block: Remove BDRV_O_CACHE_WB

The previous patches have successively made blk->enable_write_cache the true source for the information whether a writethrough mode must be implemented. The corresponding BDRV_O_CACHE_WB is only useless baggage we're carrying around, so now's the time to remove it. At the same time, we remove the 'cache.writeback' option parsing on the BDS level as the only effect was setting the BDRV_O_CACHE_WB flag. This change requires test cases that explicitly enabled the option to drop it. Other than that and the change of the error message when writethrough is enabled on the BDS level (from "Can't set writethrough mode" to "doesn't support the option"), there should be no change in behaviour. Signed-off-by: Kevin Wolf <[email protected]> Reviewed-by: Max Reitz <[email protected]>
shreyasbp · Mar 30, 2016 · 61de4c6 · 61de4c6
1 parent 53e8ae0
commit 61de4c6
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Showing 11 changed files with 34 additions and 109 deletions.
diff --git a/block.c b/block.c
@@ -680,7 +680,6 @@ static void bdrv_temp_snapshot_options(int *child_flags, QDict *child_options,
     *child_flags = (parent_flags & ~BDRV_O_SNAPSHOT) | BDRV_O_TEMPORARY;
 
     /* For temporary files, unconditional cache=unsafe is fine */
-    qdict_set_default_str(child_options, BDRV_OPT_CACHE_WB, "on");
     qdict_set_default_str(child_options, BDRV_OPT_CACHE_DIRECT, "off");
     qdict_set_default_str(child_options, BDRV_OPT_CACHE_NO_FLUSH, "on");
 }
@@ -705,7 +704,6 @@ static void bdrv_inherited_options(int *child_flags, QDict *child_options,
     /* Our block drivers take care to send flushes and respect unmap policy,
      * so we can default to enable both on lower layers regardless of the
      * corresponding parent options. */
-    qdict_set_default_str(child_options, BDRV_OPT_CACHE_WB, "on");
     flags |= BDRV_O_UNMAP;
 
     /* Clear flags that only apply to the top layer */
@@ -748,7 +746,6 @@ static void bdrv_backing_options(int *child_flags, QDict *child_options,
 
     /* The cache mode is inherited unmodified for backing files; except WCE,
      * which is only applied on the top level (BlockBackend) */
-    qdict_set_default_str(child_options, BDRV_OPT_CACHE_WB, "on");
     qdict_copy_default(child_options, parent_options, BDRV_OPT_CACHE_DIRECT);
     qdict_copy_default(child_options, parent_options, BDRV_OPT_CACHE_NO_FLUSH);
 
@@ -767,7 +764,7 @@ static const BdrvChildRole child_backing = {
 
 static int bdrv_open_flags(BlockDriverState *bs, int flags)
 {
-    int open_flags = flags | BDRV_O_CACHE_WB;
+    int open_flags = flags;
 
     /*
      * Clear flags that are internal to the block layer before opening the
@@ -789,11 +786,6 @@ static void update_flags_from_options(int *flags, QemuOpts *opts)
 {
     *flags &= ~BDRV_O_CACHE_MASK;
 
-    assert(qemu_opt_find(opts, BDRV_OPT_CACHE_WB));
-    if (qemu_opt_get_bool(opts, BDRV_OPT_CACHE_WB, false)) {
-        *flags |= BDRV_O_CACHE_WB;
-    }
-
     assert(qemu_opt_find(opts, BDRV_OPT_CACHE_NO_FLUSH));
     if (qemu_opt_get_bool(opts, BDRV_OPT_CACHE_NO_FLUSH, false)) {
         *flags |= BDRV_O_NO_FLUSH;
@@ -807,10 +799,6 @@ static void update_flags_from_options(int *flags, QemuOpts *opts)
 
 static void update_options_from_flags(QDict *options, int flags)
 {
-    if (!qdict_haskey(options, BDRV_OPT_CACHE_WB)) {
-        qdict_put(options, BDRV_OPT_CACHE_WB,
-                  qbool_from_bool(flags & BDRV_O_CACHE_WB));
-    }
     if (!qdict_haskey(options, BDRV_OPT_CACHE_DIRECT)) {
         qdict_put(options, BDRV_OPT_CACHE_DIRECT,
                   qbool_from_bool(flags & BDRV_O_NOCACHE));
@@ -872,11 +860,6 @@ static QemuOptsList bdrv_runtime_opts = {
             .type = QEMU_OPT_STRING,
             .help = "Block driver to use for the node",
         },
-        {
-            .name = BDRV_OPT_CACHE_WB,
-            .type = QEMU_OPT_BOOL,
-            .help = "Enable writeback mode",
-        },
         {
             .name = BDRV_OPT_CACHE_DIRECT,
             .type = QEMU_OPT_BOOL,
@@ -984,14 +967,6 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
     /* Apply cache mode options */
     update_flags_from_options(&bs->open_flags, opts);
 
-    if (!bs->blk && (bs->open_flags & BDRV_O_CACHE_WB) == 0) {
-        error_setg(errp, "Can't set writethrough mode except for the root");
-        ret = -EINVAL;
-        goto free_and_fail;
-    }
-
-    bdrv_set_enable_write_cache(bs, bs->open_flags & BDRV_O_CACHE_WB);
-
     /* Open the image, either directly or using a protocol */
     open_flags = bdrv_open_flags(bs, bs->open_flags);
     if (drv->bdrv_file_open) {
@@ -2013,16 +1988,6 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
 
     update_flags_from_options(&reopen_state->flags, opts);
 
-    /* WCE is a BlockBackend level option, can't change it */
-    bool old_wce = bdrv_enable_write_cache(reopen_state->bs);
-    bool new_wce = (reopen_state->flags & BDRV_O_CACHE_WB);
-
-    if (old_wce != new_wce) {
-        error_setg(errp, "Cannot change cache.writeback");
-        ret = -EINVAL;
-        goto error;
-    }
-
     /* node-name and driver must be unchanged. Put them back into the QDict, so
      * that they are checked at the end of this function. */
     value = qemu_opt_get(opts, "node-name");
@@ -2124,8 +2089,6 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
     reopen_state->bs->open_flags         = reopen_state->flags;
     reopen_state->bs->read_only = !(reopen_state->flags & BDRV_O_RDWR);
 
-    bdrv_set_enable_write_cache(reopen_state->bs,
-                                !!(reopen_state->flags & BDRV_O_CACHE_WB));
     bdrv_refresh_limits(reopen_state->bs, NULL);
 }
 
@@ -2746,13 +2709,6 @@ void bdrv_set_enable_write_cache(BlockDriverState *bs, bool wce)
     if (bs->blk) {
         blk_set_enable_write_cache(bs->blk, wce);
     }
-
-    /* so a reopen() will preserve wce */
-    if (wce) {
-        bs->open_flags |= BDRV_O_CACHE_WB;
-    } else {
-        bs->open_flags &= ~BDRV_O_CACHE_WB;
-    }
 }
 
 int bdrv_is_encrypted(BlockDriverState *bs)
@@ -3605,7 +3561,7 @@ void bdrv_img_create(const char *filename, const char *fmt,
             }
 
             /* backing files always opened read-only */
-            back_flags = flags | BDRV_O_CACHE_WB;
+            back_flags = flags;
             back_flags &= ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
 
             if (backing_fmt) {

diff --git a/block/block-backend.c b/block/block-backend.c
@@ -150,8 +150,6 @@ BlockBackend *blk_new_open(const char *filename, const char *reference,
     BlockBackend *blk;
     int ret;
 
-    assert((flags & BDRV_O_CACHE_WB) == 0);
-
     blk = blk_new_with_bs(errp);
     if (!blk) {
         QDECREF(options);
@@ -1224,15 +1222,6 @@ int blk_enable_write_cache(BlockBackend *blk)
 void blk_set_enable_write_cache(BlockBackend *blk, bool wce)
 {
     blk->enable_write_cache = wce;
-
-    /* TODO Remove this when BDRV_O_CACHE_WB isn't used any more */
-    if (blk->root) {
-        if (wce) {
-            blk->root->bs->open_flags |= BDRV_O_CACHE_WB;
-        } else {
-            blk->root->bs->open_flags &= ~BDRV_O_CACHE_WB;
-        }
-    }
 }
 
 void blk_invalidate_cache(BlockBackend *blk, Error **errp)

diff --git a/block/vvfat.c b/block/vvfat.c
@@ -2957,8 +2957,7 @@ static int enable_write_target(BDRVVVFATState *s, Error **errp)
     options = qdict_new();
     qdict_put(options, "driver", qstring_from_str("qcow"));
     ret = bdrv_open(&s->qcow, s->qcow_filename, NULL, options,
-                    BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH,
-                    errp);
+                    BDRV_O_RDWR | BDRV_O_NO_FLUSH, errp);
     if (ret < 0) {
         goto err;
     }

diff --git a/blockdev.c b/blockdev.c
@@ -595,7 +595,6 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
         /* bdrv_open() defaults to the values in bdrv_flags (for compatibility
          * with other callers) rather than what we want as the real defaults.
          * Apply the defaults here instead. */
-        qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_WB, writethrough ? "off" : "on");
         qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_DIRECT, "off");
         qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_NO_FLUSH, "off");
         assert((bdrv_flags & BDRV_O_CACHE_MASK) == 0);
@@ -691,7 +690,6 @@ static BlockDriverState *bds_tree_init(QDict *bs_opts, Error **errp)
     /* bdrv_open() defaults to the values in bdrv_flags (for compatibility
      * with other callers) rather than what we want as the real defaults.
      * Apply the defaults here instead. */
-    qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_WB, "on");
     qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_DIRECT, "off");
     qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_NO_FLUSH, "off");
 
@@ -1779,12 +1777,6 @@ static void external_snapshot_prepare(BlkActionState *common,
         flags |= BDRV_O_NO_BACKING;
     }
 
-    /* There is no BB attached during bdrv_open(), so we can't set a
-     * writethrough mode. bdrv_append() will swap the WCE setting so that the
-     * backing file becomes unconditionally writeback (which is what backing
-     * files should always be) and the new overlay gets the original setting. */
-    flags |= BDRV_O_CACHE_WB;
-
     assert(state->new_bs == NULL);
     ret = bdrv_open(&state->new_bs, new_image_file, snapshot_ref, options,
                     flags, errp);
@@ -2529,7 +2521,6 @@ void qmp_blockdev_change_medium(const char *device, const char *filename,
     BlockBackend *blk;
     BlockDriverState *medium_bs = NULL;
     int bdrv_flags, ret;
-    bool writethrough;
     QDict *options = NULL;
     Error *err = NULL;
 
@@ -2548,12 +2539,6 @@ void qmp_blockdev_change_medium(const char *device, const char *filename,
     bdrv_flags &= ~(BDRV_O_TEMPORARY | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING |
         BDRV_O_PROTOCOL);
 
-    /* Must open the image in writeback mode as long as no BlockBackend is
-     * attached. The right mode can be set as the final step after changing the
-     * medium. */
-    writethrough = !(bdrv_flags & BDRV_O_CACHE_WB);
-    bdrv_flags |= BDRV_O_CACHE_WB;
-
     if (!has_read_only) {
         read_only = BLOCKDEV_CHANGE_READ_ONLY_MODE_RETAIN;
     }
@@ -2611,8 +2596,6 @@ void qmp_blockdev_change_medium(const char *device, const char *filename,
         goto fail;
     }
 
-    bdrv_set_enable_write_cache(medium_bs, !writethrough);
-
     qmp_blockdev_close_tray(device, errp);
 
 fail:
@@ -3238,7 +3221,7 @@ static void do_drive_backup(const char *device, const char *target,
         goto out;
     }
 
-    flags = bs->open_flags | BDRV_O_CACHE_WB | BDRV_O_RDWR;
+    flags = bs->open_flags | BDRV_O_RDWR;
 
     /* See if we have a backing HD we can use to create our new image
      * on top of. */
@@ -3533,7 +3516,7 @@ void qmp_drive_mirror(const char *device, const char *target,
         format = mode == NEW_IMAGE_MODE_EXISTING ? NULL : bs->drv->format_name;
     }
 
-    flags = bs->open_flags | BDRV_O_CACHE_WB | BDRV_O_RDWR;
+    flags = bs->open_flags | BDRV_O_RDWR;
     source = backing_bs(bs);
     if (!source && sync == MIRROR_SYNC_MODE_TOP) {
         sync = MIRROR_SYNC_MODE_FULL;

diff --git a/include/block/block.h b/include/block/block.h
@@ -82,7 +82,6 @@ typedef struct HDGeometry {
 #define BDRV_O_SNAPSHOT    0x0008 /* open the file read only and save writes in a snapshot */
 #define BDRV_O_TEMPORARY   0x0010 /* delete the file after use */
 #define BDRV_O_NOCACHE     0x0020 /* do not use the host page cache */
-#define BDRV_O_CACHE_WB    0x0040 /* use write-back caching */
 #define BDRV_O_NATIVE_AIO  0x0080 /* use native AIO instead of the thread pool */
 #define BDRV_O_NO_BACKING  0x0100 /* don't open the backing file */
 #define BDRV_O_NO_FLUSH    0x0200 /* disable flushing on this disk */
@@ -96,7 +95,7 @@ typedef struct HDGeometry {
                                       ignoring the format layer */
 #define BDRV_O_NO_IO       0x10000 /* don't initialize for I/O */
 
-#define BDRV_O_CACHE_MASK  (BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH)
+#define BDRV_O_CACHE_MASK  (BDRV_O_NOCACHE | BDRV_O_NO_FLUSH)
 
 
 /* Option names of options parsed by the block layer */

diff --git a/qemu-img.c b/qemu-img.c
@@ -463,7 +463,7 @@ static int img_create(int argc, char **argv)
     }
 
     bdrv_img_create(filename, fmt, base_filename, base_fmt,
-                    options, img_size, BDRV_O_CACHE_WB, &local_err, quiet);
+                    options, img_size, 0, &local_err, quiet);
     if (local_err) {
         error_reportf_err(local_err, "%s: ", filename);
         goto fail;

diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
@@ -2151,7 +2151,6 @@ static int reopen_f(BlockBackend *blk, int argc, char **argv)
     opts = qopts ? qemu_opts_to_qdict(qopts, NULL) : NULL;
     qemu_opts_reset(&reopen_opts);
 
-    flags |= blk_enable_write_cache(blk) ? BDRV_O_CACHE_WB : 0;
     brq = bdrv_reopen_queue(NULL, bs, opts, flags);
     bdrv_reopen_multiple(brq, &local_err);
     if (local_err) {

diff --git a/tests/qemu-iotests/051 b/tests/qemu-iotests/051
@@ -218,7 +218,7 @@ run_qemu -drive driver=null-co,cache=invalid_value
 
 for cache in writeback writethrough unsafe invalid_value; do
     echo -e "info block\ninfo block file\ninfo block backing\ninfo block backing-file" | \
-    run_qemu -drive file="$TEST_IMG",cache=$cache,backing.file.filename="$TEST_IMG.base",backing.cache.no-flush=on,backing.cache.writeback=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=$device_id -nodefaults
+    run_qemu -drive file="$TEST_IMG",cache=$cache,backing.file.filename="$TEST_IMG.base",backing.cache.no-flush=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=$device_id -nodefaults
 done
 
 echo

diff --git a/tests/qemu-iotests/051.pc.out b/tests/qemu-iotests/051.pc.out
@@ -239,7 +239,7 @@ QEMU X.Y.Z monitor - type 'help' for more information
 Testing: -drive driver=null-co,cache=invalid_value
 QEMU_PROG: -drive driver=null-co,cache=invalid_value: invalid cache option
 
-Testing: -drive file=TEST_DIR/t.qcow2,cache=writeback,backing.file.filename=TEST_DIR/t.qcow2.base,backing.cache.no-flush=on,backing.cache.writeback=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=drive0 -nodefaults
+Testing: -drive file=TEST_DIR/t.qcow2,cache=writeback,backing.file.filename=TEST_DIR/t.qcow2.base,backing.cache.no-flush=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=drive0 -nodefaults
 QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) i[K[Din[K[D[Dinf[K[D[D[Dinfo[K[D[D[D[Dinfo [K[D[D[D[D[Dinfo b[K[D[D[D[D[D[Dinfo bl[K[D[D[D[D[D[D[Dinfo blo[K[D[D[D[D[D[D[D[Dinfo bloc[K[D[D[D[D[D[D[D[D[Dinfo block[K
 drive0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
@@ -259,7 +259,7 @@ backing-file: TEST_DIR/t.qcow2.base (file, read-only)
     Cache mode:       writeback, ignore flushes
 (qemu) q[K[Dqu[K[D[Dqui[K[D[D[Dquit[K
 
-Testing: -drive file=TEST_DIR/t.qcow2,cache=writethrough,backing.file.filename=TEST_DIR/t.qcow2.base,backing.cache.no-flush=on,backing.cache.writeback=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=drive0 -nodefaults
+Testing: -drive file=TEST_DIR/t.qcow2,cache=writethrough,backing.file.filename=TEST_DIR/t.qcow2.base,backing.cache.no-flush=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=drive0 -nodefaults
 QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) i[K[Din[K[D[Dinf[K[D[D[Dinfo[K[D[D[D[Dinfo [K[D[D[D[D[Dinfo b[K[D[D[D[D[D[Dinfo bl[K[D[D[D[D[D[D[Dinfo blo[K[D[D[D[D[D[D[D[Dinfo bloc[K[D[D[D[D[D[D[D[D[Dinfo block[K
 drive0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
@@ -279,7 +279,7 @@ backing-file: TEST_DIR/t.qcow2.base (file, read-only)
     Cache mode:       writeback, ignore flushes
 (qemu) q[K[Dqu[K[D[Dqui[K[D[D[Dquit[K
 
-Testing: -drive file=TEST_DIR/t.qcow2,cache=unsafe,backing.file.filename=TEST_DIR/t.qcow2.base,backing.cache.no-flush=on,backing.cache.writeback=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=drive0 -nodefaults
+Testing: -drive file=TEST_DIR/t.qcow2,cache=unsafe,backing.file.filename=TEST_DIR/t.qcow2.base,backing.cache.no-flush=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=drive0 -nodefaults
 QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) i[K[Din[K[D[Dinf[K[D[D[Dinfo[K[D[D[D[Dinfo [K[D[D[D[D[Dinfo b[K[D[D[D[D[D[Dinfo bl[K[D[D[D[D[D[D[Dinfo blo[K[D[D[D[D[D[D[D[Dinfo bloc[K[D[D[D[D[D[D[D[D[Dinfo block[K
 drive0 (NODE_NAME): TEST_DIR/t.qcow2 (qcow2)
@@ -299,8 +299,8 @@ backing-file: TEST_DIR/t.qcow2.base (file, read-only)
     Cache mode:       writeback, ignore flushes
 (qemu) q[K[Dqu[K[D[Dqui[K[D[D[Dquit[K
 
-Testing: -drive file=TEST_DIR/t.qcow2,cache=invalid_value,backing.file.filename=TEST_DIR/t.qcow2.base,backing.cache.no-flush=on,backing.cache.writeback=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=drive0 -nodefaults
-QEMU_PROG: -drive file=TEST_DIR/t.qcow2,cache=invalid_value,backing.file.filename=TEST_DIR/t.qcow2.base,backing.cache.no-flush=on,backing.cache.writeback=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=drive0: invalid cache option
+Testing: -drive file=TEST_DIR/t.qcow2,cache=invalid_value,backing.file.filename=TEST_DIR/t.qcow2.base,backing.cache.no-flush=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=drive0 -nodefaults
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,cache=invalid_value,backing.file.filename=TEST_DIR/t.qcow2.base,backing.cache.no-flush=on,backing.node-name=backing,backing.file.node-name=backing-file,file.node-name=file,if=none,id=drive0: invalid cache option
 
 
 === Specifying the protocol layer ===

diff --git a/tests/qemu-iotests/142 b/tests/qemu-iotests/142
@@ -110,11 +110,11 @@ function check_cache_all()
     echo -e "\n\ncache.writeback=off on none0"
     echo "$hmp_cmds" | run_qemu -drive "$files","$ids",cache.writeback=off | grep -e "Cache" -e "[Cc]annot\|[Cc]ould not\|[Cc]an't"
     echo -e "\ncache.writeback=off on file"
-    echo "$hmp_cmds" | run_qemu -drive "$files","$ids",file.cache.writeback=off | grep -e "Cache" -e "[Cc]annot\|[Cc]ould not\|[Cc]an't"
+    echo "$hmp_cmds" | run_qemu -drive "$files","$ids",file.cache.writeback=off | grep -e "doesn't" -e "does not"
     echo -e "\ncache.writeback=off on backing"
-    echo "$hmp_cmds" | run_qemu -drive "$files","$ids",backing.cache.writeback=off | grep -e "Cache" -e "[Cc]annot\|[Cc]ould not\|[Cc]an't"
+    echo "$hmp_cmds" | run_qemu -drive "$files","$ids",backing.cache.writeback=off | grep -e "doesn't" -e "does not"
     echo -e "\ncache.writeback=off on backing-file"
-    echo "$hmp_cmds" | run_qemu -drive "$files","$ids",backing.file.cache.writeback=off | grep -e "Cache" -e "[Cc]annot\|[Cc]ould not\|[Cc]an't"
+    echo "$hmp_cmds" | run_qemu -drive "$files","$ids",backing.file.cache.writeback=off | grep -e "doesn't" -e "does not"
 
     # cache.no-flush is supposed to be inherited by both bs->file and bs->backing