autofs4: Add d_manage() dentry operation

This patch required a previous patch to add the ->d_automount()
dentry operation.

Add a function to use the newly defined ->d_manage() dentry operation
for blocking during mount and expire.

Whether the VFS calls the dentry operations d_automount() and d_manage()
is controled by the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags. autofs
uses the d_automount() operation to callback to user space to request
mount operations and the d_manage() operation to block walks into mounts
that are under construction or destruction.

In order to prevent these functions from being called unnecessarily the
DMANAGED_* flags are cleared for cases which would cause this. In the
common case the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags are both
set for dentrys waiting to be mounted. The DMANAGED_TRANSIT flag is
cleared upon successful mount request completion and set during expire
runs, both during the dentry expire check, and if selected for expire,
is left set until a subsequent successful mount request completes.

The exception to this is the so-called rootless multi-mount which has
no actual mount at its base. In this case the DMANAGED_AUTOMOUNT flag
is cleared upon successful mount request completion as well and set
again after a successful expire.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 26 insertions, 25 deletions

diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 0571ec8352b7..3ed79d76c233 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -26,10 +26,6 @@ static inline int autofs4_can_expire(struct dentry *dentry,
         if (ino == NULL)
                 return 0;
 
-        /* No point expiring a pending mount */
-        if (ino->flags & AUTOFS_INF_PENDING)
-                return 0;
-
         if (!do_now) {
                 /* Too young to die */
                 if (!timeout || time_after(ino->last_used + timeout, now))
@@ -283,6 +279,7 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
         unsigned long timeout;
         struct dentry *root = dget(sb->s_root);
         int do_now = how & AUTOFS_EXP_IMMEDIATE;
+        struct autofs_info *ino;
 
         if (!root)
                 return NULL;
@@ -291,20 +288,21 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
         timeout = sbi->exp_timeout;
 
         spin_lock(&sbi->fs_lock);
+        ino = autofs4_dentry_ino(root);
+        /* No point expiring a pending mount */
+        if (ino->flags & AUTOFS_INF_PENDING) {
+                spin_unlock(&sbi->fs_lock);
+                return NULL;
+        }
+        managed_dentry_set_transit(root);
         if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
                 struct autofs_info *ino = autofs4_dentry_ino(root);
-                if (d_mountpoint(root)) {
-                        ino->flags |= AUTOFS_INF_MOUNTPOINT;
-                        spin_lock(&root->d_lock);
-                        root->d_flags &= ~DCACHE_MOUNTED;
-                        spin_unlock(&root->d_lock);
-                }
                 ino->flags |= AUTOFS_INF_EXPIRING;
-                managed_dentry_set_automount(root);
                 init_completion(&ino->expire_complete);
                 spin_unlock(&sbi->fs_lock);
                 return root;
         }
+        managed_dentry_clear_transit(root);
         spin_unlock(&sbi->fs_lock);
         dput(root);
 
@@ -341,6 +339,10 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
         while ((dentry = get_next_positive_dentry(dentry, root))) {
                 spin_lock(&sbi->fs_lock);
                 ino = autofs4_dentry_ino(dentry);
+                /* No point expiring a pending mount */
+                if (ino->flags & AUTOFS_INF_PENDING)
+                        goto cont;
+                managed_dentry_set_transit(dentry);
 
                 /*
                  * Case 1: (i) indirect mount or top level pseudo direct mount
@@ -400,6 +402,8 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
                         }
                 }
 next:
+                managed_dentry_clear_transit(dentry);
+cont:
                 spin_unlock(&sbi->fs_lock);
         }
         return NULL;
@@ -409,7 +413,6 @@ found:
                 expired, (int)expired->d_name.len, expired->d_name.name);
         ino = autofs4_dentry_ino(expired);
         ino->flags |= AUTOFS_INF_EXPIRING;
-        managed_dentry_set_automount(expired);
         init_completion(&ino->expire_complete);
         spin_unlock(&sbi->fs_lock);
         spin_lock(&autofs4_lock);
@@ -482,7 +485,7 @@ int autofs4_expire_run(struct super_block *sb,
         ino = autofs4_dentry_ino(dentry);
         ino->flags &= ~AUTOFS_INF_EXPIRING;
         if (!d_unhashed(dentry))
-                managed_dentry_clear_automount(dentry);
+                managed_dentry_clear_transit(dentry);
         complete_all(&ino->expire_complete);
         spin_unlock(&sbi->fs_lock);
 
@@ -508,20 +511,18 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
                 ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
 
                 spin_lock(&sbi->fs_lock);
-                if (ino->flags & AUTOFS_INF_MOUNTPOINT) {
-                        spin_lock(&sb->s_root->d_lock);
-                        /*
-                         * If we haven't been expired away, then reset
-                         * mounted status.
-                         */
-                        if (mnt->mnt_parent != mnt)
-                                sb->s_root->d_flags |= DCACHE_MOUNTED;
-                        spin_unlock(&sb->s_root->d_lock);
-                        ino->flags &= ~AUTOFS_INF_MOUNTPOINT;
-                }
                 ino->flags &= ~AUTOFS_INF_EXPIRING;
+                spin_lock(&dentry->d_lock);
                 if (ret)
-                        managed_dentry_clear_automount(dentry);
+                        __managed_dentry_clear_transit(dentry);
+                else {
+                        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);