[Qemu-devel] [PATCH v2 0/6] nbd: Use BlockBackend

[Qemu-devel] [PATCH v2 0/6] nbd: Use BlockBackend

[Max Reitz]

>From the block layer's perspective, the nbd server is pretty similar to
a guest device. Therefore, it should use BlockBackend to access block
devices, just like any other guest device does.

This series consequently makes the nbd server use BlockBackend for
referencing block devices.


v2:
- Added patch 6, which converts qemu-nbd to BlockBackend as far as
  reasonable [Paolo]


git-backport-diff against v1:

Key:
[----] : patches are identical
[####] : number of functional differences between upstream/downstream patch
[down] : patch is downstream-only
The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively

001/6:[----] [--] 'block: Lift more functions into BlockBackend'
002/6:[----] [--] 'block: Add AioContextNotifier functions to BB'
003/6:[----] [--] 'block: Add blk_add_close_notifier() for BB'
004/6:[----] [--] 'nbd: Change external interface to BlockBackend'
005/6:[----] [--] 'nbd: Use BlockBackend internally'
006/6:[down] 'qemu-nbd: Use BlockBackend where reasonable'


Max Reitz (6):
  block: Lift more functions into BlockBackend
  block: Add AioContextNotifier functions to BB
  block: Add blk_add_close_notifier() for BB
  nbd: Change external interface to BlockBackend
  nbd: Use BlockBackend internally
  qemu-nbd: Use BlockBackend where reasonable

 block/block-backend.c          | 38 +++++++++++++++++++++++++
 blockdev-nbd.c                 | 15 +++++-----
 include/block/nbd.h            |  7 ++---
 include/sysemu/block-backend.h | 12 ++++++++
 nbd.c                          | 63 +++++++++++++++++++++---------------------
 qemu-nbd.c                     | 12 ++++----
 6 files changed, 99 insertions(+), 48 deletions(-)

-- 
1.9.3

[Qemu-devel] [PATCH v2 1/6] block: Lift more functions into BlockBackend

[Max Reitz]

There are already some blk_aio_* functions, so we might as well have
blk_co_* functions (as far as we need them). This patch adds
blk_co_flush(), blk_co_discard(), and also blk_invalidate_cache() (which
is not a blk_co_* function but is needed nonetheless).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/block-backend.c          | 15 +++++++++++++++
 include/sysemu/block-backend.h |  3 +++
 2 files changed, 18 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index d0692b1..89f69b7 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -497,6 +497,16 @@ BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
     return bdrv_aio_ioctl(blk->bs, req, buf, cb, opaque);
 }
 
+int blk_co_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors)
+{
+    return bdrv_co_discard(blk->bs, sector_num, nb_sectors);
+}
+
+int blk_co_flush(BlockBackend *blk)
+{
+    return bdrv_co_flush(blk->bs);
+}
+
 int blk_flush(BlockBackend *blk)
 {
     return bdrv_flush(blk->bs);
@@ -549,6 +559,11 @@ void blk_set_enable_write_cache(BlockBackend *blk, bool wce)
     bdrv_set_enable_write_cache(blk->bs, wce);
 }
 
+void blk_invalidate_cache(BlockBackend *blk, Error **errp)
+{
+    bdrv_invalidate_cache(blk->bs, errp);
+}
+
 int blk_is_inserted(BlockBackend *blk)
 {
     return bdrv_is_inserted(blk->bs);
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 52d13c1..0c46b82 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -108,6 +108,8 @@ int blk_aio_multiwrite(BlockBackend *blk, BlockRequest *reqs, int num_reqs);
 int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf);
 BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
                           BlockCompletionFunc *cb, void *opaque);
+int blk_co_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors);
+int blk_co_flush(BlockBackend *blk);
 int blk_flush(BlockBackend *blk);
 int blk_flush_all(void);
 void blk_drain_all(void);
@@ -120,6 +122,7 @@ int blk_is_read_only(BlockBackend *blk);
 int blk_is_sg(BlockBackend *blk);
 int blk_enable_write_cache(BlockBackend *blk);
 void blk_set_enable_write_cache(BlockBackend *blk, bool wce);
+void blk_invalidate_cache(BlockBackend *blk, Error **errp);
 int blk_is_inserted(BlockBackend *blk);
 void blk_lock_medium(BlockBackend *blk, bool locked);
 void blk_eject(BlockBackend *blk, bool eject_flag);
-- 
1.9.3

[Qemu-devel] [PATCH v2 2/6] block: Add AioContextNotifier functions to BB

[Max Reitz]

Because all BlockDriverStates behind a single BlockBackend reside in a
single AioContext, it is fine to just pass these functions
(blk_add_aio_context_notifier() and blk_remove_aio_context_notifier())
through to the root BlockDriverState.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/block-backend.c          | 18 ++++++++++++++++++
 include/sysemu/block-backend.h |  8 ++++++++
 2 files changed, 26 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index 89f69b7..7a7f690 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -624,6 +624,24 @@ void blk_set_aio_context(BlockBackend *blk, AioContext *new_context)
     bdrv_set_aio_context(blk->bs, new_context);
 }
 
+void blk_add_aio_context_notifier(BlockBackend *blk,
+        void (*attached_aio_context)(AioContext *new_context, void *opaque),
+        void (*detach_aio_context)(void *opaque), void *opaque)
+{
+    bdrv_add_aio_context_notifier(blk->bs, attached_aio_context,
+                                  detach_aio_context, opaque);
+}
+
+void blk_remove_aio_context_notifier(BlockBackend *blk,
+                                     void (*attached_aio_context)(AioContext *,
+                                                                  void *),
+                                     void (*detach_aio_context)(void *),
+                                     void *opaque)
+{
+    bdrv_remove_aio_context_notifier(blk->bs, attached_aio_context,
+                                     detach_aio_context, opaque);
+}
+
 void blk_io_plug(BlockBackend *blk)
 {
     bdrv_io_plug(blk->bs);
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 0c46b82..d9c1337 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -135,6 +135,14 @@ void blk_op_block_all(BlockBackend *blk, Error *reason);
 void blk_op_unblock_all(BlockBackend *blk, Error *reason);
 AioContext *blk_get_aio_context(BlockBackend *blk);
 void blk_set_aio_context(BlockBackend *blk, AioContext *new_context);
+void blk_add_aio_context_notifier(BlockBackend *blk,
+        void (*attached_aio_context)(AioContext *new_context, void *opaque),
+        void (*detach_aio_context)(void *opaque), void *opaque);
+void blk_remove_aio_context_notifier(BlockBackend *blk,
+                                     void (*attached_aio_context)(AioContext *,
+                                                                  void *),
+                                     void (*detach_aio_context)(void *),
+                                     void *opaque);
 void blk_io_plug(BlockBackend *blk);
 void blk_io_unplug(BlockBackend *blk);
 BlockAcctStats *blk_get_stats(BlockBackend *blk);
-- 
1.9.3

[Qemu-devel] [PATCH v2 3/6] block: Add blk_add_close_notifier() for BB

[Max Reitz]

Adding something like a "delete notifier" to a BlockBackend would not
make much sense, because whoever is interested in registering there will
probably hold a reference to that BlockBackend; therefore, the notifier
will never be called (or only when the notifiee already relinquished its
reference and thus most probably is no longer interested in that
notification).

Therefore, this patch just passes through the close notifier interface
of the root BDS. This will be called when the device is ejected, for
instance, and therefore does make sense.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/block-backend.c          | 5 +++++
 include/sysemu/block-backend.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index 7a7f690..ef16d73 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -642,6 +642,11 @@ void blk_remove_aio_context_notifier(BlockBackend *blk,
                                      detach_aio_context, opaque);
 }
 
+void blk_add_close_notifier(BlockBackend *blk, Notifier *notify)
+{
+    bdrv_add_close_notifier(blk->bs, notify);
+}
+
 void blk_io_plug(BlockBackend *blk)
 {
     bdrv_io_plug(blk->bs);
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index d9c1337..8871a02 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -143,6 +143,7 @@ void blk_remove_aio_context_notifier(BlockBackend *blk,
                                                                   void *),
                                      void (*detach_aio_context)(void *),
                                      void *opaque);
+void blk_add_close_notifier(BlockBackend *blk, Notifier *notify);
 void blk_io_plug(BlockBackend *blk);
 void blk_io_unplug(BlockBackend *blk);
 BlockAcctStats *blk_get_stats(BlockBackend *blk);
-- 
1.9.3

[Qemu-devel] [PATCH v2 4/6] nbd: Change external interface to BlockBackend

[Max Reitz]

Substitute BlockDriverState by BlockBackend in every globally visible
function provided by nbd.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 blockdev-nbd.c      | 15 ++++++++-------
 include/block/nbd.h |  7 +++----
 nbd.c               | 11 ++++++-----
 qemu-nbd.c          |  2 +-
 4 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index 06f901e..22e95d1 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -10,6 +10,7 @@
  */
 
 #include "sysemu/blockdev.h"
+#include "sysemu/block-backend.h"
 #include "hw/block/block.h"
 #include "monitor/monitor.h"
 #include "qapi/qmp/qerror.h"
@@ -73,7 +74,7 @@ static void nbd_close_notifier(Notifier *n, void *data)
 void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
                         Error **errp)
 {
-    BlockDriverState *bs;
+    BlockBackend *blk;
     NBDExport *exp;
     NBDCloseNotifier *n;
 
@@ -87,12 +88,12 @@ void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
         return;
     }
 
-    bs = bdrv_find(device);
-    if (!bs) {
+    blk = blk_by_name(device);
+    if (!blk) {
         error_set(errp, QERR_DEVICE_NOT_FOUND, device);
         return;
     }
-    if (!bdrv_is_inserted(bs)) {
+    if (!blk_is_inserted(blk)) {
         error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
         return;
     }
@@ -100,18 +101,18 @@ void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
     if (!has_writable) {
         writable = false;
     }
-    if (bdrv_is_read_only(bs)) {
+    if (blk_is_read_only(blk)) {
         writable = false;
     }
 
-    exp = nbd_export_new(bs, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL);
+    exp = nbd_export_new(blk, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL);
 
     nbd_export_set_name(exp, device);
 
     n = g_new0(NBDCloseNotifier, 1);
     n->n.notify = nbd_close_notifier;
     n->exp = exp;
-    bdrv_add_close_notifier(bs, &n->n);
+    blk_add_close_notifier(blk, &n->n);
     QTAILQ_INSERT_TAIL(&close_notifiers, n, next);
 }
 
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 9e835d2..348302c 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -85,14 +85,13 @@ int nbd_disconnect(int fd);
 typedef struct NBDExport NBDExport;
 typedef struct NBDClient NBDClient;
 
-NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset,
-                          off_t size, uint32_t nbdflags,
-                          void (*close)(NBDExport *));
+NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
+                          uint32_t nbdflags, void (*close)(NBDExport *));
 void nbd_export_close(NBDExport *exp);
 void nbd_export_get(NBDExport *exp);
 void nbd_export_put(NBDExport *exp);
 
-BlockDriverState *nbd_export_get_blockdev(NBDExport *exp);
+BlockBackend *nbd_export_get_blockdev(NBDExport *exp);
 
 NBDExport *nbd_export_find(const char *name);
 void nbd_export_set_name(NBDExport *exp, const char *name);
diff --git a/nbd.c b/nbd.c
index a7bce45..3fd5743 100644
--- a/nbd.c
+++ b/nbd.c
@@ -19,6 +19,7 @@
 #include "block/nbd.h"
 #include "block/block.h"
 #include "block/block_int.h"
+#include "sysemu/block-backend.h"
 
 #include "block/coroutine.h"
 
@@ -957,10 +958,10 @@ static void bs_aio_detach(void *opaque)
     exp->ctx = NULL;
 }
 
-NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset,
-                          off_t size, uint32_t nbdflags,
-                          void (*close)(NBDExport *))
+NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
+                          uint32_t nbdflags, void (*close)(NBDExport *))
 {
+    BlockDriverState *bs = blk_bs(blk);
     NBDExport *exp = g_malloc0(sizeof(NBDExport));
     exp->refcount = 1;
     QTAILQ_INIT(&exp->clients);
@@ -1056,9 +1057,9 @@ void nbd_export_put(NBDExport *exp)
     }
 }
 
-BlockDriverState *nbd_export_get_blockdev(NBDExport *exp)
+BlockBackend *nbd_export_get_blockdev(NBDExport *exp)
 {
-    return exp->bs;
+    return exp->bs->blk;
 }
 
 void nbd_export_close_all(void)
diff --git a/qemu-nbd.c b/qemu-nbd.c
index 5cd6c6d..60ce50f 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -730,7 +730,7 @@ int main(int argc, char **argv)
         }
     }
 
-    exp = nbd_export_new(bs, dev_offset, fd_size, nbdflags, nbd_export_closed);
+    exp = nbd_export_new(blk, dev_offset, fd_size, nbdflags, nbd_export_closed);
 
     if (sockpath) {
         fd = unix_socket_incoming(sockpath);
-- 
1.9.3

[Qemu-devel] [PATCH v2 5/6] nbd: Use BlockBackend internally

[Max Reitz]

With all externally visible functions changed to use BlockBackend, this
patch makes nbd use BlockBackend for everything internally as well.

While touching them, substitute 512 by BDRV_SECTOR_SIZE in the calls to
blk_read(), blk_write() and blk_co_discard().

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 nbd.c | 56 ++++++++++++++++++++++++++++----------------------------
 1 file changed, 28 insertions(+), 28 deletions(-)

diff --git a/nbd.c b/nbd.c
index 3fd5743..53cf82b 100644
--- a/nbd.c
+++ b/nbd.c
@@ -17,8 +17,6 @@
  */
 
 #include "block/nbd.h"
-#include "block/block.h"
-#include "block/block_int.h"
 #include "sysemu/block-backend.h"
 
 #include "block/coroutine.h"
@@ -102,7 +100,7 @@ struct NBDExport {
     int refcount;
     void (*close)(NBDExport *exp);
 
-    BlockDriverState *bs;
+    BlockBackend *blk;
     char *name;
     off_t dev_offset;
     off_t size;
@@ -930,7 +928,7 @@ static void nbd_request_put(NBDRequest *req)
     nbd_client_put(client);
 }
 
-static void bs_aio_attached(AioContext *ctx, void *opaque)
+static void blk_aio_attached(AioContext *ctx, void *opaque)
 {
     NBDExport *exp = opaque;
     NBDClient *client;
@@ -944,7 +942,7 @@ static void bs_aio_attached(AioContext *ctx, void *opaque)
     }
 }
 
-static void bs_aio_detach(void *opaque)
+static void blk_aio_detach(void *opaque)
 {
     NBDExport *exp = opaque;
     NBDClient *client;
@@ -961,24 +959,23 @@ static void bs_aio_detach(void *opaque)
 NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
                           uint32_t nbdflags, void (*close)(NBDExport *))
 {
-    BlockDriverState *bs = blk_bs(blk);
     NBDExport *exp = g_malloc0(sizeof(NBDExport));
     exp->refcount = 1;
     QTAILQ_INIT(&exp->clients);
-    exp->bs = bs;
+    exp->blk = blk;
     exp->dev_offset = dev_offset;
     exp->nbdflags = nbdflags;
-    exp->size = size == -1 ? bdrv_getlength(bs) : size;
+    exp->size = size == -1 ? blk_getlength(blk) : size;
     exp->close = close;
-    exp->ctx = bdrv_get_aio_context(bs);
-    bdrv_ref(bs);
-    bdrv_add_aio_context_notifier(bs, bs_aio_attached, bs_aio_detach, exp);
+    exp->ctx = blk_get_aio_context(blk);
+    blk_ref(blk);
+    blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
     /*
      * NBD exports are used for non-shared storage migration.  Make sure
      * that BDRV_O_INCOMING is cleared and the image is ready for write
      * access since the export could be available before migration handover.
      */
-    bdrv_invalidate_cache(bs, NULL);
+    blk_invalidate_cache(blk, NULL);
     return exp;
 }
 
@@ -1025,11 +1022,11 @@ void nbd_export_close(NBDExport *exp)
     }
     nbd_export_set_name(exp, NULL);
     nbd_export_put(exp);
-    if (exp->bs) {
-        bdrv_remove_aio_context_notifier(exp->bs, bs_aio_attached,
-                                         bs_aio_detach, exp);
-        bdrv_unref(exp->bs);
-        exp->bs = NULL;
+    if (exp->blk) {
+        blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
+                                        blk_aio_detach, exp);
+        blk_unref(exp->blk);
+        exp->blk = NULL;
     }
 }
 
@@ -1059,7 +1056,7 @@ void nbd_export_put(NBDExport *exp)
 
 BlockBackend *nbd_export_get_blockdev(NBDExport *exp)
 {
-    return exp->bs->blk;
+    return exp->blk;
 }
 
 void nbd_export_close_all(void)
@@ -1138,7 +1135,7 @@ static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *reque
 
     command = request->type & NBD_CMD_MASK_COMMAND;
     if (command == NBD_CMD_READ || command == NBD_CMD_WRITE) {
-        req->data = qemu_blockalign(client->exp->bs, request->len);
+        req->data = blk_blockalign(client->exp->blk, request->len);
     }
     if (command == NBD_CMD_WRITE) {
         TRACE("Reading %u byte(s)", request->len);
@@ -1204,7 +1201,7 @@ static void nbd_trip(void *opaque)
         TRACE("Request type is READ");
 
         if (request.type & NBD_CMD_FLAG_FUA) {
-            ret = bdrv_co_flush(exp->bs);
+            ret = blk_co_flush(exp->blk);
             if (ret < 0) {
                 LOG("flush failed");
                 reply.error = -ret;
@@ -1212,8 +1209,9 @@ static void nbd_trip(void *opaque)
             }
         }
 
-        ret = bdrv_read(exp->bs, (request.from + exp->dev_offset) / 512,
-                        req->data, request.len / 512);
+        ret = blk_read(exp->blk,
+                       (request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
+                       req->data, request.len / BDRV_SECTOR_SIZE);
         if (ret < 0) {
             LOG("reading from file failed");
             reply.error = -ret;
@@ -1235,8 +1233,9 @@ static void nbd_trip(void *opaque)
 
         TRACE("Writing to device");
 
-        ret = bdrv_write(exp->bs, (request.from + exp->dev_offset) / 512,
-                         req->data, request.len / 512);
+        ret = blk_write(exp->blk,
+                        (request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
+                        req->data, request.len / BDRV_SECTOR_SIZE);
         if (ret < 0) {
             LOG("writing to file failed");
             reply.error = -ret;
@@ -1244,7 +1243,7 @@ static void nbd_trip(void *opaque)
         }
 
         if (request.type & NBD_CMD_FLAG_FUA) {
-            ret = bdrv_co_flush(exp->bs);
+            ret = blk_co_flush(exp->blk);
             if (ret < 0) {
                 LOG("flush failed");
                 reply.error = -ret;
@@ -1263,7 +1262,7 @@ static void nbd_trip(void *opaque)
     case NBD_CMD_FLUSH:
         TRACE("Request type is FLUSH");
 
-        ret = bdrv_co_flush(exp->bs);
+        ret = blk_co_flush(exp->blk);
         if (ret < 0) {
             LOG("flush failed");
             reply.error = -ret;
@@ -1274,8 +1273,9 @@ static void nbd_trip(void *opaque)
         break;
     case NBD_CMD_TRIM:
         TRACE("Request type is TRIM");
-        ret = bdrv_co_discard(exp->bs, (request.from + exp->dev_offset) / 512,
-                              request.len / 512);
+        ret = blk_co_discard(exp->blk, (request.from + exp->dev_offset)
+                                       / BDRV_SECTOR_SIZE,
+                             request.len / BDRV_SECTOR_SIZE);
         if (ret < 0) {
             LOG("discard failed");
             reply.error = -ret;
-- 
1.9.3

[Qemu-devel] [PATCH v2 6/6] qemu-nbd: Use BlockBackend where reasonable

[Max Reitz]

Because qemu-nbd creates the BlockBackend by itself, it should create
the according BlockDriverState tree by itself as well; that means, it
has call bdrv_open() on its own. This is one of the places where
qemu-nbd still needs to use a BlockDriverState directly (the root BDS
below the BB); other places are the configuration of zero detection
(which may be lifted into the BB eventually, but is not yet) and
temporarily loading a snapshot.

Everywhere else, though, qemu-nbd can and thus should use BlockBackend.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 qemu-nbd.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/qemu-nbd.c b/qemu-nbd.c
index 60ce50f..d222512 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -146,7 +146,7 @@ static void read_partition(uint8_t *p, struct partition_record *r)
     r->nb_sectors_abs = p[12] | p[13] << 8 | p[14] << 16 | p[15] << 24;
 }
 
-static int find_partition(BlockDriverState *bs, int partition,
+static int find_partition(BlockBackend *blk, int partition,
                           off_t *offset, off_t *size)
 {
     struct partition_record mbr[4];
@@ -155,7 +155,7 @@ static int find_partition(BlockDriverState *bs, int partition,
     int ext_partnum = 4;
     int ret;
 
-    if ((ret = bdrv_read(bs, 0, data, 1)) < 0) {
+    if ((ret = blk_read(blk, 0, data, 1)) < 0) {
         errno = -ret;
         err(EXIT_FAILURE, "error while reading");
     }
@@ -175,7 +175,7 @@ static int find_partition(BlockDriverState *bs, int partition,
             uint8_t data1[512];
             int j;
 
-            if ((ret = bdrv_read(bs, mbr[i].start_sector_abs, data1, 1)) < 0) {
+            if ((ret = blk_read(blk, mbr[i].start_sector_abs, data1, 1)) < 0) {
                 errno = -ret;
                 err(EXIT_FAILURE, "error while reading");
             }
@@ -720,10 +720,10 @@ int main(int argc, char **argv)
     }
 
     bs->detect_zeroes = detect_zeroes;
-    fd_size = bdrv_getlength(bs);
+    fd_size = blk_getlength(blk);
 
     if (partition != -1) {
-        ret = find_partition(bs, partition, &dev_offset, &fd_size);
+        ret = find_partition(blk, partition, &dev_offset, &fd_size);
         if (ret < 0) {
             errno = -ret;
             err(EXIT_FAILURE, "Could not find partition %d", partition);
-- 
1.9.3

Re: [Qemu-devel] [PATCH v2 6/6] qemu-nbd: Use BlockBackend where reasonable

[Paolo Bonzini]

On 18/11/2014 12:21, Max Reitz wrote:
> Because qemu-nbd creates the BlockBackend by itself, it should create
> the according BlockDriverState tree by itself as well; that means, it
> has call bdrv_open() on its own. This is one of the places where
> qemu-nbd still needs to use a BlockDriverState directly (the root BDS
> below the BB); other places are the configuration of zero detection
> (which may be lifted into the BB eventually, but is not yet) and
> temporarily loading a snapshot.
> 
> Everywhere else, though, qemu-nbd can and thus should use BlockBackend.

... which is not much, but is nevertheless a start. :)

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  qemu-nbd.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 60ce50f..d222512 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -146,7 +146,7 @@ static void read_partition(uint8_t *p, struct partition_record *r)
>      r->nb_sectors_abs = p[12] | p[13] << 8 | p[14] << 16 | p[15] << 24;
>  }
>  
> -static int find_partition(BlockDriverState *bs, int partition,
> +static int find_partition(BlockBackend *blk, int partition,
>                            off_t *offset, off_t *size)
>  {
>      struct partition_record mbr[4];
> @@ -155,7 +155,7 @@ static int find_partition(BlockDriverState *bs, int partition,
>      int ext_partnum = 4;
>      int ret;
>  
> -    if ((ret = bdrv_read(bs, 0, data, 1)) < 0) {
> +    if ((ret = blk_read(blk, 0, data, 1)) < 0) {
>          errno = -ret;
>          err(EXIT_FAILURE, "error while reading");
>      }
> @@ -175,7 +175,7 @@ static int find_partition(BlockDriverState *bs, int partition,
>              uint8_t data1[512];
>              int j;
>  
> -            if ((ret = bdrv_read(bs, mbr[i].start_sector_abs, data1, 1)) < 0) {
> +            if ((ret = blk_read(blk, mbr[i].start_sector_abs, data1, 1)) < 0) {
>                  errno = -ret;
>                  err(EXIT_FAILURE, "error while reading");
>              }
> @@ -720,10 +720,10 @@ int main(int argc, char **argv)
>      }
>  
>      bs->detect_zeroes = detect_zeroes;
> -    fd_size = bdrv_getlength(bs);
> +    fd_size = blk_getlength(blk);
>  
>      if (partition != -1) {
> -        ret = find_partition(bs, partition, &dev_offset, &fd_size);
> +        ret = find_partition(blk, partition, &dev_offset, &fd_size);
>          if (ret < 0) {
>              errno = -ret;
>              err(EXIT_FAILURE, "Could not find partition %d", partition);
> 

Re: [Qemu-devel] [PATCH v2 0/6] nbd: Use BlockBackend

[Stefan Hajnoczi]

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On Tue, Nov 18, 2014 at 12:21:13PM +0100, Max Reitz wrote:
> From the block layer's perspective, the nbd server is pretty similar to
> a guest device. Therefore, it should use BlockBackend to access block
> devices, just like any other guest device does.
> 
> This series consequently makes the nbd server use BlockBackend for
> referencing block devices.
> 
> 
> v2:
> - Added patch 6, which converts qemu-nbd to BlockBackend as far as
>   reasonable [Paolo]
> 
> 
> git-backport-diff against v1:
> 
> Key:
> [----] : patches are identical
> [####] : number of functional differences between upstream/downstream patch
> [down] : patch is downstream-only
> The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively
> 
> 001/6:[----] [--] 'block: Lift more functions into BlockBackend'
> 002/6:[----] [--] 'block: Add AioContextNotifier functions to BB'
> 003/6:[----] [--] 'block: Add blk_add_close_notifier() for BB'
> 004/6:[----] [--] 'nbd: Change external interface to BlockBackend'
> 005/6:[----] [--] 'nbd: Use BlockBackend internally'
> 006/6:[down] 'qemu-nbd: Use BlockBackend where reasonable'
> 
> 
> Max Reitz (6):
>   block: Lift more functions into BlockBackend
>   block: Add AioContextNotifier functions to BB
>   block: Add blk_add_close_notifier() for BB
>   nbd: Change external interface to BlockBackend
>   nbd: Use BlockBackend internally
>   qemu-nbd: Use BlockBackend where reasonable
> 
>  block/block-backend.c          | 38 +++++++++++++++++++++++++
>  blockdev-nbd.c                 | 15 +++++-----
>  include/block/nbd.h            |  7 ++---
>  include/sysemu/block-backend.h | 12 ++++++++
>  nbd.c                          | 63 +++++++++++++++++++++---------------------
>  qemu-nbd.c                     | 12 ++++----
>  6 files changed, 99 insertions(+), 48 deletions(-)
> 
> -- 
> 1.9.3
> 
> 

Thanks, applied to my block-next tree:
https://github.com/stefanha/qemu/commits/block-next

Stefan

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