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    Subject[PATCH 5.3 085/112] btrfs: fix balance convert to single on 32-bit host CPUs
    Date
    From: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>

    commit 7a54789074a54f64addf5b49bf1994f478337a83 upstream.

    Currently, the command:

    btrfs balance start -dconvert=single,soft .

    on a Raspberry Pi produces the following kernel message:

    BTRFS error (device mmcblk0p2): balance: invalid convert data profile single

    This fails because we use is_power_of_2(unsigned long) to validate
    the new data profile, the constant for 'single' profile uses bit 48,
    and there are only 32 bits in a long on ARM.

    Fix by open-coding the check using u64 variables.

    Tested by completing the original balance command on several Raspberry
    Pis.

    Fixes: 818255feece6 ("btrfs: use common helper instead of open coding a bit test")
    CC: stable@vger.kernel.org # 4.20+
    Signed-off-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
    Reviewed-by: David Sterba <dsterba@suse.com>
    Signed-off-by: David Sterba <dsterba@suse.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/btrfs/volumes.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    --- a/fs/btrfs/volumes.c
    +++ b/fs/btrfs/volumes.c
    @@ -3854,7 +3854,11 @@ static int alloc_profile_is_valid(u64 fl
    return !extended; /* "0" is valid for usual profiles */

    /* true if exactly one bit set */
    - return is_power_of_2(flags);
    + /*
    + * Don't use is_power_of_2(unsigned long) because it won't work
    + * for the single profile (1ULL << 48) on 32-bit CPUs.
    + */
    + return flags != 0 && (flags & (flags - 1)) == 0;
    }

    static inline int balance_need_close(struct btrfs_fs_info *fs_info)

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