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Subject[patch 37/52] fs: icache lazy lru
Impelemnt lazy inode lru similarly to dcache. This will reduce lock
acquisition and will help to improve lock ordering subsequently.

Signed-off-by: Nick Piggin <npiggin@suse.de>
---
fs/fs-writeback.c | 21 +++++++--------
fs/inode.c | 61 +++++++++++++++++++---------------------------
include/linux/fs.h | 7 ++++-
include/linux/writeback.h | 1
4 files changed, 42 insertions(+), 48 deletions(-)

Index: linux-2.6/fs/inode.c
===================================================================
--- linux-2.6.orig/fs/inode.c
+++ linux-2.6/fs/inode.c
@@ -96,7 +96,6 @@ static unsigned int i_hash_shift __read_
* allowing for low-overhead inode sync() operations.
*/

-LIST_HEAD(inode_in_use);
LIST_HEAD(inode_unused);

struct inode_hash_bucket {
@@ -298,6 +297,7 @@ void inode_init_once(struct inode *inode
INIT_HLIST_BL_NODE(&inode->i_hash);
INIT_LIST_HEAD(&inode->i_dentry);
INIT_LIST_HEAD(&inode->i_devices);
+ INIT_LIST_HEAD(&inode->i_list);
INIT_RADIX_TREE(&inode->i_data.page_tree, GFP_ATOMIC);
spin_lock_init(&inode->i_data.tree_lock);
spin_lock_init(&inode->i_data.i_mmap_lock);
@@ -323,25 +323,6 @@ static void init_once(void *foo)
inode_init_once(inode);
}

-/*
- * inode_lock must be held
- */
-void __iget(struct inode *inode)
-{
- assert_spin_locked(&inode->i_lock);
-
- inode->i_count++;
- if (inode->i_count > 1)
- return;
-
- if (!(inode->i_state & (I_DIRTY|I_SYNC))) {
- spin_lock(&wb_inode_list_lock);
- list_move(&inode->i_list, &inode_in_use);
- spin_unlock(&wb_inode_list_lock);
- }
- atomic_dec(&inodes_stat.nr_unused);
-}
-
/**
* clear_inode - clear an inode
* @inode: inode to clear
@@ -384,7 +365,7 @@ static void dispose_list(struct list_hea
struct inode *inode;

inode = list_first_entry(head, struct inode, i_list);
- list_del(&inode->i_list);
+ list_del_init(&inode->i_list);

if (inode->i_data.nrpages)
truncate_inode_pages(&inode->i_data, 0);
@@ -437,11 +418,12 @@ static int invalidate_list(struct list_h
invalidate_inode_buffers(inode);
if (!inode->i_count) {
spin_lock(&wb_inode_list_lock);
- list_move(&inode->i_list, dispose);
+ list_del(&inode->i_list);
spin_unlock(&wb_inode_list_lock);
WARN_ON(inode->i_state & I_NEW);
inode->i_state |= I_FREEING;
spin_unlock(&inode->i_lock);
+ list_add(&inode->i_list, dispose);
count++;
continue;
}
@@ -480,19 +462,6 @@ int invalidate_inodes(struct super_block
}
EXPORT_SYMBOL(invalidate_inodes);

-static int can_unuse(struct inode *inode)
-{
- if (inode->i_state)
- return 0;
- if (inode_has_buffers(inode))
- return 0;
- if (inode->i_count)
- return 0;
- if (inode->i_data.nrpages)
- return 0;
- return 1;
-}
-
/*
* Scan `goal' inodes on the unused list for freeable ones. They are moved to
* a temporary list and then are freed outside inode_lock by dispose_list().
@@ -510,13 +479,12 @@ static void prune_icache(int nr_to_scan)
{
LIST_HEAD(freeable);
int nr_pruned = 0;
- int nr_scanned;
unsigned long reap = 0;

down_read(&iprune_sem);
again:
spin_lock(&wb_inode_list_lock);
- for (nr_scanned = 0; nr_scanned < nr_to_scan; nr_scanned++) {
+ for (; nr_to_scan; nr_to_scan--) {
struct inode *inode;

if (list_empty(&inode_unused))
@@ -528,33 +496,30 @@ again:
spin_unlock(&wb_inode_list_lock);
goto again;
}
- if (inode->i_state || inode->i_count) {
+ if (inode->i_count || (inode->i_state & ~I_REFERENCED)) {
+ list_del_init(&inode->i_list);
+ spin_unlock(&inode->i_lock);
+ atomic_dec(&inodes_stat.nr_unused);
+ continue;
+ }
+ if (inode->i_state) {
list_move(&inode->i_list, &inode_unused);
+ inode->i_state &= ~I_REFERENCED;
spin_unlock(&inode->i_lock);
continue;
}
if (inode_has_buffers(inode) || inode->i_data.nrpages) {
+ list_move(&inode->i_list, &inode_unused);
spin_unlock(&wb_inode_list_lock);
__iget(inode);
spin_unlock(&inode->i_lock);
+
if (remove_inode_buffers(inode))
reap += invalidate_mapping_pages(&inode->i_data,
0, -1);
iput(inode);
-again2:
spin_lock(&wb_inode_list_lock);
-
- if (inode != list_entry(inode_unused.next,
- struct inode, i_list))
- continue; /* wrong inode or list_empty */
- if (!spin_trylock(&inode->i_lock)) {
- spin_unlock(&wb_inode_list_lock);
- goto again2;
- }
- if (!can_unuse(inode)) {
- spin_unlock(&inode->i_lock);
- continue;
- }
+ continue;
}
list_move(&inode->i_list, &freeable);
WARN_ON(inode->i_state & I_NEW);
@@ -694,9 +659,6 @@ __inode_add_to_lists(struct super_block
atomic_inc(&inodes_stat.nr_inodes);
list_add(&inode->i_sb_list, &sb->s_inodes);
spin_unlock(&sb_inode_list_lock);
- spin_lock(&wb_inode_list_lock);
- list_add(&inode->i_list, &inode_in_use);
- spin_unlock(&wb_inode_list_lock);
if (b) {
spin_lock_bucket(b);
hlist_bl_add_head(&inode->i_hash, &b->head);
@@ -1343,9 +1305,13 @@ void generic_delete_inode(struct inode *
{
const struct super_operations *op = inode->i_sb->s_op;

- spin_lock(&wb_inode_list_lock);
- list_del_init(&inode->i_list);
- spin_unlock(&wb_inode_list_lock);
+ if (!list_empty(&inode->i_list)) {
+ spin_lock(&wb_inode_list_lock);
+ list_del_init(&inode->i_list);
+ spin_unlock(&wb_inode_list_lock);
+ if (!inode->i_state)
+ atomic_dec(&inodes_stat.nr_unused);
+ }
list_del_init(&inode->i_sb_list);
spin_unlock(&sb_inode_list_lock);
WARN_ON(inode->i_state & I_NEW);
@@ -1393,13 +1359,15 @@ int generic_detach_inode(struct inode *i
struct super_block *sb = inode->i_sb;

if (!hlist_bl_unhashed(&inode->i_hash)) {
- if (!(inode->i_state & (I_DIRTY|I_SYNC))) {
- spin_lock(&wb_inode_list_lock);
- list_move(&inode->i_list, &inode_unused);
- spin_unlock(&wb_inode_list_lock);
- }
- atomic_inc(&inodes_stat.nr_unused);
if (sb->s_flags & MS_ACTIVE) {
+ inode->i_state |= I_REFERENCED;
+ if (!(inode->i_state & (I_DIRTY|I_SYNC)) &&
+ list_empty(&inode->i_list)) {
+ spin_lock(&wb_inode_list_lock);
+ list_add(&inode->i_list, &inode_unused);
+ spin_unlock(&wb_inode_list_lock);
+ atomic_inc(&inodes_stat.nr_unused);
+ }
spin_unlock(&inode->i_lock);
spin_unlock(&sb_inode_list_lock);
return 0;
@@ -1414,11 +1382,14 @@ int generic_detach_inode(struct inode *i
WARN_ON(inode->i_state & I_NEW);
inode->i_state &= ~I_WILL_FREE;
__remove_inode_hash(inode);
- atomic_dec(&inodes_stat.nr_unused);
}
- spin_lock(&wb_inode_list_lock);
- list_del_init(&inode->i_list);
- spin_unlock(&wb_inode_list_lock);
+ if (!list_empty(&inode->i_list)) {
+ spin_lock(&wb_inode_list_lock);
+ list_del_init(&inode->i_list);
+ spin_unlock(&wb_inode_list_lock);
+ if (!inode->i_state)
+ atomic_dec(&inodes_stat.nr_unused);
+ }
list_del_init(&inode->i_sb_list);
spin_unlock(&sb_inode_list_lock);
WARN_ON(inode->i_state & I_NEW);
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h
+++ linux-2.6/include/linux/fs.h
@@ -1634,16 +1634,17 @@ struct super_operations {
*
* Q: What is the difference between I_WILL_FREE and I_FREEING?
*/
-#define I_DIRTY_SYNC 1
-#define I_DIRTY_DATASYNC 2
-#define I_DIRTY_PAGES 4
+#define I_DIRTY_SYNC 0x01
+#define I_DIRTY_DATASYNC 0x02
+#define I_DIRTY_PAGES 0x04
#define __I_NEW 3
#define I_NEW (1 << __I_NEW)
-#define I_WILL_FREE 16
-#define I_FREEING 32
-#define I_CLEAR 64
+#define I_WILL_FREE 0x10
+#define I_FREEING 0x20
+#define I_CLEAR 0x40
#define __I_SYNC 7
#define I_SYNC (1 << __I_SYNC)
+#define I_REFERENCED 0x100

#define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES)

@@ -2171,7 +2172,6 @@ extern int insert_inode_locked4(struct i
extern int insert_inode_locked(struct inode *);
extern void unlock_new_inode(struct inode *);

-extern void __iget(struct inode * inode);
extern void iget_failed(struct inode *);
extern void clear_inode(struct inode *);
extern void destroy_inode(struct inode *);
@@ -2422,6 +2422,12 @@ extern int generic_show_options(struct s
extern void save_mount_options(struct super_block *sb, char *options);
extern void replace_mount_options(struct super_block *sb, char *options);

+static inline void __iget(struct inode *inode)
+{
+ assert_spin_locked(&inode->i_lock);
+ inode->i_count++;
+}
+
static inline ino_t parent_ino(struct dentry *dentry)
{
ino_t res;
Index: linux-2.6/fs/fs-writeback.c
===================================================================
--- linux-2.6.orig/fs/fs-writeback.c
+++ linux-2.6/fs/fs-writeback.c
@@ -552,15 +552,8 @@ select_queue:
inode->i_state |= I_DIRTY_PAGES;
redirty_tail(inode);
}
- } else if (inode->i_count) {
- /*
- * The inode is clean, inuse
- */
- list_move(&inode->i_list, &inode_in_use);
} else {
- /*
- * The inode is clean, unused
- */
+ /* The inode is clean */
list_move(&inode->i_list, &inode_unused);
}
}
@@ -1206,8 +1199,6 @@ static void wait_sb_inodes(struct super_
*/
WARN_ON(!rwsem_is_locked(&sb->s_umount));

- spin_lock(&sb_inode_list_lock);
-
/*
* Data integrity sync. Must wait for all pages under writeback,
* because there may have been pages dirtied before our sync
@@ -1215,7 +1206,8 @@ static void wait_sb_inodes(struct super_
* In which case, the inode may not be on the dirty list, but
* we still have to wait for that writeout.
*/
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(inode, &sb->s_inodes, i_sb_list) {
struct address_space *mapping;

mapping = inode->i_mapping;
@@ -1229,13 +1221,13 @@ static void wait_sb_inodes(struct super_
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&sb_inode_list_lock);
+ rcu_read_unlock();
/*
* We hold a reference to 'inode' so it couldn't have been
- * removed from s_inodes list while we dropped the
- * sb_inode_list_lock. We cannot iput the inode now as we can
- * be holding the last reference and we cannot iput it under
- * spinlock. So we keep the reference and iput it later.
+ * removed from s_inodes list while we dropped the i_lock. We
+ * cannot iput the inode now as we can be holding the last
+ * reference and we cannot iput it under spinlock. So we keep
+ * the reference and iput it later.
*/
iput(old_inode);
old_inode = inode;
@@ -1244,9 +1236,9 @@ static void wait_sb_inodes(struct super_

cond_resched();

- spin_lock(&sb_inode_list_lock);
+ rcu_read_lock();
}
- spin_unlock(&sb_inode_list_lock);
+ rcu_read_unlock();
iput(old_inode);
}

Index: linux-2.6/include/linux/writeback.h
===================================================================
--- linux-2.6.orig/include/linux/writeback.h
+++ linux-2.6/include/linux/writeback.h
@@ -11,7 +11,6 @@ struct backing_dev_info;

extern spinlock_t sb_inode_list_lock;
extern spinlock_t wb_inode_list_lock;
-extern struct list_head inode_in_use;
extern struct list_head inode_unused;

/*



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