[02/17] block: Introduce bdrv_driver_pwritev()
diff mbox

Message ID 1461750767-23273-3-git-send-email-kwolf@redhat.com
State New
Headers show

Commit Message

Kevin Wolf April 27, 2016, 9:52 a.m. UTC
This is a function that simply calls into the block driver for doing a
write, providing the byte granularity interface we want to eventually
have everywhere, and using whatever interface that driver supports.

This one is a bit more interesting that the version for reads: It adds
support for .bdrv_co_writev_flags() everywhere, so that drivers
implementing this function can drop .bdrv_co_writev() now.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/io.c      | 51 ++++++++++++++++++++++++++++++++++++---------------
 block/iscsi.c   |  8 --------
 block/nbd.c     |  9 ---------
 block/raw_bsd.c |  8 --------
 4 files changed, 36 insertions(+), 40 deletions(-)

Comments

Eric Blake April 27, 2016, 2:03 p.m. UTC | #1
On 04/27/2016 03:52 AM, Kevin Wolf wrote:
> This is a function that simply calls into the block driver for doing a
> write, providing the byte granularity interface we want to eventually
> have everywhere, and using whatever interface that driver supports.
> 
> This one is a bit more interesting that the version for reads: It adds
> support for .bdrv_co_writev_flags() everywhere, so that drivers
> implementing this function can drop .bdrv_co_writev() now.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/io.c      | 51 ++++++++++++++++++++++++++++++++++++---------------
>  block/iscsi.c   |  8 --------
>  block/nbd.c     |  9 ---------
>  block/raw_bsd.c |  8 --------
>  4 files changed, 36 insertions(+), 40 deletions(-)
> 
>  
> +static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
> +                                            uint64_t offset, uint64_t bytes,
> +                                            QEMUIOVector *qiov, int flags)
> +{
> +    BlockDriver *drv = bs->drv;
> +    int64_t sector_num = offset >> BDRV_SECTOR_BITS;
> +    unsigned int nb_sectors = bytes >> BDRV_SECTOR_BITS;
> +    int ret;
> +
> +    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS);
> +
> +    if (drv->bdrv_co_writev_flags) {
> +        ret = drv->bdrv_co_writev_flags(bs, sector_num, nb_sectors, qiov,
> +                                        flags);

Not for this patch, but should we be doing something like assert((flags
& ~drv->supported_write_flags) == 0)?

> +    } else {
> +        assert(drv->supported_write_flags == 0);
> +        ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);
> +    }
> +
> +    if (ret == 0 && (flags & BDRV_REQ_FUA) &&
> +        !(drv->supported_write_flags & BDRV_REQ_FUA))
> +    {
> +        ret = bdrv_co_flush(bs);

Unrelated to your patch here, but in my NBD work, I ran into the
situation where it would be nicer if drv->supported_write_flags were
dynamic.  That is, an NBD client can tell on a per-connection basis
whether the server supports NBD_FLAG_FUA, but because
supported_write_flags is a property of the driver, rather than a
callback that is a function of the bs, NBD has to reflect it back to the
block layer by advertising supported_write_flags == BDRV_REQ_FUA always,
and when connecting to a less-capable server has to manually repeat the
bdrv_co_flush(bs) fallback dance itself:

http://git.qemu.org/?p=qemu.git;a=blob;f=block/nbd.c;h=f7ea3b3608;hb=3123bd8e#l358

Maybe we should do a patch series that converts supported_write_flags to
be a function call that can have per-bs configuration, so that the NBD
client can be simplified by letting the block layer take care of the FUA
fallback.

> @@ -1215,23 +1247,12 @@ static int coroutine_fn bdrv_aligned_pwritev(BlockDriverState *bs,
>      } else if (flags & BDRV_REQ_ZERO_WRITE) {
>          bdrv_debug_event(bs, BLKDBG_PWRITEV_ZERO);
>          ret = bdrv_co_do_write_zeroes(bs, sector_num, nb_sectors, flags);
> -    } else if (drv->bdrv_co_writev_flags) {
> -        bdrv_debug_event(bs, BLKDBG_PWRITEV);
> -        ret = drv->bdrv_co_writev_flags(bs, sector_num, nb_sectors, qiov,
> -                                        flags);

Should bdrv_co_do_write_zeroes also be folded into bdrv_driver_pwritev()?

But what you have looks sane enough for:
Reviewed-by: Eric Blake <eblake@redhat.com>

Patch
diff mbox

diff --git a/block/io.c b/block/io.c
index 586a46a..c9b2864 100644
--- a/block/io.c
+++ b/block/io.c
@@ -815,6 +815,36 @@  static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
     return drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
 }
 
+static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
+                                            uint64_t offset, uint64_t bytes,
+                                            QEMUIOVector *qiov, int flags)
+{
+    BlockDriver *drv = bs->drv;
+    int64_t sector_num = offset >> BDRV_SECTOR_BITS;
+    unsigned int nb_sectors = bytes >> BDRV_SECTOR_BITS;
+    int ret;
+
+    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
+    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
+    assert((bytes >> BDRV_SECTOR_BITS) <= BDRV_REQUEST_MAX_SECTORS);
+
+    if (drv->bdrv_co_writev_flags) {
+        ret = drv->bdrv_co_writev_flags(bs, sector_num, nb_sectors, qiov,
+                                        flags);
+    } else {
+        assert(drv->supported_write_flags == 0);
+        ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);
+    }
+
+    if (ret == 0 && (flags & BDRV_REQ_FUA) &&
+        !(drv->supported_write_flags & BDRV_REQ_FUA))
+    {
+        ret = bdrv_co_flush(bs);
+    }
+
+    return ret;
+}
+
 static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
 {
@@ -866,8 +896,9 @@  static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
         /* This does not change the data on the disk, it is not necessary
          * to flush even in cache=writethrough mode.
          */
-        ret = drv->bdrv_co_writev(bs, cluster_sector_num, cluster_nb_sectors,
-                                  &bounce_qiov);
+        ret = bdrv_driver_pwritev(bs, cluster_sector_num * BDRV_SECTOR_SIZE,
+                                  cluster_nb_sectors * BDRV_SECTOR_SIZE,
+                                  &bounce_qiov, 0);
     }
 
     if (ret < 0) {
@@ -1155,7 +1186,8 @@  static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
             }
             qemu_iovec_init_external(&qiov, &iov, 1);
 
-            ret = drv->bdrv_co_writev(bs, sector_num, num, &qiov);
+            ret = bdrv_driver_pwritev(bs, sector_num * BDRV_SECTOR_SIZE,
+                                      num * BDRV_SECTOR_SIZE, &qiov, 0);
 
             /* Keep bounce buffer around if it is big enough for all
              * all future requests.
@@ -1215,23 +1247,12 @@  static int coroutine_fn bdrv_aligned_pwritev(BlockDriverState *bs,
     } else if (flags & BDRV_REQ_ZERO_WRITE) {
         bdrv_debug_event(bs, BLKDBG_PWRITEV_ZERO);
         ret = bdrv_co_do_write_zeroes(bs, sector_num, nb_sectors, flags);
-    } else if (drv->bdrv_co_writev_flags) {
-        bdrv_debug_event(bs, BLKDBG_PWRITEV);
-        ret = drv->bdrv_co_writev_flags(bs, sector_num, nb_sectors, qiov,
-                                        flags);
     } else {
-        assert(drv->supported_write_flags == 0);
         bdrv_debug_event(bs, BLKDBG_PWRITEV);
-        ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);
+        ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, flags);
     }
     bdrv_debug_event(bs, BLKDBG_PWRITEV_DONE);
 
-    if (ret == 0 && (flags & BDRV_REQ_FUA) &&
-        !(drv->supported_write_flags & BDRV_REQ_FUA))
-    {
-        ret = bdrv_co_flush(bs);
-    }
-
     bdrv_set_dirty(bs, sector_num, nb_sectors);
 
     if (bs->wr_highest_offset < offset + bytes) {
diff --git a/block/iscsi.c b/block/iscsi.c
index 302baf8..4f75204 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -513,13 +513,6 @@  retry:
     return 0;
 }
 
-static int coroutine_fn
-iscsi_co_writev(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
-                QEMUIOVector *iov)
-{
-    return iscsi_co_writev_flags(bs, sector_num, nb_sectors, iov, 0);
-}
-
 
 static bool iscsi_allocationmap_is_allocated(IscsiLun *iscsilun,
                                              int64_t sector_num, int nb_sectors)
@@ -1847,7 +1840,6 @@  static BlockDriver bdrv_iscsi = {
     .bdrv_co_discard      = iscsi_co_discard,
     .bdrv_co_write_zeroes = iscsi_co_write_zeroes,
     .bdrv_co_readv         = iscsi_co_readv,
-    .bdrv_co_writev        = iscsi_co_writev,
     .bdrv_co_writev_flags  = iscsi_co_writev_flags,
     .supported_write_flags = BDRV_REQ_FUA,
     .bdrv_co_flush_to_disk = iscsi_co_flush,
diff --git a/block/nbd.c b/block/nbd.c
index f7ea3b3..fccbfef 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -374,12 +374,6 @@  static int nbd_co_writev_flags(BlockDriverState *bs, int64_t sector_num,
     return ret;
 }
 
-static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num,
-                         int nb_sectors, QEMUIOVector *qiov)
-{
-    return nbd_co_writev_flags(bs, sector_num, nb_sectors, qiov, 0);
-}
-
 static int nbd_co_flush(BlockDriverState *bs)
 {
     return nbd_client_co_flush(bs);
@@ -476,7 +470,6 @@  static BlockDriver bdrv_nbd = {
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,
     .bdrv_co_readv              = nbd_co_readv,
-    .bdrv_co_writev             = nbd_co_writev,
     .bdrv_co_writev_flags       = nbd_co_writev_flags,
     .supported_write_flags      = BDRV_REQ_FUA,
     .bdrv_close                 = nbd_close,
@@ -496,7 +489,6 @@  static BlockDriver bdrv_nbd_tcp = {
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,
     .bdrv_co_readv              = nbd_co_readv,
-    .bdrv_co_writev             = nbd_co_writev,
     .bdrv_co_writev_flags       = nbd_co_writev_flags,
     .supported_write_flags      = BDRV_REQ_FUA,
     .bdrv_close                 = nbd_close,
@@ -516,7 +508,6 @@  static BlockDriver bdrv_nbd_unix = {
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,
     .bdrv_co_readv              = nbd_co_readv,
-    .bdrv_co_writev             = nbd_co_writev,
     .bdrv_co_writev_flags       = nbd_co_writev_flags,
     .supported_write_flags      = BDRV_REQ_FUA,
     .bdrv_close                 = nbd_close,
diff --git a/block/raw_bsd.c b/block/raw_bsd.c
index a6cc7e9..9c9d39b 100644
--- a/block/raw_bsd.c
+++ b/block/raw_bsd.c
@@ -116,13 +116,6 @@  fail:
     return ret;
 }
 
-static int coroutine_fn
-raw_co_writev(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
-              QEMUIOVector *qiov)
-{
-    return raw_co_writev_flags(bs, sector_num, nb_sectors, qiov, 0);
-}
-
 static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
                                             int64_t sector_num,
                                             int nb_sectors, int *pnum,
@@ -256,7 +249,6 @@  BlockDriver bdrv_raw = {
     .bdrv_close           = &raw_close,
     .bdrv_create          = &raw_create,
     .bdrv_co_readv        = &raw_co_readv,
-    .bdrv_co_writev       = &raw_co_writev,
     .bdrv_co_writev_flags = &raw_co_writev_flags,
     .supported_write_flags = BDRV_REQ_FUA,
     .bdrv_co_write_zeroes = &raw_co_write_zeroes,