Block layer patches:

- qcow2: Skip copy-on-write when allocating a zero cluster
 - qemu-img: add support for rate limit in qemu-img convert/commit
 - Fix deadlock when deleting a block node during drain_all
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Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- qcow2: Skip copy-on-write when allocating a zero cluster
- qemu-img: add support for rate limit in qemu-img convert/commit
- Fix deadlock when deleting a block node during drain_all

# gpg: Signature made Tue 27 Oct 2020 15:14:07 GMT
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream:
  block: End quiescent sections when a BDS is deleted
  qcow2: Skip copy-on-write when allocating a zero cluster
  qcow2: Report BDRV_BLOCK_ZERO more accurately in bdrv_co_block_status()
  qemu-img: add support for rate limit in qemu-img convert
  qemu-img: add support for rate limit in qemu-img commit

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

block.c

@@ -4458,6 +4458,15 @@ static void bdrv_close(BlockDriverState *bs)
     }
     QLIST_INIT(&bs->aio_notifiers);
     bdrv_drained_end(bs);
+
+    /*
+     * If we're still inside some bdrv_drain_all_begin()/end() sections, end
+     * them now since this BDS won't exist anymore when bdrv_drain_all_end()
+     * gets called.
+     */
+    if (bs->quiesce_counter) {
+        bdrv_drain_all_end_quiesce(bs);
+    }
 }
 
 void bdrv_close_all(void)

block/io.c

@@ -633,6 +633,19 @@ void bdrv_drain_all_begin(void)
     }
 }
 
+void bdrv_drain_all_end_quiesce(BlockDriverState *bs)
+{
+    int drained_end_counter = 0;
+
+    g_assert(bs->quiesce_counter > 0);
+    g_assert(!bs->refcnt);
+
+    while (bs->quiesce_counter) {
+        bdrv_do_drained_end(bs, false, NULL, true, &drained_end_counter);
+    }
+    BDRV_POLL_WHILE(bs, qatomic_read(&drained_end_counter) > 0);
+}
+
 void bdrv_drain_all_end(void)
 {
     BlockDriverState *bs = NULL;
@@ -2282,17 +2295,17 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs,
 
     if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) {
         ret |= BDRV_BLOCK_ALLOCATED;
-    } else if (want_zero && bs->drv->supports_backing) {
+    } else if (bs->drv->supports_backing) {
         BlockDriverState *cow_bs = bdrv_cow_bs(bs);
 
-        if (cow_bs) {
+        if (!cow_bs) {
+            ret |= BDRV_BLOCK_ZERO;
+        } else if (want_zero) {
             int64_t size2 = bdrv_getlength(cow_bs);
 
             if (size2 >= 0 && offset >= size2) {
                 ret |= BDRV_BLOCK_ZERO;
             }
-        } else {
-            ret |= BDRV_BLOCK_ZERO;
         }
     }
 
@@ -2447,6 +2460,33 @@ int bdrv_block_status(BlockDriverState *bs, int64_t offset, int64_t bytes,
                                    offset, bytes, pnum, map, file);
 }
 
+/*
+ * Check @bs (and its backing chain) to see if the range defined
+ * by @offset and @bytes is known to read as zeroes.
+ * Return 1 if that is the case, 0 otherwise and -errno on error.
+ * This test is meant to be fast rather than accurate so returning 0
+ * does not guarantee non-zero data.
+ */
+int coroutine_fn bdrv_co_is_zero_fast(BlockDriverState *bs, int64_t offset,
+                                      int64_t bytes)
+{
+    int ret;
+    int64_t pnum = bytes;
+
+    if (!bytes) {
+        return 1;
+    }
+
+    ret = bdrv_common_block_status_above(bs, NULL, false, false, offset,
+                                         bytes, &pnum, NULL, NULL);
+
+    if (ret < 0) {
+        return ret;
+    }
+
+    return (pnum == bytes) && (ret & BDRV_BLOCK_ZERO);
+}
+
 int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset,
                                    int64_t bytes, int64_t *pnum)
 {

block/qcow2.c

@@ -2387,26 +2387,26 @@ static bool merge_cow(uint64_t offset, unsigned bytes,
     return false;
 }
 
-static bool is_unallocated(BlockDriverState *bs, int64_t offset, int64_t bytes)
+/*
-{
+ * Return 1 if the COW regions read as zeroes, 0 if not, < 0 on error.
-    int64_t nr;
+ * Note that returning 0 does not guarantee non-zero data.
-    return !bytes ||
+ */
-        (!bdrv_is_allocated_above(bs, NULL, false, offset, bytes, &nr) &&
+static int is_zero_cow(BlockDriverState *bs, QCowL2Meta *m)
-         nr == bytes);
-}
-
-static bool is_zero_cow(BlockDriverState *bs, QCowL2Meta *m)
 {
     /*
      * This check is designed for optimization shortcut so it must be
      * efficient.
-     * Instead of is_zero(), use is_unallocated() as it is faster (but not
+     * Instead of is_zero(), use bdrv_co_is_zero_fast() as it is
-     * as accurate and can result in false negatives).
+     * faster (but not as accurate and can result in false negatives).
      */
-    return is_unallocated(bs, m->offset + m->cow_start.offset,
+    int ret = bdrv_co_is_zero_fast(bs, m->offset + m->cow_start.offset,
-                          m->cow_start.nb_bytes) &&
+                                   m->cow_start.nb_bytes);
-           is_unallocated(bs, m->offset + m->cow_end.offset,
+    if (ret <= 0) {
-                          m->cow_end.nb_bytes);
+        return ret;
+    }
+
+    return bdrv_co_is_zero_fast(bs, m->offset + m->cow_end.offset,
+                                m->cow_end.nb_bytes);
 }
 
 static int handle_alloc_space(BlockDriverState *bs, QCowL2Meta *l2meta)
@@ -2432,7 +2432,10 @@ static int handle_alloc_space(BlockDriverState *bs, QCowL2Meta *l2meta)
             continue;
         }
 
-        if (!is_zero_cow(bs, m)) {
+        ret = is_zero_cow(bs, m);
+        if (ret < 0) {
+            return ret;
+        } else if (ret == 0) {
             continue;
         }
 

docs/tools/qemu-img.rst

@@ -188,6 +188,10 @@ Parameters to convert subcommand:
   allocated target image depending on the host support for getting allocation
   information.
 
+.. option:: -r
+
+   Rate limit for the convert process
+
 .. option:: --salvage
 
   Try to ignore I/O errors when reading.  Unless in quiet mode (``-q``), errors
@@ -349,7 +353,7 @@ Command description:
   state after (the attempt at) repairing it. That is, a successful ``-r all``
   will yield the exit code 0, independently of the image state before.
 
-.. option:: commit [--object OBJECTDEF] [--image-opts] [-q] [-f FMT] [-t CACHE] [-b BASE] [-d] [-p] FILENAME
+.. option:: commit [--object OBJECTDEF] [--image-opts] [-q] [-f FMT] [-t CACHE] [-b BASE] [-r RATE_LIMIT] [-d] [-p] FILENAME
 
   Commit the changes recorded in *FILENAME* in its base image or backing file.
   If the backing file is smaller than the snapshot, then the backing file will be
@@ -371,6 +375,8 @@ Command description:
   garbage data when read. For this reason, ``-b`` implies ``-d`` (so that
   the top image stays valid).
 
+  The rate limit for the commit process is specified by ``-r``.
+
 .. option:: compare [--object OBJECTDEF] [--image-opts] [-f FMT] [-F FMT] [-T SRC_CACHE] [-p] [-q] [-s] [-U] FILENAME1 FILENAME2
 
   Check if two images have the same content. You can compare images with
@@ -408,7 +414,7 @@ Command description:
   4
     Error on reading data
 
-.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts] [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM] [-S SPARSE_SIZE] [-m NUM_COROUTINES] [-W] FILENAME [FILENAME2 [...]] OUTPUT_FILENAME
+.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts] [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM] [-S SPARSE_SIZE] [-r RATE_LIMIT] [-m NUM_COROUTINES] [-W] FILENAME [FILENAME2 [...]] OUTPUT_FILENAME
 
   Convert the disk image *FILENAME* or a snapshot *SNAPSHOT_PARAM*
   to disk image *OUTPUT_FILENAME* using format *OUTPUT_FMT*. It can

include/block/block.h

@@ -508,6 +508,8 @@ int bdrv_is_allocated(BlockDriverState *bs, int64_t offset, int64_t bytes,
 int bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
                             bool include_base, int64_t offset, int64_t bytes,
                             int64_t *pnum);
+int coroutine_fn bdrv_co_is_zero_fast(BlockDriverState *bs, int64_t offset,
+                                      int64_t bytes);
 
 bool bdrv_is_read_only(BlockDriverState *bs);
 int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
@@ -779,6 +781,12 @@ void bdrv_drained_end(BlockDriverState *bs);
  */
 void bdrv_drained_end_no_poll(BlockDriverState *bs, int *drained_end_counter);
 
+/**
+ * End all quiescent sections started by bdrv_drain_all_begin(). This is
+ * only needed when deleting a BDS before bdrv_drain_all_end() is called.
+ */
+void bdrv_drain_all_end_quiesce(BlockDriverState *bs);
+
 /**
  * End a quiescent section started by bdrv_subtree_drained_begin().
  */

qemu-img-cmds.hx

@@ -34,9 +34,9 @@ SRST
 ERST
 
 DEF("commit", img_commit,
-    "commit [--object objectdef] [--image-opts] [-q] [-f fmt] [-t cache] [-b base] [-d] [-p] filename")
+    "commit [--object objectdef] [--image-opts] [-q] [-f fmt] [-t cache] [-b base] [-r rate_limit] [-d] [-p] filename")
 SRST
-.. option:: commit [--object OBJECTDEF] [--image-opts] [-q] [-f FMT] [-t CACHE] [-b BASE] [-d] [-p] FILENAME
+.. option:: commit [--object OBJECTDEF] [--image-opts] [-q] [-f FMT] [-t CACHE] [-b BASE] [-r RATE_LIMIT] [-d] [-p] FILENAME
 ERST
 
 DEF("compare", img_compare,
@@ -46,9 +46,9 @@ SRST
 ERST
 
 DEF("convert", img_convert,
-    "convert [--object objectdef] [--image-opts] [--target-image-opts] [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T src_cache] [-O output_fmt] [-B backing_file] [-o options] [-l snapshot_param] [-S sparse_size] [-m num_coroutines] [-W] [--salvage] filename [filename2 [...]] output_filename")
+    "convert [--object objectdef] [--image-opts] [--target-image-opts] [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T src_cache] [-O output_fmt] [-B backing_file] [-o options] [-l snapshot_param] [-S sparse_size] [-r rate_limit] [-m num_coroutines] [-W] [--salvage] filename [filename2 [...]] output_filename")
 SRST
-.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts] [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM] [-S SPARSE_SIZE] [-m NUM_COROUTINES] [-W] [--salvage] FILENAME [FILENAME2 [...]] OUTPUT_FILENAME
+.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts] [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM] [-S SPARSE_SIZE] [-r RATE_LIMIT] [-m NUM_COROUTINES] [-W] [--salvage] FILENAME [FILENAME2 [...]] OUTPUT_FILENAME
 ERST
 
 DEF("create", img_create,

qemu-img.c

@@ -50,6 +50,8 @@
 #include "block/qapi.h"
 #include "crypto/init.h"
 #include "trace/control.h"
+#include "qemu/throttle.h"
+#include "block/throttle-groups.h"
 
 #define QEMU_IMG_VERSION "qemu-img version " QEMU_FULL_VERSION \
                           "\n" QEMU_COPYRIGHT "\n"
@@ -980,6 +982,7 @@ static int img_commit(int argc, char **argv)
     CommonBlockJobCBInfo cbi;
     bool image_opts = false;
     AioContext *aio_context;
+    int64_t rate_limit = 0;
 
     fmt = NULL;
     cache = BDRV_DEFAULT_CACHE;
@@ -991,7 +994,7 @@ static int img_commit(int argc, char **argv)
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, ":f:ht:b:dpq",
+        c = getopt_long(argc, argv, ":f:ht:b:dpqr:",
                         long_options, NULL);
         if (c == -1) {
             break;
@@ -1026,6 +1029,12 @@ static int img_commit(int argc, char **argv)
         case 'q':
             quiet = true;
             break;
+        case 'r':
+            rate_limit = cvtnum("rate limit", optarg);
+            if (rate_limit < 0) {
+                return 1;
+            }
+            break;
         case OPTION_OBJECT: {
             QemuOpts *opts;
             opts = qemu_opts_parse_noisily(&qemu_object_opts,
@@ -1099,7 +1108,7 @@ static int img_commit(int argc, char **argv)
 
     aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(aio_context);
-    commit_active_start("commit", bs, base_bs, JOB_DEFAULT, 0,
+    commit_active_start("commit", bs, base_bs, JOB_DEFAULT, rate_limit,
                         BLOCKDEV_ON_ERROR_REPORT, NULL, common_block_job_cb,
                         &cbi, false, &local_err);
     aio_context_release(aio_context);
@@ -1662,6 +1671,7 @@ enum ImgConvertBlockStatus {
 };
 
 #define MAX_COROUTINES 16
+#define CONVERT_THROTTLE_GROUP "img_convert"
 
 typedef struct ImgConvertState {
     BlockBackend **src;
@@ -2177,6 +2187,17 @@ static int convert_copy_bitmaps(BlockDriverState *src, BlockDriverState *dst)
 
 #define MAX_BUF_SECTORS 32768
 
+static void set_rate_limit(BlockBackend *blk, int64_t rate_limit)
+{
+    ThrottleConfig cfg;
+
+    throttle_config_init(&cfg);
+    cfg.buckets[THROTTLE_BPS_WRITE].avg = rate_limit;
+
+    blk_io_limits_enable(blk, CONVERT_THROTTLE_GROUP);
+    blk_set_io_limits(blk, &cfg);
+}
+
 static int img_convert(int argc, char **argv)
 {
     int c, bs_i, flags, src_flags = 0;
@@ -2197,6 +2218,7 @@ static int img_convert(int argc, char **argv)
     bool force_share = false;
     bool explict_min_sparse = false;
     bool bitmaps = false;
+    int64_t rate_limit = 0;
 
     ImgConvertState s = (ImgConvertState) {
         /* Need at least 4k of zeros for sparse detection */
@@ -2219,7 +2241,7 @@ static int img_convert(int argc, char **argv)
             {"bitmaps", no_argument, 0, OPTION_BITMAPS},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, ":hf:O:B:Cco:l:S:pt:T:qnm:WU",
+        c = getopt_long(argc, argv, ":hf:O:B:Cco:l:S:pt:T:qnm:WUr:",
                         long_options, NULL);
         if (c == -1) {
             break;
@@ -2316,6 +2338,12 @@ static int img_convert(int argc, char **argv)
         case 'U':
             force_share = true;
             break;
+        case 'r':
+            rate_limit = cvtnum("rate limit", optarg);
+            if (rate_limit < 0) {
+                goto fail_getopt;
+            }
+            break;
         case OPTION_OBJECT: {
             QemuOpts *object_opts;
             object_opts = qemu_opts_parse_noisily(&qemu_object_opts,
@@ -2705,6 +2733,10 @@ static int img_convert(int argc, char **argv)
         s.cluster_sectors = bdi.cluster_size / BDRV_SECTOR_SIZE;
     }
 
+    if (rate_limit) {
+        set_rate_limit(s.target, rate_limit);
+    }
+
     ret = convert_do_copy(&s);
 
     /* Now copy the bitmaps */

tests/test-bdrv-drain.c

@@ -594,6 +594,7 @@ static void test_graph_change_drain_all(void)
 
     g_assert_cmpint(bs_b->quiesce_counter, ==, 0);
     g_assert_cmpint(b_s->drain_count, ==, 0);
+    g_assert_cmpint(qemu_get_aio_context()->external_disable_cnt, ==, 0);
 
     bdrv_unref(bs_b);
     blk_unref(blk_b);