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authorNick Piggin <npiggin@kernel.dk>2011-01-07 17:49:49 +1100
committerNick Piggin <npiggin@kernel.dk>2011-01-07 17:50:26 +1100
commitfa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9 (patch)
tree203e0f73883e4c26b5597e36042386a1237dab35 /fs/jfs
parent77812a1ef139d84270d27faacc0630c887411013 (diff)
fs: icache RCU free inodes
RCU free the struct inode. This will allow: - Subsequent store-free path walking patch. The inode must be consulted for permissions when walking, so an RCU inode reference is a must. - sb_inode_list_lock to be moved inside i_lock because sb list walkers who want to take i_lock no longer need to take sb_inode_list_lock to walk the list in the first place. This will simplify and optimize locking. - Could remove some nested trylock loops in dcache code - Could potentially simplify things a bit in VM land. Do not need to take the page lock to follow page->mapping. The downsides of this is the performance cost of using RCU. In a simple creat/unlink microbenchmark, performance drops by about 10% due to inability to reuse cache-hot slab objects. As iterations increase and RCU freeing starts kicking over, this increases to about 20%. In cases where inode lifetimes are longer (ie. many inodes may be allocated during the average life span of a single inode), a lot of this cache reuse is not applicable, so the regression caused by this patch is smaller. The cache-hot regression could largely be avoided by using SLAB_DESTROY_BY_RCU, however this adds some complexity to list walking and store-free path walking, so I prefer to implement this at a later date, if it is shown to be a win in real situations. I haven't found a regression in any non-micro benchmark so I doubt it will be a problem. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Diffstat (limited to 'fs/jfs')
-rw-r--r--fs/jfs/super.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index 0669fc1cc3b..b715b0f7bdf 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -115,6 +115,14 @@ static struct inode *jfs_alloc_inode(struct super_block *sb)
return &jfs_inode->vfs_inode;
}
+static void jfs_i_callback(struct rcu_head *head)
+{
+ struct inode *inode = container_of(head, struct inode, i_rcu);
+ struct jfs_inode_info *ji = JFS_IP(inode);
+ INIT_LIST_HEAD(&inode->i_dentry);
+ kmem_cache_free(jfs_inode_cachep, ji);
+}
+
static void jfs_destroy_inode(struct inode *inode)
{
struct jfs_inode_info *ji = JFS_IP(inode);
@@ -128,7 +136,7 @@ static void jfs_destroy_inode(struct inode *inode)
ji->active_ag = -1;
}
spin_unlock_irq(&ji->ag_lock);
- kmem_cache_free(jfs_inode_cachep, ji);
+ call_rcu(&inode->i_rcu, jfs_i_callback);
}
static int jfs_statfs(struct dentry *dentry, struct kstatfs *buf)