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Subject[PATCH 6/6] vfs: split __lookup_hash
Date
From: Miklos Szeredi <mszeredi@suse.cz>

Split __lookup_hash into two component functions:

lookup_dcache - tries cached lookup, returns whether real lookup is needed
lookup_real - calls i_op->lookup

This eliminates code duplication between d_alloc_and_lookup() and
d_inode_lookup().

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/namei.c | 103 +++++++++++++++++++++++++----------------------------------
1 files changed, 44 insertions(+), 59 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index d500cb0..d15d0ba 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1058,53 +1058,65 @@ static void follow_dotdot(struct nameidata *nd)
}

/*
- * Allocate a dentry with name and parent, and perform a parent
- * directory ->lookup on it. Returns the new dentry, or ERR_PTR
- * on error. parent->d_inode->i_mutex must be held. d_lookup must
- * have verified that no child exists while under i_mutex.
+ * This looks up the name in dcache, possibly revalidates the old dentry and
+ * allocates a new one if not found or not valid. In the need_lookup argument
+ * returns whether i_op->lookup is necessary.
+ *
+ * dir->d_inode->i_mutex must be held
*/
-static struct dentry *d_alloc_and_lookup(struct dentry *parent,
- struct qstr *name, struct nameidata *nd)
+static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
+ struct nameidata *nd, bool *need_lookup)
{
- struct inode *inode = parent->d_inode;
struct dentry *dentry;
- struct dentry *old;
+ int error;

- /* Don't create child dentry for a dead directory. */
- if (unlikely(IS_DEADDIR(inode)))
- return ERR_PTR(-ENOENT);
+ *need_lookup = false;
+ dentry = d_lookup(dir, name);
+ if (dentry) {
+ if (d_need_lookup(dentry)) {
+ *need_lookup = true;
+ } else if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
+ error = d_revalidate(dentry, nd);
+ if (unlikely(error <= 0)) {
+ if (error < 0) {
+ dput(dentry);
+ return ERR_PTR(error);
+ } else if (!d_invalidate(dentry)) {
+ dput(dentry);
+ dentry = NULL;
+ }
+ }
+ }
+ }

- dentry = d_alloc(parent, name);
- if (unlikely(!dentry))
- return ERR_PTR(-ENOMEM);
+ if (!dentry) {
+ dentry = d_alloc(dir, name);
+ if (unlikely(!dentry))
+ return ERR_PTR(-ENOMEM);

- old = inode->i_op->lookup(inode, dentry, nd);
- if (unlikely(old)) {
- dput(dentry);
- dentry = old;
+ *need_lookup = true;
}
return dentry;
}

/*
- * We already have a dentry, but require a lookup to be performed on the parent
- * directory to fill in d_inode. Returns the new dentry, or ERR_PTR on error.
- * parent->d_inode->i_mutex must be held. d_lookup must have verified that no
- * child exists while under i_mutex.
+ * Call i_op->lookup on the dentry. The dentry must be negative but may be
+ * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
+ *
+ * dir->d_inode->i_mutex must be held
*/
-static struct dentry *d_inode_lookup(struct dentry *parent, struct dentry *dentry,
- struct nameidata *nd)
+static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
+ struct nameidata *nd)
{
- struct inode *inode = parent->d_inode;
struct dentry *old;

/* Don't create child dentry for a dead directory. */
- if (unlikely(IS_DEADDIR(inode))) {
+ if (unlikely(IS_DEADDIR(dir))) {
dput(dentry);
return ERR_PTR(-ENOENT);
}

- old = inode->i_op->lookup(inode, dentry, nd);
+ old = dir->i_op->lookup(dir, dentry, nd);
if (unlikely(old)) {
dput(dentry);
dentry = old;
@@ -1115,41 +1127,14 @@ static struct dentry *d_inode_lookup(struct dentry *parent, struct dentry *dentr
static struct dentry *__lookup_hash(struct qstr *name, struct dentry *base,
struct nameidata *nd)
{
+ bool need_lookup;
struct dentry *dentry;

- dentry = d_lookup(base, name);
-
- if (dentry && d_need_lookup(dentry)) {
- /*
- * __lookup_hash is called with the parent dir's i_mutex already
- * held, so we are good to go here.
- */
- return d_inode_lookup(base, dentry, nd);
- }
+ dentry = lookup_dcache(name, base, nd, &need_lookup);
+ if (!need_lookup)
+ return dentry;

- if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE)) {
- int status = d_revalidate(dentry, nd);
- if (unlikely(status <= 0)) {
- /*
- * The dentry failed validation.
- * If d_revalidate returned 0 attempt to invalidate
- * the dentry otherwise d_revalidate is asking us
- * to return a fail status.
- */
- if (status < 0) {
- dput(dentry);
- return ERR_PTR(status);
- } else if (!d_invalidate(dentry)) {
- dput(dentry);
- dentry = NULL;
- }
- }
- }
-
- if (!dentry)
- dentry = d_alloc_and_lookup(base, name, nd);
-
- return dentry;
+ return lookup_real(base->d_inode, dentry, nd);
}

/*
--
1.7.7


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