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Subject[PATCH 15/19] fs: Make iunique independent of inode_lock
Date
From: Nick Piggin <npiggin@suse.de>

Before removing the inode_lock, the iunique counter needs to be made
independent of the inode_lock. Add a new lock to protect the iunique
counter and nest it inside the inode_lock to provide the same
protection that the inode_lock currently provides.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
fs/inode.c | 35 ++++++++++++++++++++++++++++-------
1 files changed, 28 insertions(+), 7 deletions(-)
diff --git a/fs/inode.c b/fs/inode.c
index 05852a1..6526d70 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1063,6 +1063,30 @@ static struct inode *get_new_inode_fast(struct super_block *sb,
return inode;
}

+/*
+ * search the inode cache for a matching inode number.
+ * If we find one, then the inode number we are trying to
+ * allocate is not unique and so we should not use it.
+ *
+ * Returns 1 if the inode number is unique, 0 if it is not.
+ */
+static int test_inode_iunique(struct super_block * sb, unsigned long ino)
+{
+ struct hlist_bl_head *b = inode_hashtable + hash(sb, ino);
+ struct hlist_bl_node *node;
+ struct inode *inode;
+
+ hlist_bl_lock(b);
+ hlist_bl_for_each_entry(inode, node, b, i_hash) {
+ if (inode->i_ino == ino && inode->i_sb == sb) {
+ hlist_bl_unlock(b);
+ return 0;
+ }
+ }
+ hlist_bl_unlock(b);
+ return 1;
+}
+
/**
* iunique - get a unique inode number
* @sb: superblock
@@ -1084,20 +1108,17 @@ ino_t iunique(struct super_block *sb, ino_t max_reserved)
* error if st_ino won't fit in target struct field. Use 32bit counter
* here to attempt to avoid that.
*/
+ static DEFINE_SPINLOCK(iunique_lock);
static unsigned int counter;
- struct inode *inode;
- struct hlist_bl_head *b;
ino_t res;

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

return res;
}
--
1.7.1


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