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Date: Wed, 29 Sep 2010 22:18:39 +1000
From: Dave Chinner <david@...morbit.com>
To: linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH 07/17] fs: icache atomic inodes_stat
From: Nick Piggin <npiggin@...e.de>
The inode use statistics are currently protected by the inode_lock.
Before we can remove the inode_lock, we need to protect these
counters against races. Do this by converting them to atomic
counters so they ar enot dependent on any lock at all.
Signed-off-by: Nick Piggin <npiggin@...e.de>
Signed-off-by: Dave Chinner <dchinner@...hat.com>
---
fs/fs-writeback.c | 6 ++++--
fs/inode.c | 26 ++++++++++++++------------
include/linux/fs.h | 13 ++++++-------
3 files changed, 24 insertions(+), 21 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index fb7b723..f6c8975 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -764,7 +764,8 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
wb->last_old_flush = jiffies;
nr_pages = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS) +
- (inodes_stat.nr_inodes - inodes_stat.nr_unused);
+ (atomic_read(&inodes_stat.nr_inodes) -
+ atomic_read(&inodes_stat.nr_unused));
if (nr_pages) {
struct wb_writeback_work work = {
@@ -1144,7 +1145,8 @@ void writeback_inodes_sb(struct super_block *sb)
WARN_ON(!rwsem_is_locked(&sb->s_umount));
work.nr_pages = nr_dirty + nr_unstable +
- (inodes_stat.nr_inodes - inodes_stat.nr_unused);
+ (atomic_read(&inodes_stat.nr_inodes) -
+ atomic_read(&inodes_stat.nr_unused));
bdi_queue_work(sb->s_bdi, &work);
wait_for_completion(&done);
diff --git a/fs/inode.c b/fs/inode.c
index e15620f..6d982e6 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -122,7 +122,10 @@ static DECLARE_RWSEM(iprune_sem);
/*
* Statistics gathering..
*/
-struct inodes_stat_t inodes_stat;
+struct inodes_stat_t inodes_stat = {
+ .nr_inodes = ATOMIC_INIT(0),
+ .nr_unused = ATOMIC_INIT(0),
+};
static struct kmem_cache *inode_cachep __read_mostly;
@@ -313,7 +316,7 @@ void __iget(struct inode *inode)
list_move(&inode->i_list, &inode_in_use);
spin_unlock(&wb_inode_list_lock);
}
- inodes_stat.nr_unused--;
+ atomic_dec(&inodes_stat.nr_unused);
}
void end_writeback(struct inode *inode)
@@ -377,9 +380,7 @@ static void dispose_list(struct list_head *head)
destroy_inode(inode);
nr_disposed++;
}
- spin_lock(&inode_lock);
- inodes_stat.nr_inodes -= nr_disposed;
- spin_unlock(&inode_lock);
+ atomic_sub(nr_disposed, &inodes_stat.nr_inodes);
}
/*
@@ -428,7 +429,7 @@ static int invalidate_list(struct list_head *head, struct list_head *dispose)
busy = 1;
}
/* only unused inodes may be cached with i_count zero */
- inodes_stat.nr_unused -= count;
+ atomic_sub(count, &inodes_stat.nr_unused);
return busy;
}
@@ -545,7 +546,7 @@ again2:
spin_unlock(&inode->i_lock);
nr_pruned++;
}
- inodes_stat.nr_unused -= nr_pruned;
+ atomic_sub(nr_pruned, &inodes_stat.nr_unused);
if (current_is_kswapd())
__count_vm_events(KSWAPD_INODESTEAL, reap);
else
@@ -578,7 +579,8 @@ static int shrink_icache_memory(struct shrinker *shrink, int nr, gfp_t gfp_mask)
return -1;
prune_icache(nr);
}
- return (inodes_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
+ return (atomic_read(&inodes_stat.nr_unused) / 100) *
+ sysctl_vfs_cache_pressure;
}
static struct shrinker icache_shrinker = {
@@ -671,7 +673,7 @@ static inline void
__inode_add_to_lists(struct super_block *sb, struct hlist_head *head,
struct inode *inode)
{
- inodes_stat.nr_inodes++;
+ atomic_inc(&inodes_stat.nr_inodes);
spin_lock(&sb_inode_list_lock);
list_add(&inode->i_sb_list, &sb->s_inodes);
spin_unlock(&sb_inode_list_lock);
@@ -1336,7 +1338,7 @@ static void iput_final(struct inode *inode)
list_move(&inode->i_list, &inode_unused);
spin_unlock(&wb_inode_list_lock);
}
- inodes_stat.nr_unused++;
+ atomic_inc(&inodes_stat.nr_unused);
if (sb->s_flags & MS_ACTIVE) {
spin_unlock(&inode->i_lock);
spin_unlock(&sb_inode_list_lock);
@@ -1354,7 +1356,7 @@ static void iput_final(struct inode *inode)
spin_lock(&inode->i_lock);
WARN_ON(inode->i_state & I_NEW);
inode->i_state &= ~I_WILL_FREE;
- inodes_stat.nr_unused--;
+ atomic_dec(&inodes_stat.nr_unused);
spin_lock(&inode_hash_lock);
hlist_del_init(&inode->i_hash);
spin_unlock(&inode_hash_lock);
@@ -1366,9 +1368,9 @@ static void iput_final(struct inode *inode)
spin_unlock(&sb_inode_list_lock);
WARN_ON(inode->i_state & I_NEW);
inode->i_state |= I_FREEING;
- inodes_stat.nr_inodes--;
spin_unlock(&inode->i_lock);
spin_unlock(&inode_lock);
+ atomic_dec(&inodes_stat.nr_inodes);
evict(inode);
spin_lock(&inode_lock);
spin_lock(&inode_hash_lock);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 415c88e..d60f256 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -39,13 +39,6 @@ struct files_stat_struct {
int max_files; /* tunable */
};
-struct inodes_stat_t {
- int nr_inodes;
- int nr_unused;
- int dummy[5]; /* padding for sysctl ABI compatibility */
-};
-
-
#define NR_FILE 8192 /* this can well be larger on a larger system */
#define MAY_EXEC 1
@@ -416,6 +409,12 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
ssize_t bytes, void *private, int ret,
bool is_async);
+struct inodes_stat_t {
+ atomic_t nr_inodes;
+ atomic_t nr_unused;
+ int dummy[5]; /* padding for sysctl ABI compatibility */
+};
+
/*
* Attribute flags. These should be or-ed together to figure out what
* has been changed!
--
1.7.1
--
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