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| author | Mike Snitzer <snitzer@redhat.com> | 2013-08-20 15:05:17 -0400 |
|---|---|---|
| committer | Chanho Park <chanho61.park@samsung.com> | 2014-03-20 17:43:57 +0900 |
| commit | 27ef0a9763eeacc639aeccb610a8cc8596412f4b (patch) | |
| tree | 1fa11387d0300efe15c129a880ce0f2880fc3896 /lib | |
| parent | 75b4dccedb252c8160a3eb606979cc4f55012a08 (diff) | |
| download | linux-3.10-27ef0a9763eeacc639aeccb610a8cc8596412f4b.tar.gz linux-3.10-27ef0a9763eeacc639aeccb610a8cc8596412f4b.tar.bz2 linux-3.10-27ef0a9763eeacc639aeccb610a8cc8596412f4b.zip | |
math64: New separate div64_u64_rem helper
Commit f792685006274a850e6cc0ea9ade275ccdfc90bc ("math64: New
div64_u64_rem helper") implemented div64_u64 in terms of div64_u64_rem.
But div64_u64_rem was removed because it slowed down div64_u64 (and
there were no other users of div64_u64_rem).
Device Mapper's I/O statistics support has a need for div64_u64_rem;
reintroduce this helper as a separate method that doesn't slow down
div64_u64, especially on 32-bit systems.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
[backport]
Signed-off-by: Maciej Wereski <m.wereski@partner.samsung.com>
Change-Id: Icd721ff57c6d127e7acb0bf17d233d0a50ff24da
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/div64.c | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/lib/div64.c b/lib/div64.c index a163b6caef7..4382ad77777 100644 --- a/lib/div64.c +++ b/lib/div64.c @@ -79,6 +79,46 @@ EXPORT_SYMBOL(div_s64_rem); #endif /** + * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder + * @dividend: 64bit dividend + * @divisor: 64bit divisor + * @remainder: 64bit remainder + * + * This implementation is a comparable to algorithm used by div64_u64. + * But this operation, which includes math for calculating the remainder, + * is kept distinct to avoid slowing down the div64_u64 operation on 32bit + * systems. + */ +#ifndef div64_u64_rem +u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) +{ + u32 high = divisor >> 32; + u64 quot; + + if (high == 0) { + u32 rem32; + quot = div_u64_rem(dividend, divisor, &rem32); + *remainder = rem32; + } else { + int n = 1 + fls(high); + quot = div_u64(dividend >> n, divisor >> n); + + if (quot != 0) + quot--; + + *remainder = dividend - quot * divisor; + if (*remainder >= divisor) { + quot++; + *remainder -= divisor; + } + } + + return quot; +} +EXPORT_SYMBOL(div64_u64_rem); +#endif + +/** * div64_u64 - unsigned 64bit divide with 64bit divisor * @dividend: 64bit dividend * @divisor: 64bit divisor |