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block, block-backend: write some hot coroutine wrappers by hand

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The introduction of the graph lock is causing blk_get_geometry, a hot function
used in the I/O path, to create a coroutine.  However, the only part that really
needs to run in coroutine context is the call to bdrv_co_refresh_total_sectors,
which in turn only happens in the rare case of host CD-ROM devices.

So, write by hand the three wrappers on the path from blk_co_get_geometry to
bdrv_co_refresh_total_sectors, so that the coroutine wrapper is only created
if bdrv_nb_sectors actually calls bdrv_refresh_total_sectors.

Reported-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20230407153303.391121-9-pbonzini@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2023-04-07 17:33:03 +02:00 • committed by Kevin Wolf
parent 9ed98cae15
commit 81f730d4d0
4 changed files with 52 additions and 4 deletions
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22
block.c
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@ -5859,6 +5859,28 @@ int64_t coroutine_fn bdrv_co_nb_sectors(BlockDriverState *bs)
return bs->total_sectors;
}
/*
* This wrapper is written by hand because this function is in the hot I/O path,
* via blk_get_geometry.
*/
int64_t coroutine_mixed_fn bdrv_nb_sectors(BlockDriverState *bs)
{
BlockDriver *drv = bs->drv;
IO_CODE();
if (!drv)
return -ENOMEDIUM;
if (bs->bl.has_variable_length) {
int ret = bdrv_refresh_total_sectors(bs, bs->total_sectors);
if (ret < 0) {
return ret;
}
}
return bs->total_sectors;
}
/**
* Return length in bytes on success, -errno on error.
* The length is always a multiple of BDRV_SECTOR_SIZE.