Re: [PATCH] FILESYSTEMS: Delete unused "int dummy[5]" from inodes_stat_t.

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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
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