[Qemu-devel] [PATCH 0/2] block: block driver callbacks fixes

[Qemu-devel] [PATCH 0/2] block: block driver callbacks fixes

[Manos Pitsidianakis]

This series makes implementing some of the bdrv_* callbacks easier for block
drivers by passing requests to bs->file if bs->drv doesn't implement it instead
of failing, and adding default bdrv_co_get_block_status() implementations.

This based against Kevin Wolf's block branch, commit
0dd2ec6bc46bd93ea0b9df602962883417f31400

Manos Pitsidianakis (2):
  block: pass bdrv_* methods to bs->file by default
  block: add default implementations for bdrv_co_get_block_status()

 block.c                   | 45 ++++++++++++++++++++++++++++++++++-----------
 block/blkdebug.c          | 12 +-----------
 block/commit.c            | 12 +-----------
 block/io.c                | 28 ++++++++++++++++++++++++++++
 block/mirror.c            | 12 +-----------
 include/block/block_int.h | 16 ++++++++++++++++
 6 files changed, 81 insertions(+), 44 deletions(-)

-- 
2.11.0

[Qemu-devel] [PATCH 1/2] block: pass bdrv_* methods to bs->file by default

[Manos Pitsidianakis]

The following functions fail if bs->drv does not implement them:

bdrv_probe_blocksizes
bdrv_probe_geometry
bdrv_truncate
bdrv_has_zero_init
bdrv_get_info
bdrv_media_changed
bdrv_eject
bdrv_lock_medium
bdrv_co_ioctl

Instead, the call should be passed to bs->file if it exists, to allow
filter drivers to support those methods without implementing them.

Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
---
 block.c    | 45 ++++++++++++++++++++++++++++++++++-----------
 block/io.c |  4 ++++
 2 files changed, 38 insertions(+), 11 deletions(-)

diff --git a/block.c b/block.c
index 69439628..ad11230a 100644
--- a/block.c
+++ b/block.c
@@ -494,6 +494,8 @@ int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
 
     if (drv && drv->bdrv_probe_blocksizes) {
         return drv->bdrv_probe_blocksizes(bs, bsz);
+    } else if (bs->file && bs->file->bs) {
+        return bdrv_probe_blocksizes(bs->file->bs, bsz);
     }
 
     return -ENOTSUP;
@@ -511,6 +513,8 @@ int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo)
 
     if (drv && drv->bdrv_probe_geometry) {
         return drv->bdrv_probe_geometry(bs, geo);
+    } else if (bs->file && bs->file->bs) {
+        return bdrv_probe_geometry(bs->file->bs, geo);
     }
 
     return -ENOTSUP;
@@ -3406,13 +3410,18 @@ int bdrv_truncate(BdrvChild *child, int64_t offset, Error **errp)
 
     assert(child->perm & BLK_PERM_RESIZE);
 
-    if (!drv) {
-        error_setg(errp, "No medium inserted");
-        return -ENOMEDIUM;
-    }
-    if (!drv->bdrv_truncate) {
-        error_setg(errp, "Image format driver does not support resize");
-        return -ENOTSUP;
+    if (!drv || !drv->bdrv_truncate) {
+        if (bs->file && bs->file->bs) {
+            return bdrv_truncate(bs->file, offset, errp);
+        }
+        if (!drv) {
+            error_setg(errp, "No medium inserted");
+            return -ENOMEDIUM;
+        }
+        if (!drv->bdrv_truncate) {
+            error_setg(errp, "Image format driver does not support resize");
+            return -ENOTSUP;
+        }
     }
     if (bs->read_only) {
         error_setg(errp, "Image is read-only");
@@ -3778,6 +3787,9 @@ int bdrv_has_zero_init(BlockDriverState *bs)
     if (bs->drv->bdrv_has_zero_init) {
         return bs->drv->bdrv_has_zero_init(bs);
     }
+    if (bs->file && bs->file->bs) {
+        return bdrv_has_zero_init(bs->file->bs);
+    }
 
     /* safe default */
     return 0;
@@ -3832,10 +3844,15 @@ void bdrv_get_backing_filename(BlockDriverState *bs,
 int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
 {
     BlockDriver *drv = bs->drv;
-    if (!drv)
-        return -ENOMEDIUM;
-    if (!drv->bdrv_get_info)
-        return -ENOTSUP;
+    if (!drv || !drv->bdrv_get_info) {
+        if (bs->file && bs->file->bs) {
+            return bdrv_get_info(bs->file->bs, bdi);
+        }
+        if (!drv)
+            return -ENOMEDIUM;
+        if (!drv->bdrv_get_info)
+            return -ENOTSUP;
+    }
     memset(bdi, 0, sizeof(*bdi));
     return drv->bdrv_get_info(bs, bdi);
 }
@@ -4205,6 +4222,8 @@ int bdrv_media_changed(BlockDriverState *bs)
 
     if (drv && drv->bdrv_media_changed) {
         return drv->bdrv_media_changed(bs);
+    } else if (bs->file && bs->file->bs) {
+        bdrv_media_changed(bs->file->bs);
     }
     return -ENOTSUP;
 }
@@ -4218,6 +4237,8 @@ void bdrv_eject(BlockDriverState *bs, bool eject_flag)
 
     if (drv && drv->bdrv_eject) {
         drv->bdrv_eject(bs, eject_flag);
+    } else if (bs->file && bs->file->bs) {
+        bdrv_eject(bs->file->bs, eject_flag);
     }
 }
 
@@ -4233,6 +4254,8 @@ void bdrv_lock_medium(BlockDriverState *bs, bool locked)
 
     if (drv && drv->bdrv_lock_medium) {
         drv->bdrv_lock_medium(bs, locked);
+    } else if (bs->file && bs->file->bs) {
+        bdrv_lock_medium(bs->file->bs, locked);
     }
 }
 
diff --git a/block/io.c b/block/io.c
index c72d7015..c1b73226 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2403,6 +2403,10 @@ int bdrv_co_ioctl(BlockDriverState *bs, int req, void *buf)
 
     bdrv_inc_in_flight(bs);
     if (!drv || (!drv->bdrv_aio_ioctl && !drv->bdrv_co_ioctl)) {
+        if (bs->file && bs->file->bs) {
+            bdrv_dec_in_flight(bs);
+            return bdrv_co_ioctl(bs->file->bs, req, buf);
+        }
         co.ret = -ENOTSUP;
         goto out;
     }
-- 
2.11.0

[Qemu-devel] [PATCH 2/2] block: add default implementations for bdrv_co_get_block_status()

[Manos Pitsidianakis]

bdrv_co_get_block_status_from_file() and
bdrv_co_get_block_status_from_backing() set *file to bs->file and
bs->backing respectively, so that bdrv_co_get_block_status() can recurse
to them. Future block drivers won't have to duplicate code to implement
this.

Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
---
 block/blkdebug.c          | 12 +-----------
 block/commit.c            | 12 +-----------
 block/io.c                | 24 ++++++++++++++++++++++++
 block/mirror.c            | 12 +-----------
 include/block/block_int.h | 16 ++++++++++++++++
 5 files changed, 43 insertions(+), 33 deletions(-)

diff --git a/block/blkdebug.c b/block/blkdebug.c
index b25856c4..f1539db6 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -641,16 +641,6 @@ static int coroutine_fn blkdebug_co_pdiscard(BlockDriverState *bs,
     return bdrv_co_pdiscard(bs->file->bs, offset, bytes);
 }
 
-static int64_t coroutine_fn blkdebug_co_get_block_status(
-    BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum,
-    BlockDriverState **file)
-{
-    *pnum = nb_sectors;
-    *file = bs->file->bs;
-    return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID |
-        (sector_num << BDRV_SECTOR_BITS);
-}
-
 static void blkdebug_close(BlockDriverState *bs)
 {
     BDRVBlkdebugState *s = bs->opaque;
@@ -925,7 +915,7 @@ static BlockDriver bdrv_blkdebug = {
     .bdrv_co_flush_to_disk  = blkdebug_co_flush,
     .bdrv_co_pwrite_zeroes  = blkdebug_co_pwrite_zeroes,
     .bdrv_co_pdiscard       = blkdebug_co_pdiscard,
-    .bdrv_co_get_block_status = blkdebug_co_get_block_status,
+    .bdrv_co_get_block_status = bdrv_co_get_block_status_from_file,
 
     .bdrv_debug_event           = blkdebug_debug_event,
     .bdrv_debug_breakpoint      = blkdebug_debug_breakpoint,
diff --git a/block/commit.c b/block/commit.c
index 524bd549..5b04f832 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -247,16 +247,6 @@ static int coroutine_fn bdrv_commit_top_preadv(BlockDriverState *bs,
     return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
 }
 
-static int64_t coroutine_fn bdrv_commit_top_get_block_status(
-    BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum,
-    BlockDriverState **file)
-{
-    *pnum = nb_sectors;
-    *file = bs->backing->bs;
-    return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID |
-           (sector_num << BDRV_SECTOR_BITS);
-}
-
 static void bdrv_commit_top_refresh_filename(BlockDriverState *bs, QDict *opts)
 {
     bdrv_refresh_filename(bs->backing->bs);
@@ -282,7 +272,7 @@ static void bdrv_commit_top_child_perm(BlockDriverState *bs, BdrvChild *c,
 static BlockDriver bdrv_commit_top = {
     .format_name                = "commit_top",
     .bdrv_co_preadv             = bdrv_commit_top_preadv,
-    .bdrv_co_get_block_status   = bdrv_commit_top_get_block_status,
+    .bdrv_co_get_block_status   = bdrv_co_get_block_status_from_backing,
     .bdrv_refresh_filename      = bdrv_commit_top_refresh_filename,
     .bdrv_close                 = bdrv_commit_top_close,
     .bdrv_child_perm            = bdrv_commit_top_child_perm,
diff --git a/block/io.c b/block/io.c
index c1b73226..aec520b4 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1706,6 +1706,30 @@ typedef struct BdrvCoGetBlockStatusData {
     bool done;
 } BdrvCoGetBlockStatusData;
 
+int64_t coroutine_fn bdrv_co_get_block_status_from_file(BlockDriverState *bs,
+                                                     int64_t sector_num,
+                                                     int nb_sectors, int *pnum,
+                                                     BlockDriverState **file)
+{
+    assert(bs->file && bs->file->bs);
+    *pnum = nb_sectors;
+    *file = bs->file->bs;
+    return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID |
+           (sector_num << BDRV_SECTOR_BITS);
+}
+
+int64_t coroutine_fn bdrv_co_get_block_status_from_backing(BlockDriverState *bs,
+                                                     int64_t sector_num,
+                                                     int nb_sectors, int *pnum,
+                                                     BlockDriverState **file)
+{
+    assert(bs->backing && bs->backing->bs);
+    *pnum = nb_sectors;
+    *file = bs->backing->bs;
+    return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID |
+           (sector_num << BDRV_SECTOR_BITS);
+}
+
 /*
  * Returns the allocation status of the specified sectors.
  * Drivers not implementing the functionality are assumed to not support
diff --git a/block/mirror.c b/block/mirror.c
index 61a862dc..e8bf5f40 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -1052,16 +1052,6 @@ static int coroutine_fn bdrv_mirror_top_flush(BlockDriverState *bs)
     return bdrv_co_flush(bs->backing->bs);
 }
 
-static int64_t coroutine_fn bdrv_mirror_top_get_block_status(
-    BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum,
-    BlockDriverState **file)
-{
-    *pnum = nb_sectors;
-    *file = bs->backing->bs;
-    return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID |
-           (sector_num << BDRV_SECTOR_BITS);
-}
-
 static int coroutine_fn bdrv_mirror_top_pwrite_zeroes(BlockDriverState *bs,
     int64_t offset, int bytes, BdrvRequestFlags flags)
 {
@@ -1108,7 +1098,7 @@ static BlockDriver bdrv_mirror_top = {
     .bdrv_co_pwrite_zeroes      = bdrv_mirror_top_pwrite_zeroes,
     .bdrv_co_pdiscard           = bdrv_mirror_top_pdiscard,
     .bdrv_co_flush              = bdrv_mirror_top_flush,
-    .bdrv_co_get_block_status   = bdrv_mirror_top_get_block_status,
+    .bdrv_co_get_block_status   = bdrv_co_get_block_status_from_backing,
     .bdrv_refresh_filename      = bdrv_mirror_top_refresh_filename,
     .bdrv_close                 = bdrv_mirror_top_close,
     .bdrv_child_perm            = bdrv_mirror_top_child_perm,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 15fa6021..a42c2a6f 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -945,6 +945,22 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
                                uint64_t perm, uint64_t shared,
                                uint64_t *nperm, uint64_t *nshared);
 
+/*
+ * Default implementation for drivers to pass bdrv_co_get_block_status() to
+ * their file
+ * */
+int64_t coroutine_fn bdrv_co_get_block_status_from_file(BlockDriverState *bs,
+                                                     int64_t sector_num,
+                                                     int nb_sectors, int *pnum,
+                                                     BlockDriverState **file);
+/*
+ * Default implementation for drivers to pass bdrv_co_get_block_status() to
+ * their backing file
+ * */
+int64_t coroutine_fn bdrv_co_get_block_status_from_backing(BlockDriverState *bs,
+                                                     int64_t sector_num,
+                                                     int nb_sectors, int *pnum,
+                                                     BlockDriverState **file);
 const char *bdrv_get_parent_name(const BlockDriverState *bs);
 void blk_dev_change_media_cb(BlockBackend *blk, bool load, Error **errp);
 bool blk_dev_has_removable_media(BlockBackend *blk);
-- 
2.11.0

Re: [Qemu-devel] [Qemu-block] [PATCH 1/2] block: pass bdrv_* methods to bs->file by default

[Stefan Hajnoczi]

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On Wed, Jun 28, 2017 at 01:46:15AM +0300, Manos Pitsidianakis wrote:
> @@ -3406,13 +3410,18 @@ int bdrv_truncate(BdrvChild *child, int64_t offset, Error **errp)
>  
>      assert(child->perm & BLK_PERM_RESIZE);
>  
> -    if (!drv) {
> -        error_setg(errp, "No medium inserted");
> -        return -ENOMEDIUM;
> -    }
> -    if (!drv->bdrv_truncate) {
> -        error_setg(errp, "Image format driver does not support resize");
> -        return -ENOTSUP;
> +    if (!drv || !drv->bdrv_truncate) {

bs->drv == NULL means the BDS is closed.  We should not forward to
bs->file.  In practice bs->file will be NULL but please leave the
original if statement unchanged so it's clear that !drv results in
-ENOMEDIUM.

The same applies to the other changes below.

> @@ -3832,10 +3844,15 @@ void bdrv_get_backing_filename(BlockDriverState *bs,
>  int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
>  {
>      BlockDriver *drv = bs->drv;
> -    if (!drv)
> -        return -ENOMEDIUM;
> -    if (!drv->bdrv_get_info)
> -        return -ENOTSUP;
> +    if (!drv || !drv->bdrv_get_info) {
> +        if (bs->file && bs->file->bs) {
> +            return bdrv_get_info(bs->file->bs, bdi);
> +        }
> +        if (!drv)
> +            return -ENOMEDIUM;

QEMU coding style always uses curly braces, even when the if statement
body is just 1 line.

> diff --git a/block/io.c b/block/io.c
> index c72d7015..c1b73226 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -2403,6 +2403,10 @@ int bdrv_co_ioctl(BlockDriverState *bs, int req, void *buf)
>  
>      bdrv_inc_in_flight(bs);
>      if (!drv || (!drv->bdrv_aio_ioctl && !drv->bdrv_co_ioctl)) {
> +        if (bs->file && bs->file->bs) {
> +            bdrv_dec_in_flight(bs);
> +            return bdrv_co_ioctl(bs->file->bs, req, buf);

bdrv_dec_in_flight() must happen after the request finishes, otherwise
bdrv_drain() will break.

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Re: [Qemu-devel] [Qemu-block] [PATCH 2/2] block: add default implementations for bdrv_co_get_block_status()

[Stefan Hajnoczi]

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On Wed, Jun 28, 2017 at 01:46:16AM +0300, Manos Pitsidianakis wrote:
> bdrv_co_get_block_status_from_file() and
> bdrv_co_get_block_status_from_backing() set *file to bs->file and
> bs->backing respectively, so that bdrv_co_get_block_status() can recurse
> to them. Future block drivers won't have to duplicate code to implement
> this.
> 
> Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
> ---
>  block/blkdebug.c          | 12 +-----------
>  block/commit.c            | 12 +-----------
>  block/io.c                | 24 ++++++++++++++++++++++++
>  block/mirror.c            | 12 +-----------
>  include/block/block_int.h | 16 ++++++++++++++++
>  5 files changed, 43 insertions(+), 33 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [Qemu-block] [PATCH 1/2] block: pass bdrv_* methods to bs->file by default

[Stefan Hajnoczi]

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On Wed, Jun 28, 2017 at 01:46:15AM +0300, Manos Pitsidianakis wrote:
> The following functions fail if bs->drv does not implement them:
> 
> bdrv_probe_blocksizes
> bdrv_probe_geometry
> bdrv_truncate
> bdrv_has_zero_init
> bdrv_get_info
> bdrv_media_changed
> bdrv_eject
> bdrv_lock_medium
> bdrv_co_ioctl
> 
> Instead, the call should be passed to bs->file if it exists, to allow
> filter drivers to support those methods without implementing them.
> 
> Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
> ---
>  block.c    | 45 ++++++++++++++++++++++++++++++++++-----------
>  block/io.c |  4 ++++
>  2 files changed, 38 insertions(+), 11 deletions(-)

Will you send a block/raw-format.c patch that removes the forwarding
functions that are no longer needed?

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Re: [Qemu-devel] [Qemu-block] [PATCH 1/2] block: pass bdrv_* methods to bs->file by default

[Eric Blake]

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On 06/29/2017 09:05 AM, Stefan Hajnoczi wrote:
> On Wed, Jun 28, 2017 at 01:46:15AM +0300, Manos Pitsidianakis wrote:
>> The following functions fail if bs->drv does not implement them:
>>
>> bdrv_probe_blocksizes
>> bdrv_probe_geometry
>> bdrv_truncate
>> bdrv_has_zero_init
>> bdrv_get_info
>> bdrv_media_changed
>> bdrv_eject
>> bdrv_lock_medium
>> bdrv_co_ioctl
>>
>> Instead, the call should be passed to bs->file if it exists, to allow
>> filter drivers to support those methods without implementing them.
>>
>> Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
>> ---
>>  block.c    | 45 ++++++++++++++++++++++++++++++++++-----------
>>  block/io.c |  4 ++++
>>  2 files changed, 38 insertions(+), 11 deletions(-)
> 
> Will you send a block/raw-format.c patch that removes the forwarding
> functions that are no longer needed?

block/raw-format.c does some additional things thanks to its 'offset'
parameter, so I think it will have to still implement things directly
rather than relying on defaults.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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