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| author | Zheng Yejian <zhengyejian1@huawei.com> | 2021-05-15 22:06:30 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2022-11-30 16:13:18 -0800 |
| commit | 457139f16ae15d86df1e491fc45a9ea56def57b5 (patch) | |
| tree | ee2b4f536355921a5a6dfbcdab9029e6ea6bfa69 | |
| parent | de985c109096b236d43e98da0c65376bf3bc24fb (diff) | |
| download | lwn-457139f16ae15d86df1e491fc45a9ea56def57b5.tar.gz lwn-457139f16ae15d86df1e491fc45a9ea56def57b5.zip | |
acct: fix accuracy loss for input value of encode_comp_t()
Patch series "Fix encode_comp_t()".
Type conversion in encode_comp_t() may look a bit problematic.
This patch (of 2):
See calculation of ac_{u,s}time in fill_ac():
> ac->ac_utime = encode_comp_t(nsec_to_AHZ(pacct->ac_utime));
> ac->ac_stime = encode_comp_t(nsec_to_AHZ(pacct->ac_stime));
Return value of nsec_to_AHZ() is always type of 'u64', but it is handled
as type of 'unsigned long' in encode_comp_t, and accuracy loss would
happen on 32-bit platform when 'unsigned long' value is 32-bit-width.
So 'u64' value of encode_comp_t() may look better.
Link: https://lkml.kernel.org/r/20210515140631.369106-1-zhengyejian1@huawei.com
Link: https://lkml.kernel.org/r/20210515140631.369106-2-zhengyejian1@huawei.com
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Randy Dunlap <rdunlap@infradead.org> # build-tested
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zhang Jinhao <zhangjinhao2@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | kernel/acct.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/acct.c b/kernel/acct.c index 62200d799b9b..31b09cf7189c 100644 --- a/kernel/acct.c +++ b/kernel/acct.c @@ -320,7 +320,7 @@ void acct_exit_ns(struct pid_namespace *ns) } /* - * encode an unsigned long into a comp_t + * encode an u64 into a comp_t * * This routine has been adopted from the encode_comp_t() function in * the kern_acct.c file of the FreeBSD operating system. The encoding @@ -331,7 +331,7 @@ void acct_exit_ns(struct pid_namespace *ns) #define EXPSIZE 3 /* Base 8 (3 bit) exponent. */ #define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */ -static comp_t encode_comp_t(unsigned long value) +static comp_t encode_comp_t(u64 value) { int exp, rnd; |