Libguestfs - Jan 2022 - [v2v PATCH 2/2] lib/utils: get_disk_allocated: adopt the int64 element type for "entries"

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2027598

This small series (esp. the second patch) is necessary in virt-v2v, for
putting the just-posted libnbd patch

  [Libguestfs] [libnbd PATCH] ocaml: map C's uint32_t to OCaml's int64
  https://listman.redhat.com/archives/libguestfs/2022-January/msg00093.html
  Message-Id: <20220114133833.24835-1-lersek at redhat.com>

to use.

Thanks,
Laszlo

Laszlo Ersek (2):
  lib/utils: get_disk_allocated: assert that NBD block length is
    positive
  lib/utils: get_disk_allocated: adopt the int64 element type for
    "entries"

 lib/utils.ml | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)


base-commit: 4578887821d8c70190f5f8c3edf4779f1d502d06
-- 
2.19.1.3.g30247aa5d201

It makes no sense for the NBD server to return a zero-length block, plus
it used to be a bug in the libnbd OCaml bindings to wrap 32-bit block
lengths with the MSB set around to negative (signed) 32-bit integers
(which would then be widened to negative (signed) 64-bit integers).

Any non-positive "len" value breaks the progression of
"fetch_offset",
potentially leading to an infinite loop.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2027598
Signed-off-by: Laszlo Ersek <lersek at redhat.com>
---
 lib/utils.ml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/utils.ml b/lib/utils.ml
index 4c43a4b5161d..f599b0e32450 100644
--- a/lib/utils.ml
+++ b/lib/utils.ml
@@ -197,6 +197,7 @@ let get_disk_allocated ~dir ~disknr                    for i
= 0 to Array.length entries / 2 - 1 do
                     let len = Int64.of_int32 entries.(i * 2)
                     and typ = entries.(i * 2 + 1) in
+                    assert (len > 0_L);
                     if Int32.logand typ 1_l = 0_l then
                       allocated := !allocated +^ len;
                     fetch_offset := !fetch_offset +^ len
-- 
2.19.1.3.g30247aa5d201

Adapt our "Utils.get_disk_allocated" function to the changed signature
of
"NBD.block_status", coming from libnbd patch

  ocaml: map C's uint32_t to OCaml's int64

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2027598
Signed-off-by: Laszlo Ersek <lersek at redhat.com>
---
 lib/utils.ml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/utils.ml b/lib/utils.ml
index f599b0e32450..4c8998c28a3c 100644
--- a/lib/utils.ml
+++ b/lib/utils.ml
@@ -195,10 +195,10 @@ let get_disk_allocated ~dir ~disknr                 (fun
ctx offset entries err ->
                   assert (ctx = alloc_ctx);
                   for i = 0 to Array.length entries / 2 - 1 do
-                    let len = Int64.of_int32 entries.(i * 2)
+                    let len = entries.(i * 2)
                     and typ = entries.(i * 2 + 1) in
                     assert (len > 0_L);
-                    if Int32.logand typ 1_l = 0_l then
+                    if typ &^ 1_L = 0_L then
                       allocated := !allocated +^ len;
                     fetch_offset := !fetch_offset +^ len
                   done;
-- 
2.19.1.3.g30247aa5d201

On 01/14/22 14:50, Laszlo Ersek wrote:
> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2027598
> 
> This small series (esp. the second patch) is necessary in virt-v2v, for
> putting the just-posted libnbd patch
> 
>   [Libguestfs] [libnbd PATCH] ocaml: map C's uint32_t to OCaml's
int64
>   https://listman.redhat.com/archives/libguestfs/2022-January/msg00093.html
>   Message-Id: <20220114133833.24835-1-lersek at redhat.com>
> 
> to use.
> 
> Thanks,
> Laszlo
> 
> Laszlo Ersek (2):
>   lib/utils: get_disk_allocated: assert that NBD block length is
>     positive
>   lib/utils: get_disk_allocated: adopt the int64 element type for
>     "entries"
> 
>  lib/utils.ml | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> 
> base-commit: 4578887821d8c70190f5f8c3edf4779f1d502d06
> 
Commit range 4578887821d8..a2afed32d8b1.

Thanks!
Laszlo