handle_mounts(): start building a sane wrapper for follow_managed()

All callers of follow_managed() follow it on success with the same steps -
d_backing_inode(path->dentry) is calculated and stored into some struct inode *
variable and, in all but one case, an unsigned variable (nd->seq to be) is
zeroed.  The single exception is lookup_fast() and there zeroing is correct
thing to do - not doing it is a pointless microoptimization.

	Add a wrapper for follow_managed() that would do that combination.
It's mostly a vehicle for code massage - it will be changing quite a bit,
and the current calling conventions are by no means final.  Right now it
takes path, nameidata and (as out params) inode and seq, similar to
__follow_mount_rcu().  Which will soon get folded into it...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/namei.c b/fs/namei.c
index 6938d20aa73a12b694fbf51556a0f0046f4541a4..c104ec75faef915f80c26f7c48fd69fca585c02d 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1385,6 +1385,18 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
                !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
 }
 
+static inline int handle_mounts(struct path *path, struct nameidata *nd,
+                         struct inode **inode, unsigned int *seqp)
+{
+       int ret = follow_managed(path, nd);
+
+       if (likely(ret >= 0)) {
+               *inode = d_backing_inode(path->dentry);
+               *seqp = 0; /* out of RCU mode, so the value doesn't matter */
+       }
+       return ret;
+}
+
 static int follow_dotdot_rcu(struct nameidata *nd)
 {
        struct inode *inode = nd->inode;
@@ -1607,7 +1619,6 @@ static int lookup_fast(struct nameidata *nd,
        struct vfsmount *mnt = nd->path.mnt;
        struct dentry *dentry, *parent = nd->path.dentry;
        int status = 1;
-       int err;
 
        /*
         * Rename seqlock is not required here because in the off chance
@@ -1677,10 +1688,7 @@ static int lookup_fast(struct nameidata *nd,
 
        path->mnt = mnt;
        path->dentry = dentry;
-       err = follow_managed(path, nd);
-       if (likely(err > 0))
-               *inode = d_backing_inode(path->dentry);
-       return err;
+       return handle_mounts(path, nd, inode, seqp);
 }
 
 /* Fast lookup failed, do it the slow way */
@@ -1875,12 +1883,9 @@ static int walk_component(struct nameidata *nd, int flags)
                        return PTR_ERR(path.dentry);
 
                path.mnt = nd->path.mnt;
-               err = follow_managed(&path, nd);
+               err = handle_mounts(&path, nd, &inode, &seq);
                if (unlikely(err < 0))
                        return err;
-
-               seq = 0;        /* we are already out of RCU mode */
-               inode = d_backing_inode(path.dentry);
        }
 
        return step_into(nd, &path, flags, inode, seq);
@@ -2365,11 +2370,9 @@ static int handle_lookup_down(struct nameidata *nd)
                        return -ECHILD;
        } else {
                dget(path.dentry);
-               err = follow_managed(&path, nd);
+               err = handle_mounts(&path, nd, &inode, &seq);
                if (unlikely(err < 0))
                        return err;
-               inode = d_backing_inode(path.dentry);
-               seq = 0;
        }
        path_to_nameidata(&path, nd);
        nd->inode = inode;
@@ -3392,12 +3395,9 @@ static int do_last(struct nameidata *nd,
                got_write = false;
        }
 
-       error = follow_managed(&path, nd);
+       error = handle_mounts(&path, nd, &inode, &seq);
        if (unlikely(error < 0))
                return error;
-
-       seq = 0;        /* out of RCU mode, so the value doesn't matter */
-       inode = d_backing_inode(path.dentry);
 finish_lookup:
        error = step_into(nd, &path, 0, inode, seq);
        if (unlikely(error))