[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <465C71EA.5040706@oracle.com>
Date: Tue, 29 May 2007 11:33:14 -0700
From: Randy Dunlap <randy.dunlap@...cle.com>
To: "Robert P. J. Day" <rpjday@...dspring.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] FILESYSTEMS: Delete unused "int dummy[5]" from inodes_stat_t.
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...
> in any event, from Documentation/filesystems/proc.txt:
>
> "inode-state contains two actual numbers and five dummy values. The
> numbers are nr_inodes and nr_free_inodes (in order of appearance)."
>
> if even the documentation calls them dummy values, do they really have
> any residual value at this point? and on that note, i'll stop harping
> on this and move on.
>
> rday
--
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists