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authorNick Piggin <npiggin@kernel.dk>2011-01-07 01:49:49 -0500
committerNick Piggin <npiggin@kernel.dk>2011-01-07 01:50:26 -0500
commitfa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9 (patch)
tree203e0f73883e4c26b5597e36042386a1237dab35 /fs/fat/inode.c
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/fat/inode.c')
-rw-r--r--fs/fat/inode.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index ad6998a92c30..8cccfebee180 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -514,11 +514,18 @@ static struct inode *fat_alloc_inode(struct super_block *sb)
514 return &ei->vfs_inode; 514 return &ei->vfs_inode;
515} 515}
516 516
517static void fat_destroy_inode(struct inode *inode) 517static void fat_i_callback(struct rcu_head *head)
518{ 518{
519 struct inode *inode = container_of(head, struct inode, i_rcu);
520 INIT_LIST_HEAD(&inode->i_dentry);
519 kmem_cache_free(fat_inode_cachep, MSDOS_I(inode)); 521 kmem_cache_free(fat_inode_cachep, MSDOS_I(inode));
520} 522}
521 523
524static void fat_destroy_inode(struct inode *inode)
525{
526 call_rcu(&inode->i_rcu, fat_i_callback);
527}
528
522static void init_once(void *foo) 529static void init_once(void *foo)
523{ 530{
524 struct msdos_inode_info *ei = (struct msdos_inode_info *)foo; 531 struct msdos_inode_info *ei = (struct msdos_inode_info *)foo;