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Subject[PATCH 14/21] fs: add a per-superblock lock for the inode list
Date
From: Dave Chinner <dchinner@redhat.com>

To allow removal of the inode_lock, we first need to protect the
superblock inode list with its own lock instead of using the
inode_lock. Add a lock to the superblock to protect this list and
nest the new lock inside the inode_lock around the list operations
it needs to protect.

Based on a patch originally from Nick Piggin.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
fs/drop_caches.c | 4 ++++
fs/fs-writeback.c | 4 ++++
fs/inode.c | 29 +++++++++++++++++++++++------
fs/notify/inode_mark.c | 3 +++
fs/quota/dquot.c | 6 ++++++
fs/super.c | 1 +
include/linux/fs.h | 1 +
7 files changed, 42 insertions(+), 6 deletions(-)
diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index 10c8c5a..dfe8cb1 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -17,6 +17,7 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
struct inode *inode, *toput_inode = NULL;

spin_lock(&inode_lock);
+ spin_lock(&sb->s_inodes_lock);
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
continue;
@@ -25,12 +26,15 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
spin_lock(&inode->i_lock);
inode->i_ref++;
spin_unlock(&inode->i_lock);
+ spin_unlock(&sb->s_inodes_lock);
spin_unlock(&inode_lock);
invalidate_mapping_pages(inode->i_mapping, 0, -1);
iput(toput_inode);
toput_inode = inode;
spin_lock(&inode_lock);
+ spin_lock(&sb->s_inodes_lock);
}
+ spin_unlock(&sb->s_inodes_lock);
spin_unlock(&inode_lock);
iput(toput_inode);
}
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 1fb5d95..676e048 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1031,6 +1031,7 @@ static void wait_sb_inodes(struct super_block *sb)
WARN_ON(!rwsem_is_locked(&sb->s_umount));

spin_lock(&inode_lock);
+ spin_lock(&sb->s_inodes_lock);

/*
* Data integrity sync. Must wait for all pages under writeback,
@@ -1050,6 +1051,7 @@ static void wait_sb_inodes(struct super_block *sb)
spin_lock(&inode->i_lock);
inode->i_ref++;
spin_unlock(&inode->i_lock);
+ spin_unlock(&sb->s_inodes_lock);
spin_unlock(&inode_lock);
/*
* We hold a reference to 'inode' so it couldn't have
@@ -1067,7 +1069,9 @@ static void wait_sb_inodes(struct super_block *sb)
cond_resched();

spin_lock(&inode_lock);
+ spin_lock(&sb->s_inodes_lock);
}
+ spin_unlock(&sb->s_inodes_lock);
spin_unlock(&inode_lock);
iput(old_inode);
}
diff --git a/fs/inode.c b/fs/inode.c
index da6b73b..734aadf 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -34,13 +34,18 @@
* i_ref
* inode hash lock protects:
* inode hash table, i_hash
+ * sb inode lock protects:
+ * s_inodes, i_sb_list
*
* Lock orders
* inode_lock
* inode hash bucket lock
* inode->i_lock
+ *
+ * inode_lock
+ * sb inode lock
+ * inode->i_lock
*/
-
/*
* This is needed for the following functions:
* - inode_has_buffers
@@ -365,9 +370,13 @@ void inode_lru_list_del(struct inode *inode)
}
}

-static inline void __inode_sb_list_add(struct inode *inode)
+static void __inode_sb_list_add(struct inode *inode)
{
- list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
+ struct super_block *sb = inode->i_sb;
+
+ spin_lock(&sb->s_inodes_lock);
+ list_add(&inode->i_sb_list, &sb->s_inodes);
+ spin_unlock(&sb->s_inodes_lock);
}

/**
@@ -382,9 +391,13 @@ void inode_sb_list_add(struct inode *inode)
}
EXPORT_SYMBOL_GPL(inode_sb_list_add);

-static inline void __inode_sb_list_del(struct inode *inode)
+static void __inode_sb_list_del(struct inode *inode)
{
+ struct super_block *sb = inode->i_sb;
+
+ spin_lock(&sb->s_inodes_lock);
list_del_init(&inode->i_sb_list);
+ spin_unlock(&sb->s_inodes_lock);
}

static unsigned long hash(struct super_block *sb, unsigned long hashval)
@@ -507,7 +520,8 @@ static void dispose_list(struct list_head *head)
/*
* Invalidate all inodes for a device.
*/
-static int invalidate_list(struct list_head *head, struct list_head *dispose)
+static int invalidate_list(struct super_block *sb, struct list_head *head,
+ struct list_head *dispose)
{
struct list_head *next;
int busy = 0;
@@ -524,6 +538,7 @@ static int invalidate_list(struct list_head *head, struct list_head *dispose)
* shrink_icache_memory() away.
*/
cond_resched_lock(&inode_lock);
+ cond_resched_lock(&sb->s_inodes_lock);

next = next->next;
if (tmp == head)
@@ -562,8 +577,10 @@ int invalidate_inodes(struct super_block *sb)

down_write(&iprune_sem);
spin_lock(&inode_lock);
+ spin_lock(&sb->s_inodes_lock);
fsnotify_unmount_inodes(&sb->s_inodes);
- busy = invalidate_list(&sb->s_inodes, &throw_away);
+ busy = invalidate_list(sb, &sb->s_inodes, &throw_away);
+ spin_unlock(&sb->s_inodes_lock);
spin_unlock(&inode_lock);

dispose_list(&throw_away);
diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
index 1a4c117..4ed0e43 100644
--- a/fs/notify/inode_mark.c
+++ b/fs/notify/inode_mark.c
@@ -242,6 +242,7 @@ void fsnotify_unmount_inodes(struct list_head *list)

list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
struct inode *need_iput_tmp;
+ struct super_block *sb = inode->i_sb;

/*
* We cannot iref() an inode in state I_FREEING,
@@ -290,6 +291,7 @@ void fsnotify_unmount_inodes(struct list_head *list)
* will be added since the umount has begun. Finally,
* iprune_mutex keeps shrink_icache_memory() away.
*/
+ spin_unlock(&sb->s_inodes_lock);
spin_unlock(&inode_lock);

if (need_iput_tmp)
@@ -303,5 +305,6 @@ void fsnotify_unmount_inodes(struct list_head *list)
iput(inode);

spin_lock(&inode_lock);
+ spin_lock(&sb->s_inodes_lock);
}
}
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 326df72..7ef5411 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -897,6 +897,7 @@ static void add_dquot_ref(struct super_block *sb, int type)
#endif

spin_lock(&inode_lock);
+ spin_lock(&sb->s_inodes_lock);
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
continue;
@@ -912,6 +913,7 @@ static void add_dquot_ref(struct super_block *sb, int type)
spin_lock(&inode->i_lock);
inode->i_ref++;
spin_unlock(&inode->i_lock);
+ spin_unlock(&sb->s_inodes_lock);
spin_unlock(&inode_lock);

iput(old_inode);
@@ -923,7 +925,9 @@ static void add_dquot_ref(struct super_block *sb, int type)
* keep the reference and iput it later. */
old_inode = inode;
spin_lock(&inode_lock);
+ spin_lock(&sb->s_inodes_lock);
}
+ spin_unlock(&sb->s_inodes_lock);
spin_unlock(&inode_lock);
iput(old_inode);

@@ -1006,6 +1010,7 @@ static void remove_dquot_ref(struct super_block *sb, int type,
int reserved = 0;

spin_lock(&inode_lock);
+ spin_lock(&sb->s_inodes_lock);
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
/*
* We have to scan also I_NEW inodes because they can already
@@ -1019,6 +1024,7 @@ static void remove_dquot_ref(struct super_block *sb, int type,
remove_inode_dquot_ref(inode, type, tofree_head);
}
}
+ spin_unlock(&sb->s_inodes_lock);
spin_unlock(&inode_lock);
#ifdef CONFIG_QUOTA_DEBUG
if (reserved) {
diff --git a/fs/super.c b/fs/super.c
index 8819e3a..c5332e5 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -76,6 +76,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
INIT_LIST_HEAD(&s->s_dentry_lru);
init_rwsem(&s->s_umount);
mutex_init(&s->s_lock);
+ spin_lock_init(&s->s_inodes_lock);
lockdep_set_class(&s->s_umount, &type->s_umount_key);
/*
* The locking rules for s_lock are up to the
diff --git a/include/linux/fs.h b/include/linux/fs.h
index adcbfb9..f222ce8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1347,6 +1347,7 @@ struct super_block {
#endif
const struct xattr_handler **s_xattr;

+ spinlock_t s_inodes_lock; /* lock for s_inodes */
struct list_head s_inodes; /* all inodes */
struct hlist_head s_anon; /* anonymous dentries for (nfs) exporting */
#ifdef CONFIG_SMP
--
1.7.1


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