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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/block_dev.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/block_dev.c')
-rw-r--r--fs/block_dev.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 4230252fd689..771f23527010 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -409,13 +409,20 @@ static struct inode *bdev_alloc_inode(struct super_block *sb)
409 return &ei->vfs_inode; 409 return &ei->vfs_inode;
410} 410}
411 411
412static void bdev_destroy_inode(struct inode *inode) 412static void bdev_i_callback(struct rcu_head *head)
413{ 413{
414 struct inode *inode = container_of(head, struct inode, i_rcu);
414 struct bdev_inode *bdi = BDEV_I(inode); 415 struct bdev_inode *bdi = BDEV_I(inode);
415 416
417 INIT_LIST_HEAD(&inode->i_dentry);
416 kmem_cache_free(bdev_cachep, bdi); 418 kmem_cache_free(bdev_cachep, bdi);
417} 419}
418 420
421static void bdev_destroy_inode(struct inode *inode)
422{
423 call_rcu(&inode->i_rcu, bdev_i_callback);
424}
425
419static void init_once(void *foo) 426static void init_once(void *foo)
420{ 427{
421 struct bdev_inode *ei = (struct bdev_inode *) foo; 428 struct bdev_inode *ei = (struct bdev_inode *) foo;