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>

diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 1ebfe53..f0c95e0 100644 (file)
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -99,7 +99,6 @@ struct autofs_info {
 };
 
 #define AUTOFS_INF_EXPIRING    (1<<0) /* dentry is in the process of expiring */
-#define AUTOFS_INF_MOUNTPOINT  (1<<1) /* mountpoint status for direct expire */
 #define AUTOFS_INF_PENDING     (1<<2) /* dentry pending mount */
 
 struct autofs_wait_queue {
@@ -221,6 +220,7 @@ extern const struct file_operations autofs4_root_operations;
 /* Operations methods */
 
 struct vfsmount *autofs4_d_automount(struct path *);
+int autofs4_d_manage(struct dentry *, bool);
 
 /* VFS automount flags management functions */
 
@@ -248,6 +248,54 @@ static inline void managed_dentry_clear_automount(struct dentry *dentry)
        spin_unlock(&dentry->d_lock);
 }
 
+static inline void __managed_dentry_set_transit(struct dentry *dentry)
+{
+       dentry->d_flags |= DCACHE_MANAGE_TRANSIT;
+}
+
+static inline void managed_dentry_set_transit(struct dentry *dentry)
+{
+       spin_lock(&dentry->d_lock);
+       __managed_dentry_set_transit(dentry);
+       spin_unlock(&dentry->d_lock);
+}
+
+static inline void __managed_dentry_clear_transit(struct dentry *dentry)
+{
+       dentry->d_flags &= ~DCACHE_MANAGE_TRANSIT;
+}
+
+static inline void managed_dentry_clear_transit(struct dentry *dentry)
+{
+       spin_lock(&dentry->d_lock);
+       __managed_dentry_clear_transit(dentry);
+       spin_unlock(&dentry->d_lock);
+}
+
+static inline void __managed_dentry_set_managed(struct dentry *dentry)
+{
+       dentry->d_flags |= (DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT);
+}
+
+static inline void managed_dentry_set_managed(struct dentry *dentry)
+{
+       spin_lock(&dentry->d_lock);
+       __managed_dentry_set_managed(dentry);
+       spin_unlock(&dentry->d_lock);
+}
+
+static inline void __managed_dentry_clear_managed(struct dentry *dentry)
+{
+       dentry->d_flags &= ~(DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT);
+}
+
+static inline void managed_dentry_clear_managed(struct dentry *dentry)
+{
+       spin_lock(&dentry->d_lock);
+       __managed_dentry_clear_managed(dentry);
+       spin_unlock(&dentry->d_lock);
+}
+
 /* Initializing function */
 
 int autofs4_fill_super(struct super_block *, void *, int);

diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 0571ec8..3ed79d7 100644 (file)
--- 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);

diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
index d0aa38c..75c1ed8 100644 (file)
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -253,6 +253,7 @@ static struct autofs_info *autofs4_mkroot(struct autofs_sb_info *sbi)
 
 static const struct dentry_operations autofs4_sb_dentry_operations = {
        .d_automount    = autofs4_d_automount,
+       .d_manage       = autofs4_d_manage,
        .d_release      = autofs4_dentry_release,
 };
 
@@ -322,7 +323,7 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
        }
 
        if (autofs_type_trigger(sbi->type))
-               __managed_dentry_set_automount(root);
+               __managed_dentry_set_managed(root);
 
        root_inode->i_fop = &autofs4_root_operations;
        root_inode->i_op = autofs_type_trigger(sbi->type) ?

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 27dc53e..f1076b9 100644 (file)
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -424,6 +424,7 @@ static const struct dentry_operations autofs4_root_dentry_operations = {
 /* For other dentries */
 static const struct dentry_operations autofs4_dentry_operations = {
        .d_automount    = autofs4_d_automount,
+       .d_manage       = autofs4_d_manage,
        .d_release      = autofs4_dentry_release,
 };
 
@@ -604,6 +605,18 @@ struct vfsmount *autofs4_d_automount(struct path *path)
        DPRINTK("dentry=%p %.*s",
                dentry, dentry->d_name.len, dentry->d_name.name);
 
+       /*
+        * Someone may have manually umounted this or it was a submount
+        * that has gone away.
+        */
+       spin_lock(&dentry->d_lock);
+       if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
+               if (!(dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
+                    (dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
+                       __managed_dentry_set_transit(path->dentry);
+       }
+       spin_unlock(&dentry->d_lock);
+
        /* The daemon never triggers a mount. */
        if (autofs4_oz_mode(sbi))
                return NULL;
@@ -633,31 +646,63 @@ struct vfsmount *autofs4_d_automount(struct path *path)
 
        /*
         * If the dentry is a symlink it's equivalent to a directory
-        * having d_mounted() true, so there's no need to call back
+        * 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))
                goto done;
-       spin_lock(&dentry->d_lock);
-       if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
+       if (!d_mountpoint(dentry)) {
+               /*
+                * It's possible that user space hasn't removed directories
+                * after umounting a rootless multi-mount, although it
+                * should. For v5 have_submounts() is sufficient to handle
+                * this because the leaves of the directory tree under the
+                * mount never trigger mounts themselves (they have an autofs
+                * trigger mount mounted on them). But v4 pseudo direct mounts
+                * do need the leaves to to trigger mounts. In this case we
+                * have no choice but to use the list_empty() check and
+                * require user space behave.
+                */
+               if (sbi->version > 4) {
+                       if (have_submounts(dentry))
+                               goto done;
+               } else {
+                       spin_lock(&dentry->d_lock);
+                       if (!list_empty(&dentry->d_subdirs)) {
+                               spin_unlock(&dentry->d_lock);
+                               goto done;
+                       }
+                       spin_unlock(&dentry->d_lock);
+               }
                ino->flags |= AUTOFS_INF_PENDING;
-               spin_unlock(&dentry->d_lock);
                spin_unlock(&sbi->fs_lock);
                status = autofs4_mount_wait(dentry);
                if (status)
                        return ERR_PTR(status);
                spin_lock(&sbi->fs_lock);
                ino->flags &= ~AUTOFS_INF_PENDING;
-               goto done;
        }
-       spin_unlock(&dentry->d_lock);
 done:
-       /*
-        * Any needed mounting has been completed and the path updated
-        * so turn this into a normal dentry so we don't continually
-        * call ->d_automount().
-        */
-       managed_dentry_clear_automount(dentry);
+       if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
+               /*
+                * Any needed mounting has been completed and the path updated
+                * so turn this into a normal dentry so we don't continually
+                * call ->d_automount() and ->d_manage().
+                */
+               spin_lock(&dentry->d_lock);
+               __managed_dentry_clear_transit(dentry);
+               /*
+                * 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.
+                */
+               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);
 
        /* Mount succeeded, check if we ended up with a new dentry */
@@ -668,6 +713,30 @@ done:
        return NULL;
 }
 
+int autofs4_d_manage(struct dentry *dentry, bool mounting_here)
+{
+       struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
+
+       DPRINTK("dentry=%p %.*s",
+               dentry, dentry->d_name.len, dentry->d_name.name);
+
+       /* The daemon never waits. */
+       if (autofs4_oz_mode(sbi) || mounting_here) {
+               if (!d_mountpoint(dentry))
+                       return -EISDIR;
+               return 0;
+       }
+
+       /* Wait for pending expires */
+       do_expire_wait(dentry);
+
+       /*
+        * This dentry may be under construction so wait on mount
+        * completion.
+        */
+       return autofs4_mount_wait(dentry);
+}
+
 /* Lookups in the root directory */
 static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 {
@@ -704,7 +773,7 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
                /* Mark entries in the root as mount triggers */
                if (autofs_type_indirect(sbi->type) && IS_ROOT(dentry->d_parent)) {
                        d_set_d_op(dentry, &autofs4_dentry_operations);
-                       managed_dentry_set_automount(dentry);
+                       __managed_dentry_set_managed(dentry);
                }
 
                ino = autofs4_init_ino(NULL, sbi, 0555);