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    SubjectRe: [PATCH 3/9] rbd: avoid out-of-range warning
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    On 3/28/24 22:53, Alex Elder wrote:
    > On 3/28/24 9:30 AM, Arnd Bergmann wrote:
    >> From: Arnd Bergmann <arnd@arndb.de>
    >>
    >> clang-14 points out that the range check is always true on 64-bit
    >> architectures since a u32 is not greater than the allowed size:
    >>
    >> drivers/block/rbd.c:6079:17: error: result of comparison of constant
    >> 2305843009213693948 with expression of type 'u32' (aka 'unsigned
    >> int') is always false
    >> [-Werror,-Wtautological-constant-out-of-range-compare]
    > w
    >>              ~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    >>
    >> This is harmless, so just change the type of the temporary to size_t
    >> to shut up that warning.
    >
    > This fixes the warning, but then the now size_t value is passed
    > to ceph_decode_32_safe(), which implies a different type conversion.
    > That too is not harmful, but...
    >
    > Could we just cast the value in the comparison instead?
    >
    >   if ((size_t)snap_count > (SIZE_MAX - sizeof (struct ceph_snap_context))
    >
    > You could drop the space between sizeof and ( while
    > you're at it (I always used the space back then).
    >
    Agree.

    - Xiubo


    > -Alex
    >
    >>
    >> Fixes: bb23e37acb2a ("rbd: refactor rbd_header_from_disk()")
    >> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    >> ---
    >>   drivers/block/rbd.c | 2 +-
    >>   1 file changed, 1 insertion(+), 1 deletion(-)
    >>
    >> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
    >> index 26ff5cd2bf0a..cb25ee513ada 100644
    >> --- a/drivers/block/rbd.c
    >> +++ b/drivers/block/rbd.c
    >> @@ -6062,7 +6062,7 @@ static int rbd_dev_v2_snap_context(struct
    >> rbd_device *rbd_dev,
    >>       void *p;
    >>       void *end;
    >>       u64 seq;
    >> -    u32 snap_count;
    >> +    size_t snap_count;
    >>       struct ceph_snap_context *snapc;
    >>       u32 i;
    >
    >


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