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fs: Remove i_cindex from struct inode

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The only user of the i_cindex element in the inode structure is used
is by the firewire drivers.  As part of an attempt to slim down the
inode structure to save memory --- since a typical Linux system will
have hundreds of thousands if not millions of inodes cached, a
reduction in the size inode has high leverage.

The firewire driver does not need i_cindex in any fast path, so it's
simple enough to calculate when it is needed, instead of wasting space
in the inode structure.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: krh@redhat.com
Cc: stefanr@s5r6.in-berlin.de
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Theodore Ts'o 2009-05-21 16:01:00 -04:00 committed by Al Viro
parent ebc1ac1645
commit 9fd5746fd3
5 changed files with 23 additions and 5 deletions
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5
drivers/ieee1394/dv1394.c
View file

@ -1789,12 +1789,13 @@ static int dv1394_open(struct inode *inode, struct file *file)
} else {
/* look up the card by ID */
unsigned long flags;
int idx = ieee1394_file_to_instance(file);
spin_lock_irqsave(&dv1394_cards_lock, flags);
if (!list_empty(&dv1394_cards)) {
struct video_card *p;
list_for_each_entry(p, &dv1394_cards, list) {
if ((p->id) == ieee1394_file_to_instance(file)) {
if ((p->id) == idx) {
video = p;
break;
}
@ -1803,7 +1804,7 @@ static int dv1394_open(struct inode *inode, struct file *file)
spin_unlock_irqrestore(&dv1394_cards_lock, flags);
if (!video) {
debug_printk("dv1394: OHCI card %d not found", ieee1394_file_to_instance(file));
debug_printk("dv1394: OHCI card %d not found", idx);
return -ENODEV;
}

6
drivers/ieee1394/ieee1394_core.h
View file

@ -5,6 +5,7 @@
#include <linux/fs.h>
#include <linux/list.h>
#include <linux/types.h>
#include <linux/cdev.h>
#include <asm/atomic.h>
#include "hosts.h"
@ -155,7 +156,10 @@ void hpsb_packet_received(struct hpsb_host *host, quadlet_t *data, size_t size,
*/
static inline unsigned char ieee1394_file_to_instance(struct file *file)
{
return file->f_path.dentry->d_inode->i_cindex;
int idx = cdev_index(file->f_path.dentry->d_inode);
if (idx < 0)
idx = 0;
return idx;
}
extern int hpsb_disable_irm;

14
fs/char_dev.c
View file

@ -375,7 +375,6 @@ static int chrdev_open(struct inode *inode, struct file *filp)
p = inode->i_cdev;
if (!p) {
inode->i_cdev = p = new;
inode->i_cindex = idx;
list_add(&inode->i_devices, &p->list);
new = NULL;
} else if (!cdev_get(p))
@ -405,6 +404,18 @@ static int chrdev_open(struct inode *inode, struct file *filp)
return ret;
}
int cdev_index(struct inode *inode)
{
int idx;
struct kobject *kobj;
kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
if (!kobj)
return -1;
kobject_put(kobj);
return idx;
}
void cd_forget(struct inode *inode)
{
spin_lock(&cdev_lock);
@ -557,6 +568,7 @@ EXPORT_SYMBOL(cdev_init);
EXPORT_SYMBOL(cdev_alloc);
EXPORT_SYMBOL(cdev_del);
EXPORT_SYMBOL(cdev_add);
EXPORT_SYMBOL(cdev_index);
EXPORT_SYMBOL(register_chrdev);
EXPORT_SYMBOL(unregister_chrdev);
EXPORT_SYMBOL(directly_mappable_cdev_bdi);

2
include/linux/cdev.h
View file

@ -28,6 +28,8 @@ int cdev_add(struct cdev *, dev_t, unsigned);
void cdev_del(struct cdev *);
int cdev_index(struct inode *inode);
void cd_forget(struct inode *);
extern struct backing_dev_info directly_mappable_cdev_bdi;

1
include/linux/fs.h
View file

@ -751,7 +751,6 @@ struct inode {
struct block_device *i_bdev;
struct cdev *i_cdev;
};
int i_cindex;
__u32 i_generation;