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block: Fix in_flight leak in request padding error path

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When bdrv_pad_request() fails in bdrv_co_preadv_part(), bs->in_flight
has been increased, but is never decreased again. This leads to a hang
when trying to drain the block node.

This bug was observed with Windows guests which issue a request that
fully uses IOV_MAX during installation, so that when padding is
necessary (O_DIRECT with a 4k sector size block device on the host),
adding another entry causes failure.

Call bdrv_dec_in_flight() to fix this. There is a larger problem to
solve here because this request shouldn't even fail, but Windows doesn't
seem to care and with this minimal fix the installation succeeds. So
given that we're already in freeze, let's take this minimal fix for 6.1.

Fixes: 98ca45494f
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1972079
Reported-by: Qing Wang <qinwang@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210727154923.91067-1-kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2021-07-27 17:49:23 +02:00
parent 7f1cab9c62
commit 87ab880252
1 changed files with 4 additions and 3 deletions
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7
block/io.c
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@ -1841,7 +1841,7 @@ int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
ret = bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad,
NULL);
if (ret < 0) {
return ret;
goto fail;
}
tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_READ);
@ -1849,10 +1849,11 @@ int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
bs->bl.request_alignment,
qiov, qiov_offset, flags);
tracked_request_end(&req);
bdrv_dec_in_flight(bs);
bdrv_padding_destroy(&pad);
fail:
bdrv_dec_in_flight(bs);
return ret;
}