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Date: Thu, 21 May 2009 16:01:00 -0400
From: Theodore Ts'o <tytso@....edu>
To: linux-kernel@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
krh@...hat.com, stefanr@...6.in-berlin.de
Subject: [PATCH 2/5] fs: Remove i_cindex from struct inode
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@....edu>
Cc: krh@...hat.com
Cc: stefanr@...6.in-berlin.de
Cc: linux-fsdevel@...r.kernel.org
---
drivers/ieee1394/dv1394.c | 5 +++--
drivers/ieee1394/ieee1394_core.h | 5 ++++-
fs/char_dev.c | 14 +++++++++++++-
include/linux/cdev.h | 2 ++
include/linux/fs.h | 1 -
5 files changed, 22 insertions(+), 5 deletions(-)
diff --git a/drivers/ieee1394/dv1394.c b/drivers/ieee1394/dv1394.c
index 823a629..2cd00b5 100644
--- a/drivers/ieee1394/dv1394.c
+++ b/drivers/ieee1394/dv1394.c
@@ -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;
}
diff --git a/drivers/ieee1394/ieee1394_core.h b/drivers/ieee1394/ieee1394_core.h
index 21d50f7..fda0f5e 100644
--- a/drivers/ieee1394/ieee1394_core.h
+++ b/drivers/ieee1394/ieee1394_core.h
@@ -155,7 +155,10 @@ 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;
diff --git a/fs/char_dev.c b/fs/char_dev.c
index 38f7122..b7c9d51 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -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);
diff --git a/include/linux/cdev.h b/include/linux/cdev.h
index fb45919..f389e31 100644
--- a/include/linux/cdev.h
+++ b/include/linux/cdev.h
@@ -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;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9b20f13..e3b8334 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -751,7 +751,6 @@ struct inode {
struct block_device *i_bdev;
struct cdev *i_cdev;
};
- int i_cindex;
__u32 i_generation;
--
1.6.3.1.1.g75fc.dirty
--
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