[PATCH 6/7] lookup_fast(): don't bother with inode

Al Viro
2022-07-04T23:17:19Z

Note that validation of ->d_seq after ->d_inode fetch is gone, along
with fetching of ->d_inode itself.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/namei.c | 24 +++++-------------------
1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index fe95fe39634c..cdb61d09df79 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1617,8 +1617,7 @@ static struct dentry *__lookup_hash(const struct qstr *name,
return dentry;
}

-static struct dentry *lookup_fast(struct nameidata *nd,
- struct inode **inode)
+static struct dentry *lookup_fast(struct nameidata *nd)
{
struct dentry *dentry, *parent = nd->path.dentry;
int status = 1;
@@ -1636,22 +1635,11 @@ static struct dentry *lookup_fast(struct nameidata *nd,
return NULL;
}

- /*
- * This sequence count validates that the inode matches
- * the dentry name information from lookup.
- */
- *inode = d_backing_inode(dentry);
- if (unlikely(read_seqcount_retry(&dentry->d_seq, nd->next_seq)))
- return ERR_PTR(-ECHILD);
-
- /*
+ /*
* This sequence count validates that the parent had no
* changes while we did the lookup of the dentry above.
- *
- * The memory barrier in read_seqcount_begin of child is
- * enough, we can use __read_seqcount_retry here.
*/
- if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq)))
+ if (unlikely(read_seqcount_retry(&parent->d_seq, nd->seq)))
return ERR_PTR(-ECHILD);

status = d_revalidate(dentry, nd->flags);
@@ -1993,7 +1981,6 @@ static const char *handle_dots(struct nameidata *nd, int type)
static const char *walk_component(struct nameidata *nd, int flags)
{
struct dentry *dentry;
- struct inode *inode;
/*
* "." and ".." are special - ".." especially so because it has
* to be able to know about the current root directory and
@@ -2004,7 +1991,7 @@ static const char *walk_component(struct nameidata *nd, int flags)
put_link(nd);
return handle_dots(nd, nd->last_type);
}
- dentry = lookup_fast(nd, &inode);
+ dentry = lookup_fast(nd);
if (IS_ERR(dentry))
return ERR_CAST(dentry);
if (unlikely(!dentry)) {
@@ -3392,7 +3379,6 @@ static const char *open_last_lookups(struct nameidata *nd,
struct dentry *dir = nd->path.dentry;
int open_flag = op->open_flag;
bool got_write = false;
- struct inode *inode;
struct dentry *dentry;
const char *res;

@@ -3408,7 +3394,7 @@ static const char *open_last_lookups(struct nameidata *nd,
if (nd->last.name[nd->last.len])
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
/* we _can_ be in RCU mode here */
- dentry = lookup_fast(nd, &inode);
+ dentry = lookup_fast(nd);
if (IS_ERR(dentry))
return ERR_CAST(dentry);
if (likely(dentry))
--
2.30.2