[patch 33/52] fs: icache atomic last_ino, iunique lock

npiggin
2010-06-24T03:16:34Z

[-- Attachment #1: fs-inode_lock-scale-6c.patch --]
[-- Type: text/plain, Size: 2342 bytes --]

Make last_ino atomic in preperation for removing inode_lock.
Make a new lock for iunique counter, for removing inode_lock.

Signed-off-by: Nick Piggin <npiggin@suse.de>
---
fs/inode.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)

Index: linux-2.6/fs/inode.c
===================================================================
--- linux-2.6.orig/fs/inode.c
+++ linux-2.6/fs/inode.c
@@ -742,7 +742,7 @@ struct inode *new_inode(struct super_blo
* error if st_ino won't fit in target struct field. Use 32bit counter
* here to attempt to avoid that.
*/
- static unsigned int last_ino;
+ static atomic_t last_ino = ATOMIC_INIT(0);
struct inode *inode;

spin_lock_prefetch(&inode_lock);
@@ -752,7 +752,7 @@ struct inode *new_inode(struct super_blo
spin_lock(&inode_lock);
spin_lock(&sb_inode_list_lock);
spin_lock(&inode->i_lock);
- inode->i_ino = ++last_ino;
+ inode->i_ino = atomic_inc_return(&last_ino);
inode->i_state = 0;
__inode_add_to_lists(sb, NULL, inode);
spin_unlock(&inode->i_lock);
@@ -903,6 +903,22 @@ static struct inode *get_new_inode_fast(
return inode;
}

+static int test_inode_iunique(struct super_block * sb, struct hlist_head *head, unsigned long ino)
+{
+ struct hlist_node *node;
+ struct inode * inode = NULL;
+
+ spin_lock(&inode_hash_lock);
+ hlist_for_each_entry(inode, node, head, i_hash) {
+ if (inode->i_ino == ino && inode->i_sb == sb) {
+ spin_unlock(&inode_hash_lock);
+ return 0;
+ }
+ }
+ spin_unlock(&inode_hash_lock);
+ return 1;
+}
+
/**
* iunique - get a unique inode number
* @sb: superblock
@@ -924,20 +940,20 @@ ino_t iunique(struct super_block *sb, in
* error if st_ino won't fit in target struct field. Use 32bit counter
* here to attempt to avoid that.
*/
+ static DEFINE_SPINLOCK(unique_lock);
static unsigned int counter;
- struct inode *inode;
struct hlist_head *head;
ino_t res;

spin_lock(&inode_lock);
+ spin_lock(&unique_lock);
do {
if (counter <= max_reserved)
counter = max_reserved + 1;
res = counter++;
head = inode_hashtable + hash(sb, res);
- inode = find_inode_fast(sb, head, res);
- spin_unlock(&inode->i_lock);
- } while (inode != NULL);
+ } while (!test_inode_iunique(sb, head, res));
+ spin_unlock(&unique_lock);
spin_unlock(&inode_lock);

return res;