fs: Remove i_cindex from struct inode
Theodore Ts'o [Thu, 21 May 2009 20:01:00 +0000 (16:01 -0400)]
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>

drivers/ieee1394/dv1394.c
drivers/ieee1394/ieee1394_core.h
fs/char_dev.c
include/linux/cdev.h
include/linux/fs.h

index 823a629..2cd00b5 100644 (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;
                }
 
index 21d50f7..28b9f58 100644 (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;
index 38f7122..b7c9d51 100644 (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);
index fb45919..f389e31 100644 (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;
index e7833ef..bcd6370 100644 (file)
@@ -751,7 +751,6 @@ struct inode {
                struct block_device     *i_bdev;
                struct cdev             *i_cdev;
        };
-       int                     i_cindex;
 
        __u32                   i_generation;