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bcache: fix bch_hprint crash and improve output

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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>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Michael Lyle 2017-09-06 14:26:02 +08:00 committed by Jens Axboe
parent 7b6a8570e0
commit 9276717b9e
1 changed files with 31 additions and 11 deletions
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42
drivers/md/bcache/util.c
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@ -74,24 +74,44 @@ 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 < 0)
q = -v;
else
q = v;
if (v < 100 && v > -100)
snprintf(dec, sizeof(dec), ".%i", t / 100);
/* 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++;
return sprintf(buf, "%lli%s%c", v, dec, units[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[],