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    Subject[PATCH 3.16 104/133] bcache: fix bch_hprint crash and improve output
    3.16.51-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Michael Lyle <mlyle@lyle.org>

    commit 9276717b9e297a62d1151a43d1cd286213f68eb7 upstream.

    Most importantly, solve a crash where %llu was used to format signed
    numbers. This would cause a buffer overflow when reading sysfs
    writeback_rate_debug, as only 20 bytes were allocated for this and
    %llu writes 20 characters plus a null.

    Always use the units mechanism rather than having different output
    paths for simplicity.

    Also, correct problems with display output where 1.10 was a larger
    number than 1.09, by multiplying by 10 and then dividing by 1024 instead
    of dividing by 100. (Remainders of >= 1000 would print as .10).

    Minor changes: Always display the decimal point instead of trying to
    omit it based on number of digits shown. Decide what units to use
    based on 1000 as a threshold, not 1024 (in other words, always print
    at most 3 digits before the decimal point).

    Signed-off-by: Michael Lyle <mlyle@lyle.org>
    Reported-by: Dmitry Yu Okunev <dyokunev@ut.mephi.ru>
    Acked-by: Kent Overstreet <kent.overstreet@gmail.com>
    Reviewed-by: Coly Li <colyli@suse.de>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/md/bcache/util.c | 50 +++++++++++++++++++++++++++++++++---------------
    1 file changed, 35 insertions(+), 15 deletions(-)

    --- a/drivers/md/bcache/util.c
    +++ b/drivers/md/bcache/util.c
    @@ -73,24 +73,44 @@ STRTO_H(strtouint, unsigned int)
    STRTO_H(strtoll, long long)
    STRTO_H(strtoull, unsigned long long)

    +/**
    + * bch_hprint() - formats @v to human readable string for sysfs.
    + *
    + * @v - signed 64 bit integer
    + * @buf - the (at least 8 byte) buffer to format the result into.
    + *
    + * Returns the number of bytes used by format.
    + */
    ssize_t bch_hprint(char *buf, int64_t v)
    {
    static const char units[] = "?kMGTPEZY";
    - char dec[4] = "";
    - int u, t = 0;
    + int u = 0, t;

    - for (u = 0; v >= 1024 || v <= -1024; u++) {
    - t = v & ~(~0 << 10);
    - v >>= 10;
    - }
    + uint64_t q;

    - if (!u)
    - return sprintf(buf, "%llu", v);
    -
    - if (v < 100 && v > -100)
    - snprintf(dec, sizeof(dec), ".%i", t / 100);
    -
    - return sprintf(buf, "%lli%s%c", v, dec, units[u]);
    + if (v < 0)
    + q = -v;
    + else
    + q = v;
    +
    + /* For as long as the number is more than 3 digits, but at least
    + * once, shift right / divide by 1024. Keep the remainder for
    + * a digit after the decimal point.
    + */
    + do {
    + u++;
    +
    + t = q & ~(~0 << 10);
    + q >>= 10;
    + } while (q >= 1000);
    +
    + if (v < 0)
    + /* '-', up to 3 digits, '.', 1 digit, 1 character, null;
    + * yields 8 bytes.
    + */
    + return sprintf(buf, "-%llu.%i%c", q, t * 10 / 1024, units[u]);
    + else
    + return sprintf(buf, "%llu.%i%c", q, t * 10 / 1024, units[u]);
    }

    ssize_t bch_snprint_string_list(char *buf, size_t size, const char * const list[],
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