autofs4 - dont clear DCACHE_NEED_AUTOMOUNT on rootless mount

The DCACHE_NEED_AUTOMOUNT flag is cleared on mount and set on expire
for autofs rootless multi-mount dentrys to prevent unnecessary calls
to ->d_automount().

Since DCACHE_MANAGE_TRANSIT is always set on autofs dentrys ->d_managed()
is always called so the check can be done in ->d_manage() without the
need to change the flag. This still avoids unnecessary calls to
->d_automount(), adds negligible overhead and eliminates a seriously
ugly check in the expire code.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 842d00048a652f8cb9ebda7eeea40d62e9cb6720..01443ce43ee75f072158afbc313a6e206bb2f10d 100644 (file)
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -548,15 +548,6 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 
                spin_lock(&sbi->fs_lock);
                ino->flags &= ~AUTOFS_INF_EXPIRING;
-               spin_lock(&dentry->d_lock);
-               if (!ret) {
-                       if ((IS_ROOT(dentry) ||
-                           (autofs_type_indirect(sbi->type) &&
-                            IS_ROOT(dentry->d_parent))) &&
-                           !(dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
-                               __managed_dentry_set_automount(dentry);
-               }
-               spin_unlock(&dentry->d_lock);
                complete_all(&ino->expire_complete);
                spin_unlock(&sbi->fs_lock);
                dput(dentry);

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 91b11650722e517e2066219fac803aefdae78470..30a6ab66e99af11ddd39fa9e804a72543fccb2a0 100644 (file)
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -355,7 +355,6 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
                status = autofs4_mount_wait(dentry);
                if (status)
                        return ERR_PTR(status);
-               spin_lock(&sbi->fs_lock);
                goto done;
        }
 
@@ -364,8 +363,11 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
         * having d_mountpoint() true, so there's no need to call back
         * to the daemon.
         */
-       if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode))
+       if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {
+               spin_unlock(&sbi->fs_lock);
                goto done;
+       }
+
        if (!d_mountpoint(dentry)) {
                /*
                 * It's possible that user space hasn't removed directories
@@ -379,8 +381,10 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
                 * require user space behave.
                 */
                if (sbi->version > 4) {
-                       if (have_submounts(dentry))
+                       if (have_submounts(dentry)) {
+                               spin_unlock(&sbi->fs_lock);
                                goto done;
+                       }
                } else {
                        spin_lock(&dentry->d_lock);
                        if (!list_empty(&dentry->d_subdirs)) {
@@ -399,28 +403,8 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
                        return ERR_PTR(status);
                }
        }
-done:
-       if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
-               /*
-                * Any needed mounting has been completed and the path
-                * updated so clear DCACHE_NEED_AUTOMOUNT so we don't
-                * call ->d_automount() on rootless multi-mounts since
-                * it can lead to an incorrect ELOOP error return.
-                *
-                * Only clear DMANAGED_AUTOMOUNT for rootless multi-mounts and
-                * symlinks as in all other cases the dentry will be covered by
-                * an actual mount so ->d_automount() won't be called during
-                * the follow.
-                */
-               spin_lock(&dentry->d_lock);
-               if ((!d_mountpoint(dentry) &&
-                   !list_empty(&dentry->d_subdirs)) ||
-                   (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)))
-                       __managed_dentry_clear_automount(dentry);
-               spin_unlock(&dentry->d_lock);
-       }
        spin_unlock(&sbi->fs_lock);
-
+done:
        /* Mount succeeded, check if we ended up with a new dentry */
        dentry = autofs4_mountpoint_changed(path);
        if (!dentry)
@@ -432,6 +416,8 @@ done:
 int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
 {
        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
+       struct autofs_info *ino = autofs4_dentry_ino(dentry);
+       int status;
 
        DPRINTK("dentry=%p %.*s",
                dentry, dentry->d_name.len, dentry->d_name.name);
@@ -456,7 +442,32 @@ int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
         * This dentry may be under construction so wait on mount
         * completion.
         */
-       return autofs4_mount_wait(dentry);
+       status = autofs4_mount_wait(dentry);
+       if (status)
+               return status;
+
+       spin_lock(&sbi->fs_lock);
+       /*
+        * If the dentry has been selected for expire while we slept
+        * on the lock then it might go away. We'll deal with that in
+        * ->d_automount() and wait on a new mount if the expire
+        * succeeds or return here if it doesn't (since there's no
+        * mount to follow with a rootless multi-mount).
+        */
+       if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
+               /*
+                * Any needed mounting has been completed and the path
+                * updated so check if this is a rootless multi-mount so
+                * we can avoid needless calls ->d_automount() and avoid
+                * an incorrect ELOOP error return.
+                */
+               if ((!d_mountpoint(dentry) && !simple_empty(dentry)) ||
+                   (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)))
+                       status = -EISDIR;
+       }
+       spin_unlock(&sbi->fs_lock);
+
+       return status;
 }
 
 /* Lookups in the root directory */