Re: explicit dcache <-> user-space cache coherency, sys_mark_dir_clean(), O_CLEAN

[Pavel Machek]

Hi!

> generation counters are problematic if they are not persistent. But
> there's a pretty natural persistent 'generation counter' which could be
> used for Samba's purpose: the mtime of the directory. The problem right
> now is that it doesnt have enough resolution to be a true unique
> generation counter. But having high-resolution mtime is a goal anyway.
> 
> XFS is one filesystem that has high-resolution mtime:
> 
>  typedef struct xfs_timestamp {
>          __int32_t       t_sec;          /* timestamp seconds */
>          __int32_t       t_nsec;         /* timestamp nanoseconds */
>  } xfs_timestamp_t;
> 
> monotonity is important: two successive directory operations to not be
> possible within the same nanosecond. This is not possible with current
> hardware - but how about future hardware? Can we make an assumption like
> this?

Does not ndelay(1) if samba notices mtime is too young in the samba code
fix that?
-- 
64 bytes from 195.113.31.123: icmp_seq=28 ttl=51 time=448769.1 ms         

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