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From 1bf03e66fd03af46ff0f98dd04b6e28f432ac1e3 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Fri, 7 Apr 2017 12:29:05 +0200
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Subject: [PATCH] block: Don't check permissions for copy on read
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The assertion is currently failing. We can't require callers to have
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write permissions when all they are doing is a read, so comment it out.
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Add a FIXME comment in the code so that the check is re-enabled when
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copy on read is refactored into its own filter driver.
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Reported-by: Richard W.M. Jones <rjones@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
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---
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block/io.c | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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diff --git a/block/io.c b/block/io.c
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index 2709a7007f..7321ddab3d 100644
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--- a/block/io.c
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+++ b/block/io.c
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@@ -945,7 +945,14 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
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size_t skip_bytes;
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int ret;
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- assert(child->perm & (BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE));
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+ /* FIXME We cannot require callers to have write permissions when all they
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+ * are doing is a read request. If we did things right, write permissions
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+ * would be obtained anyway, but internally by the copy-on-read code. As
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+ * long as it is implemented here rather than in a separat filter driver,
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+ * the copy-on-read code doesn't have its own BdrvChild, however, for which
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+ * it could request permissions. Therefore we have to bypass the permission
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+ * system for the moment. */
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+ // assert(child->perm & (BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE));
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/* Cover entire cluster so no additional backing file I/O is required when
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* allocating cluster in the image file.
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--
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2.12.0
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