On 17.11.2016 15:55, Paul Menzel wrote:
Dear Linux folks,
On 11/16/16 22:24, Donald Buczek wrote:
The relevant commit is 703b5fa which includes
The commit message summary is *fs/dcache.c: Save one 32-bit multiply
in dcache lookup*.
static inline unsigned long end_name_hash(unsigned long hash)
{
- return (unsigned int)hash;
+ return __hash_32((unsigned int)hash);
}
__hash_32 is a multiplication by 0x61C88647 ( hash.h )
And this exactly is the difference between the hash value of "host0" on
the 4.4 and the 4.8 system:
DB<2> x sprintf '%x',0x11bf1ddd*0x61C88647
0 '6c750ef074af64b'
The bug, of course, is in the userspace tool tw_cli which wrongly
assumes that the names would be returned in the "right" order by
getdents.
Nice analysis.
Unfortunately, I don’t find the discussion of the patch on the Linux
kernel mailing list.
703b5fa sits on top of 8387ff2 from Linus Torvalds. Maybe he didn't send
his own suggestion to the lists but to the three people named in that
commit only. Maybe George Spelvin replied with his patch as an
improvement and Linus just accepted it on his own branch and merged
(554828e).
Donald
--
Donald Buczek
buczek@xxxxxxxxxxxxx
Tel: +49 30 8413 1433
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