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Subject[PATCH 5/6] staging: lustre: llite: refine ll_find_alias based on d_exact_alias
The task of ll_find_alias() is now very similar to d_exact_alias().
We cannot use that function directory, but we can copy much of
the structure so that the similarities and differences are more
obvious.
Examining d_exact_alias() shows that the d_lock spinlock does not
need to be held as much as it currently is.

Signed-off-by: NeilBrown <neilb@suse.com>
---
drivers/staging/lustre/lustre/llite/namei.c | 30 ++++++++++++++++++---------
1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/drivers/staging/lustre/lustre/llite/namei.c b/drivers/staging/lustre/lustre/llite/namei.c
index 51838eed501a..8ed24ec1255d 100644
--- a/drivers/staging/lustre/lustre/llite/namei.c
+++ b/drivers/staging/lustre/lustre/llite/namei.c
@@ -379,6 +379,10 @@ void ll_i2gids(__u32 *suppgids, struct inode *i1, struct inode *i2)

/*
* Try to reuse unhashed or invalidated dentries.
+ * This is very similar to d_exact_alias(), and any changes in one should be
+ * considered for inclusion in the other. The differences are that we don't
+ * need an unhashed alias, and we don't want d_compare to be used for
+ * comparison.
*/
static struct dentry *ll_find_alias(struct inode *inode, struct dentry *dentry)
{
@@ -390,19 +394,25 @@ static struct dentry *ll_find_alias(struct inode *inode, struct dentry *dentry)
spin_lock(&inode->i_lock);
hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
LASSERT(alias != dentry);
+ /*
+ * Don't need alias->d_lock here, because aliases with
+ * d_parent == entry->d_parent are not subject to name or
+ * parent changes, because the parent inode i_mutex is held.
+ */

- spin_lock(&alias->d_lock);
- if (alias->d_parent == dentry->d_parent &&
- alias->d_name.hash == dentry->d_name.hash &&
- alias->d_name.len == dentry->d_name.len &&
+ if (alias->d_parent != dentry->d_parent)
+ continue;
+ if (alias->d_name.hash != dentry->d_name.hash)
+ continue;
+ if (alias->d_name.len != dentry->d_name.len ||
memcmp(alias->d_name.name, dentry->d_name.name,
- dentry->d_name.len) == 0) {
- dget_dlock(alias);
- spin_unlock(&alias->d_lock);
- spin_unlock(&inode->i_lock);
- return alias;
- }
+ dentry->d_name.len) != 0)
+ continue;
+ spin_lock(&alias->d_lock);
+ dget_dlock(alias);
spin_unlock(&alias->d_lock);
+ spin_unlock(&inode->i_lock);
+ return alias;
}
spin_unlock(&inode->i_lock);


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