[RFC][PATCH v2 15/34] fold handle_mounts() into step_into()

Al Viro
2020-02-23T01:20:32Z

The following is true:
* calls of handle_mounts() and step_into() are always
paired in sequences like
err = handle_mounts(nd, dentry, &path, &inode, &seq);
if (unlikely(err < 0))
return err;
err = step_into(nd, &path, flags, inode, seq);
* in all such sequences path is uninitialized before and
unused after this pair of calls
* in all such sequences inode and seq are unused afterwards.

So the call of handle_mounts() can be shifted inside step_into(),
turning 'path' into a local variable in the combined function.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/namei.c | 41 +++++++++++++++--------------------------
1 file changed, 15 insertions(+), 26 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index fe48a8d00ae5..28835ee7168a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1835,31 +1835,35 @@ enum {WALK_FOLLOW = 1, WALK_MORE = 2, WALK_NOFOLLOW = 4};
* so we keep a cache of "no, this doesn't need follow_link"
* for the common case.
*/
-static inline int step_into(struct nameidata *nd, struct path *path,
- int flags, struct inode *inode, unsigned seq)
+static int step_into(struct nameidata *nd, int flags,
+ struct dentry *dentry, struct inode *inode, unsigned seq)
{
+ struct path path;
+ int err = handle_mounts(nd, dentry, &path, &inode, &seq);
+
+ if (err < 0)
+ return err;
if (!(flags & WALK_MORE) && nd->depth)
put_link(nd);
- if (likely(!d_is_symlink(path->dentry)) ||
+ if (likely(!d_is_symlink(path.dentry)) ||
!(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW) ||
flags & WALK_NOFOLLOW) {
/* not a symlink or should not follow */
- path_to_nameidata(path, nd);
+ path_to_nameidata(&path, nd);
nd->inode = inode;
nd->seq = seq;
return 0;
}
/* make sure that d_is_symlink above matches inode */
if (nd->flags & LOOKUP_RCU) {
- if (read_seqcount_retry(&path->dentry->d_seq, seq))
+ if (read_seqcount_retry(&path.dentry->d_seq, seq))
return -ECHILD;
}
- return pick_link(nd, path, inode, seq);
+ return pick_link(nd, &path, inode, seq);
}

static int walk_component(struct nameidata *nd, int flags)
{
- struct path path;
struct dentry *dentry;
struct inode *inode;
unsigned seq;
@@ -1883,11 +1887,7 @@ static int walk_component(struct nameidata *nd, int flags)
if (IS_ERR(dentry))
return PTR_ERR(dentry);
}
-
- err = handle_mounts(nd, dentry, &path, &inode, &seq);
- if (unlikely(err < 0))
- return err;
- return step_into(nd, &path, flags, inode, seq);
+ return step_into(nd, flags, dentry, inode, seq);
}

/*
@@ -2354,17 +2354,10 @@ static inline int lookup_last(struct nameidata *nd)

static int handle_lookup_down(struct nameidata *nd)
{
- struct path path;
- struct inode *inode = nd->inode;
- unsigned seq = nd->seq;
- int err;
-
if (!(nd->flags & LOOKUP_RCU))
dget(nd->path.dentry);
- err = handle_mounts(nd, nd->path.dentry, &path, &inode, &seq);
- if (unlikely(err < 0))
- return err;
- return step_into(nd, &path, WALK_NOFOLLOW, inode, seq);
+ return step_into(nd, WALK_NOFOLLOW,
+ nd->path.dentry, nd->inode, nd->seq);
}

/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
@@ -3283,7 +3276,6 @@ static int do_last(struct nameidata *nd,
int acc_mode = op->acc_mode;
unsigned seq;
struct inode *inode;
- struct path path;
struct dentry *dentry;
int error;

@@ -3382,10 +3374,7 @@ static int do_last(struct nameidata *nd,
}

finish_lookup:
- error = handle_mounts(nd, dentry, &path, &inode, &seq);
- if (unlikely(error < 0))
- return error;
- error = step_into(nd, &path, 0, inode, seq);
+ error = step_into(nd, 0, dentry, inode, seq);
if (unlikely(error))
return error;

--
2.11.0