Date: Sat, 22 Sep 2001 01:54:10 -0400 (EDT)
From: Alexander Viro <viro@math.psu.edu>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Andrea Arcangeli <andrea@suse.de>
Subject: [PATCH] (1/6) further block_device cleanups
In-Reply-To: <20010922062525.O11674@athlon.random>
Message-ID: <Pine.GSO.4.21.0109220140390.11204-100000@weyl.math.psu.edu>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
OK, folks. Since it seems to survive the local beating (FWIW),
here is the beginning of sequence. I'll send the first 6 patches -
see yourself how much you want to apply on the first stage.
Part 1:
inodes with given ->i_bdev are sitting on a cyclic list,
anchored in bdev->bd_inodes and going through inode->i_devices.
bd_acquire(inode) either bumps refcount on ->i_bdev or sets
->i_bdev (grabbing block_device).
bd_forget(inode) takes inode from the list and resets ->i_bdev.
Called when we free inode.
if bdput(bdev) decides to free block_device (->bd_count hits 0)
it goes through the list (if non-empty) and removes all inodes from it,
resetting their ->i_bdev as it goes.
bd_acquire() is used in fs/devices.c and devfs instead of
setting ->i_bdev.
Now we can start surrounding the areas where we need ->i_bdev
with bd_acquire()/bdput(). Once it's done we can drop bd_acquire()
from init_special_inode() and bdput() from freeing inode, thus reducing
the lifetime of block_device to the time it spends actually used. That's
what will happen in next several chunks.
diff -urN S10-pre13-new/fs/block_dev.c S10-pre13-current/fs/block_dev.c
--- S10-pre13-new/fs/block_dev.c Fri Sep 21 16:31:16 2001
+++ S10-pre13-current/fs/block_dev.c Fri Sep 21 18:44:01 2001
@@ -437,6 +437,7 @@
{
memset(bdev, 0, sizeof(*bdev));
sema_init(&bdev->bd_sem, 1);
+ INIT_LIST_HEAD(&bdev->bd_inodes);
}
}
@@ -522,16 +523,57 @@
void bdput(struct block_device *bdev)
{
- if (atomic_dec_and_test(&bdev->bd_count)) {
+ if (atomic_dec_and_lock(&bdev->bd_count, &bdev_lock)) {
+ struct list_head *p;
if (bdev->bd_openers)
BUG();
if (bdev->bd_cache_openers)
BUG();
- spin_lock(&bdev_lock);
list_del(&bdev->bd_hash);
+ while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) {
+ struct inode *inode;
+ inode = list_entry(p, struct inode, i_devices);
+ list_del_init(p);
+ inode->i_bdev = NULL;
+ }
spin_unlock(&bdev_lock);
destroy_bdev(bdev);
}
+}
+
+int bd_acquire(struct inode *inode)
+{
+ struct block_device *bdev;
+ spin_lock(&bdev_lock);
+ if (inode->i_bdev) {
+ atomic_inc(&inode->i_bdev->bd_count);
+ spin_unlock(&bdev_lock);
+ return 0;
+ }
+ spin_unlock(&bdev_lock);
+ bdev = bdget(kdev_t_to_nr(inode->i_rdev));
+ if (!bdev)
+ return -ENOMEM;
+ spin_lock(&bdev_lock);
+ if (!inode->i_bdev) {
+ inode->i_bdev = bdev;
+ list_add(&inode->i_devices, &bdev->bd_inodes);
+ } else if (inode->i_bdev != bdev)
+ BUG();
+ spin_unlock(&bdev_lock);
+ return 0;
+}
+
+/* Call when you free inode */
+
+void bd_forget(struct inode *inode)
+{
+ spin_lock(&bdev_lock);
+ if (inode->i_bdev) {
+ list_del_init(&inode->i_devices);
+ inode->i_bdev = NULL;
+ }
+ spin_unlock(&bdev_lock);
}
static struct {
diff -urN S10-pre13-new/fs/devfs/base.c S10-pre13-current/fs/devfs/base.c
--- S10-pre13-new/fs/devfs/base.c Fri Sep 21 16:31:16 2001
+++ S10-pre13-current/fs/devfs/base.c Fri Sep 21 18:45:02 2001
@@ -2351,9 +2351,7 @@
{
inode->i_rdev = MKDEV (de->u.fcb.u.device.major,
de->u.fcb.u.device.minor);
- inode->i_bdev = bdget ( kdev_t_to_nr (inode->i_rdev) );
- inode->i_mapping->a_ops = &def_blk_aops;
- if (inode->i_bdev)
+ if (bd_acquire(inode) == 0)
{
if (!inode->i_bdev->bd_op && de->u.fcb.ops)
inode->i_bdev->bd_op = de->u.fcb.ops;
diff -urN S10-pre13-new/fs/devices.c S10-pre13-current/fs/devices.c
--- S10-pre13-new/fs/devices.c Thu May 24 18:26:44 2001
+++ S10-pre13-current/fs/devices.c Fri Sep 21 18:44:01 2001
@@ -207,7 +207,7 @@
} else if (S_ISBLK(mode)) {
inode->i_fop = &def_blk_fops;
inode->i_rdev = to_kdev_t(rdev);
- inode->i_bdev = bdget(rdev);
+ bd_acquire(inode);
} else if (S_ISFIFO(mode))
inode->i_fop = &def_fifo_fops;
else if (S_ISSOCK(mode))
diff -urN S10-pre13-new/fs/inode.c S10-pre13-current/fs/inode.c
--- S10-pre13-new/fs/inode.c Fri Sep 21 09:45:26 2001
+++ S10-pre13-current/fs/inode.c Fri Sep 21 18:44:01 2001
@@ -106,6 +106,7 @@
INIT_LIST_HEAD(&inode->i_dentry);
INIT_LIST_HEAD(&inode->i_dirty_buffers);
INIT_LIST_HEAD(&inode->i_dirty_data_buffers);
+ INIT_LIST_HEAD(&inode->i_devices);
sema_init(&inode->i_sem, 1);
sema_init(&inode->i_zombie, 1);
spin_lock_init(&inode->i_data.i_shared_lock);
@@ -518,7 +519,7 @@
inode->i_sb->s_op->clear_inode(inode);
if (inode->i_bdev) {
bdput(inode->i_bdev);
- inode->i_bdev = NULL;
+ bd_forget(inode);
}
if (inode->i_cdev) {
cdput(inode->i_cdev);
diff -urN S10-pre13-new/include/linux/fs.h S10-pre13-current/include/linux/fs.h
--- S10-pre13-new/include/linux/fs.h Fri Sep 21 09:45:29 2001
+++ S10-pre13-current/include/linux/fs.h Fri Sep 21 18:44:01 2001
@@ -415,6 +415,7 @@
int bd_cache_openers;
const struct block_device_operations *bd_op;
struct semaphore bd_sem; /* open/close mutex */
+ struct list_head bd_inodes;
};
struct inode {
@@ -452,6 +453,7 @@
int i_mapping_overload;
struct dquot *i_dquot[MAXQUOTAS];
/* These three should probably be a union */
+ struct list_head i_devices;
struct pipe_inode_info *i_pipe;
struct block_device *i_bdev;
struct char_device *i_cdev;
@@ -1046,6 +1048,8 @@
extern int register_blkdev(unsigned int, const char *, struct block_device_operations *);
extern int unregister_blkdev(unsigned int, const char *);
extern struct block_device *bdget(dev_t);
+extern int bd_acquire(struct inode *inode);
+extern void bd_forget(struct inode *inode);
extern void bdput(struct block_device *);
extern struct char_device *cdget(dev_t);
extern void cdput(struct char_device *);