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fs: Stop abusing find_inode_fast in iunique 

Stop abusing find_inode_fast for iunique and opencode the inode hash walk.
Introduce a new iunique_lock to protect the iunique counters once inode_lock
is removed.

Based on a patch originally from Nick Piggin.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig 2010-10-23 07:00:16 -04:00 committed by Al Viro
parent 4c51acbc66
commit ad5e195ac9
1 changed files with 25 additions and 5 deletions
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30
fs/inode.c
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@ -884,6 +884,27 @@ 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_head *b = inode_hashtable + hash(sb, ino);
struct hlist_node *node;
struct inode *inode;
hlist_for_each_entry(inode, node, b, i_hash) {
if (inode->i_ino == ino && inode->i_sb == sb)
return 0;
}
return 1;
}
/**
* iunique - get a unique inode number
* @sb: superblock
@ -905,19 +926,18 @@ 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_head *head;
ino_t res;
spin_lock(&inode_lock);
spin_lock(&iunique_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);
} while (inode != NULL);
} while (!test_inode_iunique(sb, res));
spin_unlock(&iunique_lock);
spin_unlock(&inode_lock);
return res;