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authorHanna Czenczek <hreitz@redhat.com>2023-02-27 11:47:24 +0100
committerKevin Wolf <kwolf@redhat.com>2023-03-10 15:14:46 +0100
commit1703eb1c27a6010ff33d5add2d76aadc9b2777bd (patch)
treeacd0f4c0d0842e9c8b9288687a037b27de529e1b /docs/sphinx/kerneldoc.py
parentee59483267de29056b5b2ee2421ef3844e5c9932 (diff)
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block/fuse: Let PUNCH_HOLE write zeroes
fallocate(2) says about PUNCH_HOLE: "After a successful call, subsequent
reads from this range will return zeros."  As it is, PUNCH_HOLE is
implemented as a call to blk_pdiscard(), which does not guarantee this.

We must call blk_pwrite_zeroes() instead.  The difference to ZERO_RANGE
is that we pass the `BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK` flags to
the call -- the storage is supposed to be unmapped, and a slow fallback
by actually writing zeroes as data is not allowed.

Closes: https://gitlab.com/qemu-project/qemu/-/issues/1507
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-Id: <20230227104725.33511-2-hreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'docs/sphinx/kerneldoc.py')
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