proc: decouple proc from VFS with "struct proc_ops"

Currently core /proc code uses "struct file_operations" for custom hooks,
however, VFS doesn't directly call them.  Every time VFS expands
file_operations hook set, /proc code bloats for no reason.

Introduce "struct proc_ops" which contains only those hooks which /proc
allows to call into (open, release, read, write, ioctl, mmap, poll).  It
doesn't contain module pointer as well.

Save ~184 bytes per usage:

	add/remove: 26/26 grow/shrink: 1/4 up/down: 1922/-6674 (-4752)
	Function                                     old     new   delta
	sysvipc_proc_ops                               -      72     +72
				...
	config_gz_proc_ops                             -      72     +72
	proc_get_inode                               289     339     +50
	proc_reg_get_unmapped_area                   110     107      -3
	close_pdeo                                   227     224      -3
	proc_reg_open                                289     284      -5
	proc_create_data                              60      53      -7
	rt_cpu_seq_fops                              256       -    -256
				...
	default_affinity_proc_fops                   256       -    -256
	Total: Before=5430095, After=5425343, chg -0.09%

Link: http://lkml.kernel.org/r/20191225172228.GA13378@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 0f3b557c9b77..41587276798e 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -39,7 +39,10 @@ struct proc_dir_entry {
 	spinlock_t pde_unload_lock;
 	struct completion *pde_unload_completion;
 	const struct inode_operations *proc_iops;
-	const struct file_operations *proc_fops;
+	union {
+		const struct proc_ops *proc_ops;
+		const struct file_operations *proc_dir_ops;
+	};
 	const struct dentry_operations *proc_dops;
 	union {
 		const struct seq_operations *seq_ops;