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Message-ID: <20141113221139.GG2598@htj.dyndns.org>
Date: Thu, 13 Nov 2014 17:11:39 -0500
From: Tejun Heo <tj@...nel.org>
To: Jens Axboe <axboe@...nel.dk>,
Alexander Viro <viro@...iv.linux.org.uk>,
Christoph Hellwig <hch@...radead.org>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH vfs 2/2] {block|char}_dev: remove inode->i_devices
inode->i_devices is a list_head used to link device inodes to the
corresponding block_device or cdev. This patch makes block_device and
cdev usfe ptrset to keep track of the inodes instead of linking
inode->i_devices allowing removal of the field and thus reduction of
struct inode by two pointers.
The conversion is staright-forward. list_add() is replaced with
preloaded ptrset_add(), list_del_init() with ptrset_del(), and list
iteration with ptrset_for_each(). The only part which isn't direct
one-to-one mapping is the error handling after ptrset_add() failure.
The saved two pointers will be used by cgroup writback support.
Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Christoph Hellwig <hch@...radead.org>
---
fs/block_dev.c | 39 +++++++++++++++++++++++----------------
fs/char_dev.c | 25 +++++++++++++++----------
fs/inode.c | 1 -
include/linux/cdev.h | 4 ++--
include/linux/fs.h | 4 ++--
5 files changed, 42 insertions(+), 31 deletions(-)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -458,7 +458,7 @@ static void init_once(void *foo)
memset(bdev, 0, sizeof(*bdev));
mutex_init(&bdev->bd_mutex);
- INIT_LIST_HEAD(&bdev->bd_inodes);
+ ptrset_init(&bdev->bd_inodes);
INIT_LIST_HEAD(&bdev->bd_list);
#ifdef CONFIG_SYSFS
INIT_LIST_HEAD(&bdev->bd_holder_disks);
@@ -470,7 +470,7 @@ static void init_once(void *foo)
static inline void __bd_forget(struct inode *inode)
{
- list_del_init(&inode->i_devices);
+ ptrset_del(inode, &inode->i_bdev->bd_inodes);
inode->i_bdev = NULL;
inode->i_mapping = &inode->i_data;
}
@@ -478,14 +478,15 @@ static inline void __bd_forget(struct in
static void bdev_evict_inode(struct inode *inode)
{
struct block_device *bdev = &BDEV_I(inode)->bdev;
- struct list_head *p;
+ struct ptrset_iter iter;
+ struct inode *bd_inode;
+
truncate_inode_pages_final(&inode->i_data);
invalidate_inode_buffers(inode); /* is it needed here? */
clear_inode(inode);
spin_lock(&bdev_lock);
- while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) {
- __bd_forget(list_entry(p, struct inode, i_devices));
- }
+ ptrset_for_each(bd_inode, &bdev->bd_inodes, &iter)
+ __bd_forget(bd_inode);
list_del_init(&bdev->bd_list);
spin_unlock(&bdev_lock);
}
@@ -634,20 +635,26 @@ static struct block_device *bd_acquire(s
bdev = bdget(inode->i_rdev);
if (bdev) {
+ ptrset_preload(GFP_KERNEL);
spin_lock(&bdev_lock);
if (!inode->i_bdev) {
- /*
- * We take an additional reference to bd_inode,
- * and it's released in clear_inode() of inode.
- * So, we can access it via ->i_mapping always
- * without igrab().
- */
- ihold(bdev->bd_inode);
- inode->i_bdev = bdev;
- inode->i_mapping = bdev->bd_inode->i_mapping;
- list_add(&inode->i_devices, &bdev->bd_inodes);
+ if (!ptrset_add(inode, &bdev->bd_inodes, GFP_NOWAIT)) {
+ /*
+ * We take an additional reference to bd_inode,
+ * and it's released in clear_inode() of inode.
+ * So, we can access it via ->i_mapping always
+ * without igrab().
+ */
+ ihold(bdev->bd_inode);
+ inode->i_bdev = bdev;
+ inode->i_mapping = bdev->bd_inode->i_mapping;
+ } else {
+ bdput(bdev);
+ bdev = NULL;
+ }
}
spin_unlock(&bdev_lock);
+ ptrset_preload_end();
}
return bdev;
}
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -383,16 +383,20 @@ static int chrdev_open(struct inode *ino
if (!kobj)
return -ENXIO;
new = container_of(kobj, struct cdev, kobj);
+ ptrset_preload(GFP_KERNEL);
spin_lock(&cdev_lock);
/* Check i_cdev again in case somebody beat us to it while
we dropped the lock. */
p = inode->i_cdev;
if (!p) {
- inode->i_cdev = p = new;
- list_add(&inode->i_devices, &p->list);
- new = NULL;
+ ret = ptrset_add(inode, &new->inodes, GFP_NOWAIT);
+ if (!ret) {
+ inode->i_cdev = p = new;
+ new = NULL;
+ }
} else if (!cdev_get(p))
ret = -ENXIO;
+ ptrset_preload_end();
} else if (!cdev_get(p))
ret = -ENXIO;
spin_unlock(&cdev_lock);
@@ -422,18 +426,19 @@ static int chrdev_open(struct inode *ino
void cd_forget(struct inode *inode)
{
spin_lock(&cdev_lock);
- list_del_init(&inode->i_devices);
+ ptrset_del(inode, &inode->i_cdev->inodes);
inode->i_cdev = NULL;
spin_unlock(&cdev_lock);
}
static void cdev_purge(struct cdev *cdev)
{
+ struct inode *inode;
+ struct ptrset_iter iter;
+
spin_lock(&cdev_lock);
- while (!list_empty(&cdev->list)) {
- struct inode *inode;
- inode = container_of(cdev->list.next, struct inode, i_devices);
- list_del_init(&inode->i_devices);
+ ptrset_for_each(inode, &cdev->inodes, &iter) {
+ ptrset_del(inode, &cdev->inodes);
inode->i_cdev = NULL;
}
spin_unlock(&cdev_lock);
@@ -543,7 +548,7 @@ struct cdev *cdev_alloc(void)
{
struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
if (p) {
- INIT_LIST_HEAD(&p->list);
+ ptrset_init(&p->inodes);
kobject_init(&p->kobj, &ktype_cdev_dynamic);
}
return p;
@@ -560,7 +565,7 @@ struct cdev *cdev_alloc(void)
void cdev_init(struct cdev *cdev, const struct file_operations *fops)
{
memset(cdev, 0, sizeof *cdev);
- INIT_LIST_HEAD(&cdev->list);
+ ptrset_init(&cdev->inodes);
kobject_init(&cdev->kobj, &ktype_cdev_default);
cdev->ops = fops;
}
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -366,7 +366,6 @@ void inode_init_once(struct inode *inode
{
memset(inode, 0, sizeof(*inode));
INIT_HLIST_NODE(&inode->i_hash);
- INIT_LIST_HEAD(&inode->i_devices);
INIT_LIST_HEAD(&inode->i_wb_list);
INIT_LIST_HEAD(&inode->i_lru);
address_space_init_once(&inode->i_data);
--- a/include/linux/cdev.h
+++ b/include/linux/cdev.h
@@ -3,7 +3,7 @@
#include <linux/kobject.h>
#include <linux/kdev_t.h>
-#include <linux/list.h>
+#include <linux/ptrset.h>
struct file_operations;
struct inode;
@@ -13,7 +13,7 @@ struct cdev {
struct kobject kobj;
struct module *owner;
const struct file_operations *ops;
- struct list_head list;
+ struct ptrset inodes;
dev_t dev;
unsigned int count;
};
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -28,6 +28,7 @@
#include <linux/uidgid.h>
#include <linux/lockdep.h>
#include <linux/percpu-rwsem.h>
+#include <linux/ptrset.h>
#include <linux/blk_types.h>
#include <asm/byteorder.h>
@@ -426,7 +427,7 @@ struct block_device {
struct inode * bd_inode; /* will die */
struct super_block * bd_super;
struct mutex bd_mutex; /* open/close mutex */
- struct list_head bd_inodes;
+ struct ptrset bd_inodes;
void * bd_claiming;
void * bd_holder;
int bd_holders;
@@ -609,7 +610,6 @@ struct inode {
#ifdef CONFIG_QUOTA
struct dquot *i_dquot[MAXQUOTAS];
#endif
- struct list_head i_devices;
union {
struct pipe_inode_info *i_pipe;
struct block_device *i_bdev;
--
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