURSE;
+    }
     return status;
 }
 

diff --git a/block/qcow2.h b/block/qcow2.h
index 567375e56c72c8139441c398d7950dfe90b0b83f..fc1b0d3c1e1e3110e86f36f0dcd9ded63765eac2 100644 (file)
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -356,6 +356,9 @@ typedef struct BDRVQcow2State {
     int nb_threads;
 
     BdrvChild *data_file;
+
+    bool metadata_preallocation_checked;
+    bool metadata_preallocation;
 } BDRVQcow2State;
 
 typedef struct Qcow2COWRegion {
@@ -655,6 +658,7 @@ int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order,
                                 void *cb_opaque, Error **errp);
 int qcow2_shrink_reftable(BlockDriverState *bs);
 int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size);
+int qcow2_detect_metadata_preallocation(BlockDriverState *bs);
 
 /* qcow2-cluster.c functions */
 int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,

diff --git a/include/block/block.h b/include/block/block.h
index 9b083e2bca364d9e0ceb51b7f2475b767021e6be..531cf595cf8b030729940d7cfcfb6b402f4d8616 100644 (file)
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -156,10 +156,15 @@ typedef struct HDGeometry {
  * BDRV_BLOCK_EOF: the returned pnum covers through end of file for this
  *                 layer, set by block layer
  *
- * Internal flag:
+ * Internal flags:
  * BDRV_BLOCK_RAW: for use by passthrough drivers, such as raw, to request
  *                 that the block layer recompute the answer from the returned
  *                 BDS; must be accompanied by just BDRV_BLOCK_OFFSET_VALID.
+ * BDRV_BLOCK_RECURSE: request that the block layer will recursively search for
+ *                     zeroes in file child of current block node inside
+ *                     returned region. Only valid together with both
+ *                     BDRV_BLOCK_DATA and BDRV_BLOCK_OFFSET_VALID. Should not
+ *                     appear with BDRV_BLOCK_ZERO.
  *
  * If BDRV_BLOCK_OFFSET_VALID is set, the map parameter represents the
  * host offset within the returned BDS that is allocated for the
@@ -184,6 +189,7 @@ typedef struct HDGeometry {
 #define BDRV_BLOCK_RAW          0x08
 #define BDRV_BLOCK_ALLOCATED    0x10
 #define BDRV_BLOCK_EOF          0x20
+#define BDRV_BLOCK_RECURSE      0x40
 #define BDRV_BLOCK_OFFSET_MASK  BDRV_SECTOR_MASK
 
 typedef QSIMPLEQ_HEAD(BlockReopenQueue, BlockReopenQueueEntry) BlockReopenQueue;

diff --git a/tests/qemu-iotests/102 b/tests/qemu-iotests/102
index 749ff66b8adea1d31a665efa5a85351c57331fe6..b898df436fcb7905e78e9178ef6eb2c9223e12a2 100755 (executable)
--- a/tests/qemu-iotests/102
+++ b/tests/qemu-iotests/102
@@ -55,7 +55,7 @@ $QEMU_IO -c 'write 0 64k' "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG resize -f raw --shrink "$TEST_IMG" $((5 * 64 * 1024))
 
 $QEMU_IO -c map "$TEST_IMG"
-$QEMU_IMG map "$TEST_IMG"
+$QEMU_IMG map "$TEST_IMG" | _filter_qemu_img_map
 
 echo
 echo '=== Testing map on an image file truncated outside of qemu ==='

diff --git a/tests/qemu-iotests/102.out b/tests/qemu-iotests/102.out
index 4401b08feef6d7fe4fca492b3e0a30056566aace..cd2fdc7f9650103ff35ada476c5b3a434da1b163 100644 (file)
--- a/tests/qemu-iotests/102.out
+++ b/tests/qemu-iotests/102.out
@@ -7,7 +7,8 @@ wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 Image resized.
 64 KiB (0x10000) bytes     allocated at offset 0 bytes (0x0)
-Offset          Length          Mapped to       File
+Offset          Length          File
+0               0x10000         TEST_DIR/t.IMGFMT
 
 === Testing map on an image file truncated outside of qemu ===
 

diff --git a/tests/qemu-iotests/141.out b/tests/qemu-iotests/141.out
index 41c729125845a9a549337069f30426c40946b6ab..4d71d9dcae883a95c26673bc22b19fffe5a9ba73 100644 (file)
--- a/tests/qemu-iotests/141.out
+++ b/tests/qemu-iotests/141.out
@@ -42,9 +42,9 @@ Formatting 'TEST_DIR/o.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}}
+{"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "job0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "job0", "len": 0, "offset": 0, "speed": 0, "type": "commit"}}
-{"return": {}}
 {"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: block device is in use by block job: commit"}}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "job0"}}

diff --git a/tests/qemu-iotests/144.out b/tests/qemu-iotests/144.out
index 55299201e475aaccb00e557300000892e82bca13..a9a8216beac7bb0112ce4b45364173e80bc25307 100644 (file)
--- a/tests/qemu-iotests/144.out
+++ b/tests/qemu-iotests/144.out
@@ -14,10 +14,10 @@ Formatting 'TEST_DIR/tmp.qcow2', fmt=qcow2 size=536870912 backing_file=TEST_DIR/
 
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "virtio0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "virtio0"}}
+{"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "virtio0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_READY", "data": {"device": "virtio0", "len": 0, "offset": 0, "speed": 0, "type": "commit"}}
 {"return": {}}
-{"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "virtio0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "virtio0"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "virtio0", "len": 0, "offset": 0, "speed": 0, "type": "commit"}}