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SubjectRe: fadvise syscall?
Jan Hudec wrote:

>>Followup to: <5.1.0.14.2.20020318000057.051d30e0@pop.cus.cam.ac.uk>
>>By author: Anton Altaparmakov <aia21@cam.ac.uk>
>>In newsgroup: linux.dev.fs.devel
>>
>>>Ok, so basically we want both fadvise() and open(2) semantics, with the
>>>open(2) being a superset of the fadvise() capabilities (some things no
>>>longer make sense to be specified once the file is open). They can of
>>>course both be calling the same common helpers inside the kernel...
>>>
>>If they're open() flags, they should probably be controlled with
>>fcntl() rather than with a new system call.
>>
>
>Then posix_fadvise interface can be implemented in libc using fcntl.
>
Indeed it can be... but it less flexible that way, unless you want to
add another level of indirection.

It is far better for future-proofing the interface IMO if fadvise is
implementing directly. Hints are less important than open O_xxx flags
or F_xxx flags, because an implementation can safely ignore 100% of the
fadvise hints, if it so chooses. One cannot say the same thing for
open/fcntl flags.

So, different class of fd flags deserves a different syscall, IMO...

Jeff






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