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Subject[5/5] eliminate inode waitqueue hashtable
On Sat, Aug 28, 2004 at 01:11:07PM -0700, William Lee Irwin III wrote:
> Eliminate the bh waitqueue hashtable using bit_waitqueue() via
> wait_on_bit() and wake_up_bit() to locate the waitqueue head associated
> with a bit.

Eliminate the inode waitqueue hashtable using bit_waitqueue() via
wait_on_bit() and wake_up_bit() to locate the waitqueue head associated
with a bit.

Index: wait-2.6.9-rc1-mm1/include/linux/fs.h
===================================================================
--- wait-2.6.9-rc1-mm1.orig/include/linux/fs.h 2004-08-28 09:43:24.899791040 -0700
+++ wait-2.6.9-rc1-mm1/include/linux/fs.h 2004-08-28 09:50:30.834039192 -0700
@@ -1057,6 +1057,7 @@
#define I_NEW 64

#define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES)
+#define __I_LOCK 3 /* I_LOCK == 1 << __I_LOCK */

extern void __mark_inode_dirty(struct inode *, int);
static inline void mark_inode_dirty(struct inode *inode)
Index: wait-2.6.9-rc1-mm1/fs/inode.c
===================================================================
--- wait-2.6.9-rc1-mm1.orig/fs/inode.c 2004-08-28 09:43:23.419016152 -0700
+++ wait-2.6.9-rc1-mm1/fs/inode.c 2004-08-28 09:50:30.827040256 -0700
@@ -1257,37 +1257,10 @@

#endif

-/*
- * Hashed waitqueues for wait_on_inode(). The table is pretty small - the
- * kernel doesn't lock many inodes at the same time.
- */
-#define I_WAIT_TABLE_ORDER 3
-static struct i_wait_queue_head {
- wait_queue_head_t wqh;
-} ____cacheline_aligned_in_smp i_wait_queue_heads[1<<I_WAIT_TABLE_ORDER];
-
-/*
- * Return the address of the waitqueue_head to be used for this inode
- */
-static wait_queue_head_t *i_waitq_head(struct inode *inode)
+int inode_wait(void *word)
{
- return &i_wait_queue_heads[hash_ptr(inode, I_WAIT_TABLE_ORDER)].wqh;
-}
-
-void __wait_on_inode(struct inode *inode)
-{
- DECLARE_WAITQUEUE(wait, current);
- wait_queue_head_t *wq = i_waitq_head(inode);
-
- add_wait_queue(wq, &wait);
-repeat:
- set_current_state(TASK_UNINTERRUPTIBLE);
- if (inode->i_state & I_LOCK) {
- schedule();
- goto repeat;
- }
- remove_wait_queue(wq, &wait);
- __set_current_state(TASK_RUNNING);
+ schedule();
+ return 0;
}

/*
@@ -1296,36 +1269,39 @@
* that it isn't found. This is because iget will immediately call
* ->read_inode, and we want to be sure that evidence of the deletion is found
* by ->read_inode.
- *
- * This call might return early if an inode which shares the waitq is woken up.
- * This is most easily handled by the caller which will loop around again
- * looking for the inode.
- *
* This is called with inode_lock held.
*/
static void __wait_on_freeing_inode(struct inode *inode)
{
- DECLARE_WAITQUEUE(wait, current);
- wait_queue_head_t *wq = i_waitq_head(inode);
+ wait_queue_head_t *wq;
+ DEFINE_WAIT_BIT(wait, &inode->i_state, __I_LOCK);

- add_wait_queue(wq, &wait);
- set_current_state(TASK_UNINTERRUPTIBLE);
+ /*
+ * I_FREEING and I_CLEAR are cleared in process context under
+ * inode_lock, so we have to give the tasks who would clear them
+ * a chance to run and acquire inode_lock.
+ */
+ if (!(inode->i_state & I_LOCK)) {
+ spin_unlock(&inode_lock);
+ yield();
+ spin_lock(&inode_lock);
+ return;
+ }
+ wq = bit_waitqueue(&inode->i_state, __I_LOCK);
+ prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
spin_unlock(&inode_lock);
schedule();
- remove_wait_queue(wq, &wait);
+ finish_wait(wq, &wait.wait);
spin_lock(&inode_lock);
}

void wake_up_inode(struct inode *inode)
{
- wait_queue_head_t *wq = i_waitq_head(inode);
-
/*
* Prevent speculative execution through spin_unlock(&inode_lock);
*/
smp_mb();
- if (waitqueue_active(wq))
- wake_up_all(wq);
+ wake_up_bit(&inode->i_state, __I_LOCK);
}
EXPORT_SYMBOL(wake_up_inode);

@@ -1361,11 +1337,6 @@

void __init inode_init(unsigned long mempages)
{
- int i;
-
- for (i = 0; i < ARRAY_SIZE(i_wait_queue_heads); i++)
- init_waitqueue_head(&i_wait_queue_heads[i].wqh);
-
/* inode slab cache */
inode_cachep = kmem_cache_create("inode_cache", sizeof(struct inode),
0, SLAB_PANIC, init_once, NULL);
Index: wait-2.6.9-rc1-mm1/kernel/wait.c
===================================================================
--- wait-2.6.9-rc1-mm1.orig/kernel/wait.c 2004-08-28 09:49:39.456849712 -0700
+++ wait-2.6.9-rc1-mm1/kernel/wait.c 2004-08-28 09:50:30.842037976 -0700
@@ -7,6 +7,7 @@
#include <linux/init.h>
#include <linux/module.h>
#include <linux/sched.h>
+#include <linux/mm.h>
#include <linux/wait.h>
#include <linux/hash.h>

Index: wait-2.6.9-rc1-mm1/fs/fs-writeback.c
===================================================================
--- wait-2.6.9-rc1-mm1.orig/fs/fs-writeback.c 2004-08-28 09:43:21.401322888 -0700
+++ wait-2.6.9-rc1-mm1/fs/fs-writeback.c 2004-08-28 09:50:30.840038280 -0700
@@ -240,6 +240,8 @@
__writeback_single_inode(struct inode *inode,
struct writeback_control *wbc)
{
+ wait_queue_head_t *wqh;
+
if ((wbc->sync_mode != WB_SYNC_ALL) && (inode->i_state & I_LOCK)) {
list_move(&inode->i_list, &inode->i_sb->s_dirty);
return 0;
@@ -248,12 +250,18 @@
/*
* It's a data-integrity sync. We must wait.
*/
- while (inode->i_state & I_LOCK) {
- __iget(inode);
- spin_unlock(&inode_lock);
- __wait_on_inode(inode);
- iput(inode);
- spin_lock(&inode_lock);
+ if (inode->i_state & I_LOCK) {
+ DEFINE_WAIT_BIT(wq, &inode->i_state, __I_LOCK);
+
+ wqh = bit_waitqueue(&inode->i_state, __I_LOCK);
+ do {
+ __iget(inode);
+ spin_unlock(&inode_lock);
+ __wait_on_bit(wqh, &wq, &inode->i_state, __I_LOCK,
+ inode_wait, TASK_UNINTERRUPTIBLE);
+ iput(inode);
+ spin_lock(&inode_lock);
+ } while (inode->i_state & I_LOCK);
}
return __sync_single_inode(inode, wbc);
}
Index: wait-2.6.9-rc1-mm1/include/linux/writeback.h
===================================================================
--- wait-2.6.9-rc1-mm1.orig/include/linux/writeback.h 2004-08-28 09:43:02.320223656 -0700
+++ wait-2.6.9-rc1-mm1/include/linux/writeback.h 2004-08-28 09:50:30.836038888 -0700
@@ -68,7 +68,7 @@
*/
void writeback_inodes(struct writeback_control *wbc);
void wake_up_inode(struct inode *inode);
-void __wait_on_inode(struct inode * inode);
+int inode_wait(void *);
void sync_inodes_sb(struct super_block *, int wait);
void sync_inodes(int wait);

@@ -76,8 +76,8 @@
static inline void wait_on_inode(struct inode *inode)
{
might_sleep();
- if (inode->i_state & I_LOCK)
- __wait_on_inode(inode);
+ wait_on_bit(&inode->i_state, __I_LOCK, inode_wait,
+ TASK_UNINTERRUPTIBLE);
}

/*
-
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