On 5/29/07, Randy Dunlap <[email protected]> wrote:
Robert P. J. Day wrote:
> On Tue, 29 May 2007, Randy Dunlap wrote:
>
>> On Tue, 29 May 2007 14:07:01 -0400 (EDT) Robert P. J. Day wrote:
>>
>>> On Tue, 29 May 2007, Andrew Morton wrote:
>>>
>>>> kernel/sysctl.c:
>>>>
>>>> {
>>>> .ctl_name = FS_STATINODE,
>>>> .procname = "inode-state",
>>>> .data = &inodes_stat,
>>>> .maxlen = 7*sizeof(int), <-----
>>>> .mode = 0444,
>>>> .proc_handler = &proc_dointvec,
>>>> },
>>>>
>>>> akpm:/home/akpm> cat /proc/sys/fs/inode-state
>>>> 608039 178454 0 0 0 0 0
>>>>
>>>> So it _is_ used: to present those five zeroes. I think this is
>>>> for back-compatibility with some cretaceous-era kernel.
>>> ah, gotcha. well, i'll leave this up to someone else to do
>>> anything with if they are so inclined.
>> There's little to be done, except possibly put a /* comment */ on
>> the struct's dummy line so that we don't go thru this again in N
>> years.
>
> so, just to clarify, what *is* the value of those trailing five
> zeroes? andrew suggests it's to be backward-compatible with an old
> kernel, which doesn't make much sense to me. it would make more sense
> to say that that's backward-compatible with some old userspace app
> that always wants to see seven values and just ignores the last five.
Agreed, it's for compat with some (unknown) userspace app that reads
/proc/sys/fs/inode-state and scans for 7 (or more than 2) numbers there.
The mantra is "don't break userspace," so we leave the numbers there...
Couldn't you remove the dummy member and just have the proc entry
print out 5 dummy zeros?
josh
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