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Subject[PATCH vfs-2.6 2/6] vfs: add d_ancestor()
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This adds d_ancestor() instead of d_isparent(), then use it.

If new_dentry == old_dentry, is_subdir() returns 1, looks strange.
"new_dentry == old_dentry" is not subdir obviously. But I'm not
checking callers for now, so this keeps current behavior.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---

fs/dcache.c | 45 +++++++++++++++++++++++----------------------
fs/namei.c | 22 ++++++++++------------
include/linux/dcache.h | 1 +
3 files changed, 34 insertions(+), 34 deletions(-)

diff -puN fs/dcache.c~dcache-cleanup-2 fs/dcache.c
--- vfs-2.6/fs/dcache.c~dcache-cleanup-2 2008-10-16 06:57:29.000000000 +0900
+++ vfs-2.6-hirofumi/fs/dcache.c 2008-10-16 06:57:29.000000000 +0900
@@ -1718,18 +1718,23 @@ void d_move(struct dentry * dentry, stru
spin_unlock(&dcache_lock);
}

-/*
- * Helper that returns 1 if p1 is a parent of p2, else 0
+/**
+ * d_ancestor - search for an ancestor
+ * @p1: ancestor dentry
+ * @p2: child dentry
+ *
+ * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
+ * an ancestor of p2, else NULL.
*/
-static int d_isparent(struct dentry *p1, struct dentry *p2)
+struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
{
struct dentry *p;

for (p = p2; !IS_ROOT(p); p = p->d_parent) {
if (p->d_parent == p1)
- return 1;
+ return p;
}
- return 0;
+ return NULL;
}

/*
@@ -1753,7 +1758,7 @@ static struct dentry *__d_unalias(struct

/* Check for loops */
ret = ERR_PTR(-ELOOP);
- if (d_isparent(alias, dentry))
+ if (d_ancestor(alias, dentry))
goto out_err;

/* See lock_rename() */
@@ -2153,31 +2158,27 @@ out:
* Caller must ensure that "new_dentry" is pinned before calling is_subdir()
*/

-int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
+int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
{
int result;
- struct dentry * saved = new_dentry;
unsigned long seq;

- /* need rcu_readlock to protect against the d_parent trashing due to
- * d_move
+ /* FIXME: This is old behavior, needed? Please check callers. */
+ if (new_dentry == old_dentry)
+ return 1;
+
+ /*
+ * Need rcu_readlock to protect against the d_parent trashing
+ * due to d_move
*/
rcu_read_lock();
- do {
+ do {
/* for restarting inner loop in case of seq retry */
- new_dentry = saved;
- result = 0;
seq = read_seqbegin(&rename_lock);
- for (;;) {
- if (new_dentry != old_dentry) {
- if (IS_ROOT(new_dentry))
- break;
- new_dentry = new_dentry->d_parent;
- continue;
- }
+ if (d_ancestor(old_dentry, new_dentry))
result = 1;
- break;
- }
+ else
+ result = 0;
} while (read_seqretry(&rename_lock, seq));
rcu_read_unlock();

diff -puN include/linux/dcache.h~dcache-cleanup-2 include/linux/dcache.h
--- vfs-2.6/include/linux/dcache.h~dcache-cleanup-2 2008-10-16 06:57:29.000000000 +0900
+++ vfs-2.6-hirofumi/include/linux/dcache.h 2008-10-16 06:57:29.000000000 +0900
@@ -287,6 +287,7 @@ static inline struct dentry *d_add_uniqu

/* used for rename() and baskets */
extern void d_move(struct dentry *, struct dentry *);
+extern struct dentry *d_ancestor(struct dentry *, struct dentry *);

/* appendix may either be NULL or be used for transname suffixes */
extern struct dentry * d_lookup(struct dentry *, struct qstr *);
diff -puN fs/namei.c~dcache-cleanup-2 fs/namei.c
--- vfs-2.6/fs/namei.c~dcache-cleanup-2 2008-10-16 06:57:29.000000000 +0900
+++ vfs-2.6-hirofumi/fs/namei.c 2008-10-16 06:57:29.000000000 +0900
@@ -1454,20 +1454,18 @@ struct dentry *lock_rename(struct dentry

mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);

- for (p = p1; !IS_ROOT(p); p = p->d_parent) {
- if (p->d_parent == p2) {
- mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
- mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
- return p;
- }
+ p = d_ancestor(p2, p1);
+ if (p) {
+ mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
+ mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
+ return p;
}

- for (p = p2; !IS_ROOT(p); p = p->d_parent) {
- if (p->d_parent == p1) {
- mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
- mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
- return p;
- }
+ p = d_ancestor(p1, p2);
+ if (p) {
+ mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
+ mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
+ return p;
}

mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
_

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