[Qemu-devel] [RFC PATCH 08/17] block: kill the write zeroes operation

[Paolo Bonzini <pbonzini@redhat.com>]

They do not provide anything more than the discard operations now.
Remove them, and use discard instead in qemu-io and the tests.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block.c                    |   17 +--------------
 block.h                    |   15 ++++++-------
 qemu-io.c                  |   50 +-------------------------------------------
 tests/qemu-iotests/031     |    6 ++--
 tests/qemu-iotests/031.out |    4 +-
 5 files changed, 14 insertions(+), 78 deletions(-)

diff --git a/block.c b/block.c
index 30b137f..af73497 100644
--- a/block.c
+++ b/block.c
@@ -50,7 +50,6 @@
 
 typedef enum {
     BDRV_REQ_COPY_ON_READ = 0x1,
-    BDRV_REQ_ZERO_WRITE   = 0x2,
 } BdrvRequestFlags;
 
 static void bdrv_dev_change_media_cb(BlockDriverState *bs, bool load);
@@ -1849,12 +1848,7 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
     }
 
     tracked_request_begin(&req, bs, sector_num, nb_sectors, true);
-
-    if (flags & BDRV_REQ_ZERO_WRITE) {
-        ret = bdrv_co_do_write_zeroes(bs, sector_num, nb_sectors, qiov);
-    } else {
-        ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);
-    }
+    ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);
 
     if (bs->dirty_bitmap) {
         set_dirty_bitmap(bs, sector_num, nb_sectors, 1);
@@ -1877,15 +1871,6 @@ int coroutine_fn bdrv_co_writev(BlockDriverState *bs, int64_t sector_num,
     return bdrv_co_do_writev(bs, sector_num, nb_sectors, qiov, 0);
 }
 
-int coroutine_fn bdrv_co_write_zeroes(BlockDriverState *bs,
-                                      int64_t sector_num, int nb_sectors)
-{
-    trace_bdrv_co_write_zeroes(bs, sector_num, nb_sectors);
-
-    return bdrv_co_do_writev(bs, sector_num, nb_sectors, NULL,
-                             BDRV_REQ_ZERO_WRITE);
-}
-
 /**
  * Truncate file to 'offset' bytes (needed only for file protocols)
  */
diff --git a/block.h b/block.h
index 7feda73..ef07bb0 100644
--- a/block.h
+++ b/block.h
@@ -151,14 +151,6 @@ int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,
     int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
 int coroutine_fn bdrv_co_writev(BlockDriverState *bs, int64_t sector_num,
     int nb_sectors, QEMUIOVector *qiov);
-/*
- * Efficiently zero a region of the disk image.  Note that this is a regular
- * I/O request like read or write and should have a reasonable size.  This
- * function is not suitable for zeroing the entire image in a single request
- * because it may allocate memory for the entire region.
- */
-int coroutine_fn bdrv_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
-    int nb_sectors);
 int coroutine_fn bdrv_co_is_allocated(BlockDriverState *bs, int64_t sector_num,
     int nb_sectors, int *pnum);
 BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
@@ -196,6 +188,13 @@ BlockDriverAIOCB *bdrv_aio_writev(BlockDriverState *bs, int64_t sector_num,
                                   BlockDriverCompletionFunc *cb, void *opaque);
 BlockDriverAIOCB *bdrv_aio_flush(BlockDriverState *bs,
                                  BlockDriverCompletionFunc *cb, void *opaque);
+
+/*
+ * Efficiently zero a region of the disk image.  Note that this is a regular
+ * I/O request like read or write and should have a reasonable size.  This
+ * function is not suitable for zeroing the entire image in a single request
+ * because it may allocate memory for the entire region.
+ */
 BlockDriverAIOCB *bdrv_aio_discard(BlockDriverState *bs,
                                    int64_t sector_num, int nb_sectors,
                                    BlockDriverCompletionFunc *cb, void *opaque);
diff --git a/qemu-io.c b/qemu-io.c
index 8f28b6a..bb5f7b8 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -218,51 +218,6 @@ static int do_pwrite(char *buf, int64_t offset, int count, int *total)
     return 1;
 }
 
-typedef struct {
-    int64_t offset;
-    int count;
-    int *total;
-    int ret;
-    bool done;
-} CoWriteZeroes;
-
-static void coroutine_fn co_write_zeroes_entry(void *opaque)
-{
-    CoWriteZeroes *data = opaque;
-
-    data->ret = bdrv_co_write_zeroes(bs, data->offset / BDRV_SECTOR_SIZE,
-                                     data->count / BDRV_SECTOR_SIZE);
-    data->done = true;
-    if (data->ret < 0) {
-        *data->total = data->ret;
-        return;
-    }
-
-    *data->total = data->count;
-}
-
-static int do_co_write_zeroes(int64_t offset, int count, int *total)
-{
-    Coroutine *co;
-    CoWriteZeroes data = {
-        .offset = offset,
-        .count  = count,
-        .total  = total,
-        .done   = false,
-    };
-
-    co = qemu_coroutine_create(co_write_zeroes_entry);
-    qemu_coroutine_enter(co, &data);
-    while (!data.done) {
-        qemu_aio_wait();
-    }
-    if (data.ret < 0) {
-        return data.ret;
-    } else {
-        return 1;
-    }
-}
-
 static int do_load_vmstate(char *buf, int64_t offset, int count, int *total)
 {
     *total = bdrv_load_vmstate(bs, (uint8_t *)buf, offset, count);
@@ -688,7 +643,6 @@ static void write_help(void)
 " -P, -- use different pattern to fill file\n"
 " -C, -- report statistics in a machine parsable format\n"
 " -q, -- quiet mode, do not show I/O statistics\n"
-" -z, -- write zeroes using bdrv_co_write_zeroes\n"
 "\n");
 }
 
@@ -717,7 +671,7 @@ static int write_f(int argc, char **argv)
     int total = 0;
     int pattern = 0xcd;
 
-    while ((c = getopt(argc, argv, "bCpP:qz")) != EOF) {
+    while ((c = getopt(argc, argv, "bCpP:q")) != EOF) {
         switch (c) {
         case 'b':
             bflag = 1;
@@ -796,8 +750,6 @@ static int write_f(int argc, char **argv)
         cnt = do_pwrite(buf, offset, count, &total);
     } else if (bflag) {
         cnt = do_save_vmstate(buf, offset, count, &total);
-    } else if (zflag) {
-        cnt = do_co_write_zeroes(offset, count, &total);
     } else {
         cnt = do_write(buf, offset, count, &total);
     }
diff --git a/tests/qemu-iotests/031 b/tests/qemu-iotests/031
index 9aee078..c88378e 100755
--- a/tests/qemu-iotests/031
+++ b/tests/qemu-iotests/031
@@ -1,6 +1,6 @@
 #!/bin/bash
 #
-# Test aligned and misaligned write zeroes operations.
+# Test aligned and misaligned discard operations.
 #
 # Copyright (C) 2012 Red Hat, Inc.
 #
@@ -50,7 +50,7 @@ echo
 echo "== preparing image =="
 $QEMU_IO -c "write -P 0xa 0x200 0x400" $TEST_IMG | _filter_qemu_io
 $QEMU_IO -c "write -P 0xa 0x20000 0x600" $TEST_IMG | _filter_qemu_io
-$QEMU_IO -c "write -z 0x400 0x20000" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "discard 0x400 0x20000" $TEST_IMG | _filter_qemu_io
 
 echo
 echo "== verifying patterns (1) =="
@@ -61,7 +61,7 @@ $QEMU_IO -c "read -P 0xa 0x20400 0x200" $TEST_IMG | _filter_qemu_io
 echo
 echo "== rewriting zeroes =="
 $QEMU_IO -c "write -P 0xb 0x10000 0x10000" $TEST_IMG | _filter_qemu_io
-$QEMU_IO -c "write -z 0x10000 0x10000" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "discard 0x10000 0x10000" $TEST_IMG | _filter_qemu_io
 
 echo
 echo "== verifying patterns (2) =="
diff --git a/tests/qemu-iotests/031.out b/tests/qemu-iotests/031.out
index 3c990dd..788ccfe 100644
--- a/tests/qemu-iotests/031.out
+++ b/tests/qemu-iotests/031.out
@@ -6,7 +6,7 @@ wrote 1024/1024 bytes at offset 512
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 1536/1536 bytes at offset 131072
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-wrote 131072/131072 bytes at offset 1024
+discard 131072/131072 bytes at offset 1024
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 
 == verifying patterns (1) ==
@@ -20,7 +20,7 @@ read 512/512 bytes at offset 132096
 == rewriting zeroes ==
 wrote 65536/65536 bytes at offset 65536
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-wrote 65536/65536 bytes at offset 65536
+discard 65536/65536 bytes at offset 65536
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 
 == verifying patterns (2) ==
-- 
1.7.7.6