blockdev: Add dynamic module loading for block drivers

Extend the current module interface to allow for block drivers to be
loaded dynamically on request. The only block drivers that can be
converted into modules are the drivers that don't perform any init
operation except for registering themselves.

In addition, only the protocol drivers are being modularized, as they
are the only ones which see significant performance benefits. The format
drivers do not generally link to external libraries, so modularizing
them is of no benefit from a performance perspective.

All the necessary module information is located in a new structure found
in module_block.h

This spoils the purpose of 5505e8b76f (block/dmg: make it modular).

Before this patch, if module build is enabled, block-dmg.so is linked to
libbz2, whereas the main binary is not. In downstream, theoretically, it
means only the qemu-block-extra package depends on libbz2, while the
main QEMU package needn't to. With this patch, we (temporarily) change
the case so that the main QEMU depends on libbz2 again.

Signed-off-by: Marc Marí <markmb@redhat.com>
Signed-off-by: Colin Lord <clord@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1471008424-16465-4-git-send-email-clord@redhat.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
[mreitz: Do a signed comparison against the length of
 block_driver_modules[], so it will not cause a compile error when
 empty]
Signed-off-by: Max Reitz <mreitz@redhat.com>

diff --git a/Makefile b/Makefile
index b7d1200c1661f248c9c3d6fb81d0c124b1152201..f10361675da412044eecf60f29867c4869318795 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -247,9 +247,6 @@ Makefile: $(version-obj-y) $(version-lobj-y)
 libqemustub.a: $(stub-obj-y)
 libqemuutil.a: $(util-obj-y)
 
-block-modules = $(foreach o,$(block-obj-m),"$(basename $(subst /,-,$o))",) NULL
-util/module.o-cflags = -D'CONFIG_BLOCK_MODULES=$(block-modules)'
-
 ######################################################################
 
 qemu-img.o: qemu-img-cmds.h

diff --git a/block.c b/block.c
index 66ed1c03219f9a2d9125c4630a35f10930a94dcc..afaff93423db26374a4bc728b3a5ae762159f98e 100644 (file)
--- a/block.c
+++ b/block.c
@@ -27,6 +27,7 @@
 #include "block/blockjob.h"
 #include "block/nbd.h"
 #include "qemu/error-report.h"
+#include "module_block.h"
 #include "qemu/module.h"
 #include "qapi/qmp/qerror.h"
 #include "qapi/qmp/qbool.h"
@@ -242,17 +243,40 @@ BlockDriverState *bdrv_new(void)
     return bs;
 }
 
-BlockDriver *bdrv_find_format(const char *format_name)
+static BlockDriver *bdrv_do_find_format(const char *format_name)
 {
     BlockDriver *drv1;
+
     QLIST_FOREACH(drv1, &bdrv_drivers, list) {
         if (!strcmp(drv1->format_name, format_name)) {
             return drv1;
         }
     }
+
     return NULL;
 }
 
+BlockDriver *bdrv_find_format(const char *format_name)
+{
+    BlockDriver *drv1;
+    int i;
+
+    drv1 = bdrv_do_find_format(format_name);
+    if (drv1) {
+        return drv1;
+    }
+
+    /* The driver isn't registered, maybe we need to load a module */
+    for (i = 0; i < (int)ARRAY_SIZE(block_driver_modules); ++i) {
+        if (!strcmp(block_driver_modules[i].format_name, format_name)) {
+            block_module_load_one(block_driver_modules[i].library_name);
+            break;
+        }
+    }
+
+    return bdrv_do_find_format(format_name);
+}
+
 static int bdrv_is_whitelisted(BlockDriver *drv, bool read_only)
 {
     static const char *whitelist_rw[] = {
@@ -461,6 +485,19 @@ static BlockDriver *find_hdev_driver(const char *filename)
     return drv;
 }
 
+static BlockDriver *bdrv_do_find_protocol(const char *protocol)
+{
+    BlockDriver *drv1;
+
+    QLIST_FOREACH(drv1, &bdrv_drivers, list) {
+        if (drv1->protocol_name && !strcmp(drv1->protocol_name, protocol)) {
+            return drv1;
+        }
+    }
+
+    return NULL;
+}
+
 BlockDriver *bdrv_find_protocol(const char *filename,
                                 bool allow_protocol_prefix,
                                 Error **errp)
@@ -469,6 +506,7 @@ BlockDriver *bdrv_find_protocol(const char *filename,
     char protocol[128];
     int len;
     const char *p;
+    int i;
 
     /* TODO Drivers without bdrv_file_open must be specified explicitly */
 
@@ -495,15 +533,25 @@ BlockDriver *bdrv_find_protocol(const char *filename,
         len = sizeof(protocol) - 1;
     memcpy(protocol, filename, len);
     protocol[len] = '\0';
-    QLIST_FOREACH(drv1, &bdrv_drivers, list) {
-        if (drv1->protocol_name &&
-            !strcmp(drv1->protocol_name, protocol)) {
-            return drv1;
+
+    drv1 = bdrv_do_find_protocol(protocol);
+    if (drv1) {
+        return drv1;
+    }
+
+    for (i = 0; i < (int)ARRAY_SIZE(block_driver_modules); ++i) {
+        if (block_driver_modules[i].protocol_name &&
+            !strcmp(block_driver_modules[i].protocol_name, protocol)) {
+            block_module_load_one(block_driver_modules[i].library_name);
+            break;
         }
     }
 
-    error_setg(errp, "Unknown protocol '%s'", protocol);
-    return NULL;
+    drv1 = bdrv_do_find_protocol(protocol);
+    if (!drv1) {
+        error_setg(errp, "Unknown protocol '%s'", protocol);
+    }
+    return drv1;
 }
 
 /*

diff --git a/block/Makefile.objs b/block/Makefile.objs
index 55da6266fe4b1e00076a9cabd5bfa0a8b20c0926..3da471e388682dc2c9e73e9c0af2bb39ea6920de 100644 (file)
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -1,4 +1,4 @@
-block-obj-y += raw_bsd.o qcow.o vdi.o vmdk.o cloop.o bochs.o vpc.o vvfat.o
+block-obj-y += raw_bsd.o qcow.o vdi.o vmdk.o cloop.o bochs.o vpc.o vvfat.o dmg.o
 block-obj-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o qcow2-cache.o
 block-obj-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
 block-obj-y += qed-check.o
@@ -40,7 +40,6 @@ gluster.o-libs     := $(GLUSTERFS_LIBS)
 ssh.o-cflags       := $(LIBSSH2_CFLAGS)
 ssh.o-libs         := $(LIBSSH2_LIBS)
 archipelago.o-libs := $(ARCHIPELAGO_LIBS)
-block-obj-m        += dmg.o
 dmg.o-libs         := $(BZIP2_LIBS)
 qcow.o-libs        := -lz
 linux-aio.o-libs   := -laio

diff --git a/include/qemu/module.h b/include/qemu/module.h
index 2370708445af94a4f4638e001409d68b46f4662e..dc2c9d4c4eee7ac6bfadd8853099397045cd0f8f 100644 (file)
--- a/include/qemu/module.h
+++ b/include/qemu/module.h
@@ -52,9 +52,12 @@ typedef enum {
 #define qapi_init(function) module_init(function, MODULE_INIT_QAPI)
 #define type_init(function) module_init(function, MODULE_INIT_QOM)
 
+#define block_module_load_one(lib) module_load_one("block-", lib)
+
 void register_module_init(void (*fn)(void), module_init_type type);
 void register_dso_module_init(void (*fn)(void), module_init_type type);
 
 void module_call_init(module_init_type type);
+void module_load_one(const char *prefix, const char *lib_name);
 
 #endif

diff --git a/util/module.c b/util/module.c
index 86e3f7aba0067009eee18550dc40b40f486a53dd..a5f7fbd94133acf9488fa17e6b6c9b2faea99743 100644 (file)
--- a/util/module.c
+++ b/util/module.c
@@ -87,14 +87,11 @@ void register_dso_module_init(void (*fn)(void), module_init_type type)
     QTAILQ_INSERT_TAIL(&dso_init_list, e, node);
 }
 
-static void module_load(module_init_type type);
-
 void module_call_init(module_init_type type)
 {
     ModuleTypeList *l;
     ModuleEntry *e;
 
-    module_load(type);
     l = find_type(type);
 
     QTAILQ_FOREACH(e, l, node) {
@@ -145,6 +142,7 @@ static int module_load_file(const char *fname)
         ret = -EINVAL;
     } else {
         QTAILQ_FOREACH(e, &dso_init_list, node) {
+            e->init();
             register_module_init(e->init, e->type);
         }
         ret = 0;
@@ -159,14 +157,10 @@ out:
 }
 #endif
 
-static void module_load(module_init_type type)
+void module_load_one(const char *prefix, const char *lib_name)
 {
 #ifdef CONFIG_MODULES
     char *fname = NULL;
-    const char **mp;
-    static const char *block_modules[] = {
-        CONFIG_BLOCK_MODULES
-    };
     char *exec_dir;
     char *dirs[3];
     int i = 0;
@@ -177,15 +171,6 @@ static void module_load(module_init_type type)
         return;
     }
 
-    switch (type) {
-    case MODULE_INIT_BLOCK:
-        mp = block_modules;
-        break;
-    default:
-        /* no other types have dynamic modules for now*/
-        return;
-    }
-
     exec_dir = qemu_get_exec_dir();
     dirs[i++] = g_strdup_printf("%s", CONFIG_QEMU_MODDIR);
     dirs[i++] = g_strdup_printf("%s/..", exec_dir ? : "");
@@ -194,16 +179,15 @@ static void module_load(module_init_type type)
     g_free(exec_dir);
     exec_dir = NULL;
 
-    for ( ; *mp; mp++) {
-        for (i = 0; i < ARRAY_SIZE(dirs); i++) {
-            fname = g_strdup_printf("%s/%s%s", dirs[i], *mp, HOST_DSOSUF);
-            ret = module_load_file(fname);
-            g_free(fname);
-            fname = NULL;
-            /* Try loading until loaded a module file */
-            if (!ret) {
-                break;
-            }
+    for (i = 0; i < ARRAY_SIZE(dirs); i++) {
+        fname = g_strdup_printf("%s/%s%s%s",
+                dirs[i], prefix, lib_name, HOST_DSOSUF);
+        ret = module_load_file(fname);
+        g_free(fname);
+        fname = NULL;
+        /* Try loading until loaded a module file */
+        if (!ret) {
+            break;
         }
     }