Revert "autofs4: always use lookup for lookup"

This reverts commit 213614d583748d00967a91cacd656f417efb36ce.

Alas, ->d_revalidate() can't rely on ->lookup() finishing what
it's started; if d_alloc() in do_lookup() fails, we are not going
to call ->lookup() at all.

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

1 files changed, 157 insertions, 317 deletions

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 30cc9ddf4b70..a015b49891df 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -104,99 +104,6 @@ static void autofs4_del_active(struct dentry *dentry)
         return;
 }
 
-static void autofs4_add_rehash_entry(struct autofs_info *ino,
-                                     struct rehash_entry *entry)
-{
-        entry->task = current;
-        INIT_LIST_HEAD(&entry->list);
-        list_add(&entry->list, &ino->rehash_list);
-        return;
-}
-
-static void autofs4_remove_rehash_entry(struct autofs_info *ino)
-{
-        struct list_head *head = &ino->rehash_list;
-        struct rehash_entry *entry;
-        list_for_each_entry(entry, head, list) {
-                if (entry->task == current) {
-                        list_del(&entry->list);
-                        kfree(entry);
-                        break;
-                }
-        }
-        return;
-}
-
-static void autofs4_remove_rehash_entrys(struct autofs_info *ino)
-{
-        struct autofs_sb_info *sbi = ino->sbi;
-        struct rehash_entry *entry, *next;
-        struct list_head *head;
-
-        spin_lock(&sbi->fs_lock);
-        spin_lock(&sbi->lookup_lock);
-        if (!(ino->flags & AUTOFS_INF_REHASH)) {
-                spin_unlock(&sbi->lookup_lock);
-                spin_unlock(&sbi->fs_lock);
-                return;
-        }
-        ino->flags &= ~AUTOFS_INF_REHASH;
-        head = &ino->rehash_list;
-        list_for_each_entry_safe(entry, next, head, list) {
-                list_del(&entry->list);
-                kfree(entry);
-        }
-        spin_unlock(&sbi->lookup_lock);
-        spin_unlock(&sbi->fs_lock);
-        dput(ino->dentry);
-
-        return;
-}
-
-static void autofs4_revalidate_drop(struct dentry *dentry,
-                                    struct rehash_entry *entry)
-{
-        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
-        struct autofs_info *ino = autofs4_dentry_ino(dentry);
-        /*
-         * Add to the active list so we can pick this up in
-         * ->lookup(). Also add an entry to a rehash list so
-         * we know when there are no dentrys in flight so we
-         * know when we can rehash the dentry.
-         */
-        spin_lock(&sbi->lookup_lock);
-        if (list_empty(&ino->active))
-                list_add(&ino->active, &sbi->active_list);
-        autofs4_add_rehash_entry(ino, entry);
-        spin_unlock(&sbi->lookup_lock);
-        if (!(ino->flags & AUTOFS_INF_REHASH)) {
-                ino->flags |= AUTOFS_INF_REHASH;
-                dget(dentry);
-                spin_lock(&dentry->d_lock);
-                __d_drop(dentry);
-                spin_unlock(&dentry->d_lock);
-        }
-        return;
-}
-
-static void autofs4_revalidate_rehash(struct dentry *dentry)
-{
-        struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
-        struct autofs_info *ino = autofs4_dentry_ino(dentry);
-        if (ino->flags & AUTOFS_INF_REHASH) {
-                spin_lock(&sbi->lookup_lock);
-                autofs4_remove_rehash_entry(ino);
-                if (list_empty(&ino->rehash_list)) {
-                        spin_unlock(&sbi->lookup_lock);
-                        ino->flags &= ~AUTOFS_INF_REHASH;
-                        d_rehash(dentry);
-                        dput(ino->dentry);
-                } else
-                        spin_unlock(&sbi->lookup_lock);
-        }
-        return;
-}
-
 static unsigned int autofs4_need_mount(unsigned int flags)
 {
         unsigned int res = 0;
@@ -236,7 +143,7 @@ out:
         return dcache_dir_open(inode, file);
 }
 
-static int try_to_fill_dentry(struct dentry *dentry)
+static int try_to_fill_dentry(struct dentry *dentry, int flags)
 {
         struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
         struct autofs_info *ino = autofs4_dentry_ino(dentry);
@@ -249,17 +156,55 @@ static int try_to_fill_dentry(struct dentry *dentry)
          * Wait for a pending mount, triggering one if there
          * isn't one already
          */
-        DPRINTK("waiting for mount name=%.*s",
-                 dentry->d_name.len, dentry->d_name.name);
+        if (dentry->d_inode == NULL) {
+                DPRINTK("waiting for mount name=%.*s",
+                         dentry->d_name.len, dentry->d_name.name);
 
-        status = autofs4_wait(sbi, dentry, NFY_MOUNT);
+                status = autofs4_wait(sbi, dentry, NFY_MOUNT);
 
-        DPRINTK("mount done status=%d", status);
+                DPRINTK("mount done status=%d", status);
 
-        /* Update expiry counter */
-        ino->last_used = jiffies;
+                /* Turn this into a real negative dentry? */
+                if (status == -ENOENT) {
+                        spin_lock(&sbi->fs_lock);
+                        ino->flags &= ~AUTOFS_INF_PENDING;
+                        spin_unlock(&sbi->fs_lock);
+                        return status;
+                } else if (status) {
+                        /* Return a negative dentry, but leave it "pending" */
+                        return status;
+                }
+        /* Trigger mount for path component or follow link */
+        } else if (ino->flags & AUTOFS_INF_PENDING ||
+                        autofs4_need_mount(flags) ||
+                        current->link_count) {
+                DPRINTK("waiting for mount name=%.*s",
+                        dentry->d_name.len, dentry->d_name.name);
 
-        return status;
+                spin_lock(&sbi->fs_lock);
+                ino->flags |= AUTOFS_INF_PENDING;
+                spin_unlock(&sbi->fs_lock);
+                status = autofs4_wait(sbi, dentry, NFY_MOUNT);
+
+                DPRINTK("mount done status=%d", status);
+
+                if (status) {
+                        spin_lock(&sbi->fs_lock);
+                        ino->flags &= ~AUTOFS_INF_PENDING;
+                        spin_unlock(&sbi->fs_lock);
+                        return status;
+                }
+        }
+
+        /* Initialize expiry counter after successful mount */
+        if (ino)
+                ino->last_used = jiffies;
+
+        spin_lock(&sbi->fs_lock);
+        ino->flags &= ~AUTOFS_INF_PENDING;
+        spin_unlock(&sbi->fs_lock);
+
+        return 0;
 }
 
 /* For autofs direct mounts the follow link triggers the mount */
@@ -313,16 +258,10 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
          */
         if (ino->flags & AUTOFS_INF_PENDING ||
             (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs))) {
-                ino->flags |= AUTOFS_INF_PENDING;
                 spin_unlock(&dcache_lock);
                 spin_unlock(&sbi->fs_lock);
 
-                status = try_to_fill_dentry(dentry);
-
-                spin_lock(&sbi->fs_lock);
-                ino->flags &= ~AUTOFS_INF_PENDING;
-                spin_unlock(&sbi->fs_lock);
-
+                status = try_to_fill_dentry(dentry, 0);
                 if (status)
                         goto out_error;
 
@@ -361,47 +300,18 @@ static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
         struct inode *dir = dentry->d_parent->d_inode;
         struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
-        struct autofs_info *ino = autofs4_dentry_ino(dentry);
-        struct rehash_entry *entry;
+        int oz_mode = autofs4_oz_mode(sbi);
         int flags = nd ? nd->flags : 0;
-        unsigned int mutex_aquired;
+        int status = 1;
 
-        DPRINTK("name = %.*s oz_mode = %d",
-                dentry->d_name.len, dentry->d_name.name, oz_mode);
-
-        /* Daemon never causes a mount to trigger */
-        if (autofs4_oz_mode(sbi))
-                return 1;
-
-        entry = kmalloc(sizeof(struct rehash_entry), GFP_KERNEL);
-        if (!entry)
-                return -ENOMEM;
-
-        mutex_aquired = mutex_trylock(&dir->i_mutex);
-
-        spin_lock(&sbi->fs_lock);
-        spin_lock(&dcache_lock);
         /* Pending dentry */
+        spin_lock(&sbi->fs_lock);
         if (autofs4_ispending(dentry)) {
-                int status;
-
-                /*
-                 * We can only unhash and send this to ->lookup() if
-                 * the directory mutex is held over d_revalidate() and
-                 * ->lookup(). This prevents the VFS from incorrectly
-                 * seeing the dentry as non-existent.
-                 */
-                ino->flags |= AUTOFS_INF_PENDING;
-                if (!mutex_aquired) {
-                        autofs4_revalidate_drop(dentry, entry);
-                        spin_unlock(&dcache_lock);
-                        spin_unlock(&sbi->fs_lock);
-                        return 0;
-                }
-                spin_unlock(&dcache_lock);
+                /* The daemon never causes a mount to trigger */
                 spin_unlock(&sbi->fs_lock);
-                mutex_unlock(&dir->i_mutex);
-                kfree(entry);
+
+                if (oz_mode)
+                        return 1;
 
                 /*
                  * If the directory has gone away due to an expire
@@ -415,82 +325,45 @@ static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
                  * A zero status is success otherwise we have a
                  * negative error code.
                  */
-                status = try_to_fill_dentry(dentry);
-
-                spin_lock(&sbi->fs_lock);
-                ino->flags &= ~AUTOFS_INF_PENDING;
-                spin_unlock(&sbi->fs_lock);
-
+                status = try_to_fill_dentry(dentry, flags);
                 if (status == 0)
                         return 1;
 
                 return status;
         }
+        spin_unlock(&sbi->fs_lock);
+
+        /* Negative dentry.. invalidate if "old" */
+        if (dentry->d_inode == NULL)
+                return 0;
 
         /* Check for a non-mountpoint directory with no contents */
+        spin_lock(&dcache_lock);
         if (S_ISDIR(dentry->d_inode->i_mode) &&
             !d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
                 DPRINTK("dentry=%p %.*s, emptydir",
                          dentry, dentry->d_name.len, dentry->d_name.name);
+                spin_unlock(&dcache_lock);
 
-                if (autofs4_need_mount(flags) || current->link_count) {
-                        int status;
-
-                        /*
-                         * We can only unhash and send this to ->lookup() if
-                         * the directory mutex is held over d_revalidate() and
-                         * ->lookup(). This prevents the VFS from incorrectly
-                         * seeing the dentry as non-existent.
-                         */
-                        ino->flags |= AUTOFS_INF_PENDING;
-                        if (!mutex_aquired) {
-                                autofs4_revalidate_drop(dentry, entry);
-                                spin_unlock(&dcache_lock);
-                                spin_unlock(&sbi->fs_lock);
-                                return 0;
-                        }
-                        spin_unlock(&dcache_lock);
-                        spin_unlock(&sbi->fs_lock);
-                        mutex_unlock(&dir->i_mutex);
-                        kfree(entry);
-
-                        /*
-                         * A zero status is success otherwise we have a
-                         * negative error code.
-                         */
-                        status = try_to_fill_dentry(dentry);
-
-                        spin_lock(&sbi->fs_lock);
-                        ino->flags &= ~AUTOFS_INF_PENDING;
-                        spin_unlock(&sbi->fs_lock);
+                /* The daemon never causes a mount to trigger */
+                if (oz_mode)
+                        return 1;
 
-                        if (status == 0)
-                                return 1;
+                /*
+                 * A zero status is success otherwise we have a
+                 * negative error code.
+                 */
+                status = try_to_fill_dentry(dentry, flags);
+                if (status == 0)
+                        return 1;
 
-                        return status;
-                }
+                return status;
         }
         spin_unlock(&dcache_lock);
-        spin_unlock(&sbi->fs_lock);
-
-        if (mutex_aquired)
-                mutex_unlock(&dir->i_mutex);
-
-        kfree(entry);
 
         return 1;
 }
 
-static void autofs4_free_rehash_entrys(struct autofs_info *inf)
-{
-        struct list_head *head = &inf->rehash_list;
-        struct rehash_entry *entry, *next;
-        list_for_each_entry_safe(entry, next, head, list) {
-                list_del(&entry->list);
-                kfree(entry);
-        }
-}
-
 void autofs4_dentry_release(struct dentry *de)
 {
         struct autofs_info *inf;
@@ -509,8 +382,6 @@ void autofs4_dentry_release(struct dentry *de)
                                 list_del(&inf->active);
                         if (!list_empty(&inf->expiring))
                                 list_del(&inf->expiring);
-                        if (!list_empty(&inf->rehash_list))
-                                autofs4_free_rehash_entrys(inf);
                         spin_unlock(&sbi->lookup_lock);
                 }
 
@@ -543,7 +414,6 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
         const unsigned char *str = name->name;
         struct list_head *p, *head;
 
-restart:
         spin_lock(&dcache_lock);
         spin_lock(&sbi->lookup_lock);
         head = &sbi->active_list;
@@ -561,19 +431,6 @@ restart:
                 if (atomic_read(&active->d_count) == 0)
                         goto next;
 
-                if (active->d_inode && IS_DEADDIR(active->d_inode)) {
-                        if (!list_empty(&ino->rehash_list)) {
-                                dget(active);
-                                spin_unlock(&active->d_lock);
-                                spin_unlock(&sbi->lookup_lock);
-                                spin_unlock(&dcache_lock);
-                                autofs4_remove_rehash_entrys(ino);
-                                dput(active);
-                                goto restart;
-                        }
-                        goto next;
-                }
-
                 qstr = &active->d_name;
 
                 if (active->d_name.hash != hash)
@@ -586,11 +443,13 @@ restart:
                 if (memcmp(qstr->name, str, len))
                         goto next;
 
-                dget(active);
-                spin_unlock(&active->d_lock);
-                spin_unlock(&sbi->lookup_lock);
-                spin_unlock(&dcache_lock);
-                return active;
+                if (d_unhashed(active)) {
+                        dget(active);
+                        spin_unlock(&active->d_lock);
+                        spin_unlock(&sbi->lookup_lock);
+                        spin_unlock(&dcache_lock);
+                        return active;
+                }
 next:
                 spin_unlock(&active->d_lock);
         }
@@ -639,11 +498,13 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
                 if (memcmp(qstr->name, str, len))
                         goto next;
 
-                dget(expiring);
-                spin_unlock(&expiring->d_lock);
-                spin_unlock(&sbi->lookup_lock);
-                spin_unlock(&dcache_lock);
-                return expiring;
+                if (d_unhashed(expiring)) {
+                        dget(expiring);
+                        spin_unlock(&expiring->d_lock);
+                        spin_unlock(&sbi->lookup_lock);
+                        spin_unlock(&dcache_lock);
+                        return expiring;
+                }
 next:
                 spin_unlock(&expiring->d_lock);
         }
@@ -653,48 +514,6 @@ next:
         return NULL;
 }
 
-static struct autofs_info *init_new_dentry(struct autofs_sb_info *sbi,
-                                           struct dentry *dentry, int oz_mode)
-{
-        struct autofs_info *ino;
-
-        /*
-         * Mark the dentry incomplete but don't hash it. We do this
-         * to serialize our inode creation operations (symlink and
-         * mkdir) which prevents deadlock during the callback to
-         * the daemon. Subsequent user space lookups for the same
-         * dentry are placed on the wait queue while the daemon
-         * itself is allowed passage unresticted so the create
-         * operation itself can then hash the dentry. Finally,
-         * we check for the hashed dentry and return the newly
-         * hashed dentry.
-         */
-        dentry->d_op = &autofs4_root_dentry_operations;
-
-        /*
-         * And we need to ensure that the same dentry is used for
-         * all following lookup calls until it is hashed so that
-         * the dentry flags are persistent throughout the request.
-         */
-        ino = autofs4_init_ino(NULL, sbi, 0555);
-        if (!ino)
-                return ERR_PTR(-ENOMEM);
-
-        dentry->d_fsdata = ino;
-        ino->dentry = dentry;
-
-        /*
-         * Only set the mount pending flag for new dentrys not created
-         * by the daemon.
-         */
-        if (!oz_mode)
-                ino->flags |= AUTOFS_INF_PENDING;
-
-        d_instantiate(dentry, NULL);
-
-        return ino;
-}
-
 /* Lookups in the root directory */
 static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 {
@@ -702,7 +521,6 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
         struct autofs_info *ino;
         struct dentry *expiring, *active;
         int oz_mode;
-        int status = 0;
 
         DPRINTK("name = %.*s",
                 dentry->d_name.len, dentry->d_name.name);
@@ -717,26 +535,44 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
         DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
                  current->pid, task_pgrp_nr(current), sbi->catatonic, oz_mode);
 
-        spin_lock(&sbi->fs_lock);
         active = autofs4_lookup_active(dentry);
         if (active) {
                 dentry = active;
                 ino = autofs4_dentry_ino(dentry);
-                /* If this came from revalidate, rehash it */
-                autofs4_revalidate_rehash(dentry);
-                spin_unlock(&sbi->fs_lock);
         } else {
-                spin_unlock(&sbi->fs_lock);
-                ino = init_new_dentry(sbi, dentry, oz_mode);
-                if (IS_ERR(ino))
-                        return (struct dentry *) ino;
-        }
+                /*
+                 * Mark the dentry incomplete but don't hash it. We do this
+                 * to serialize our inode creation operations (symlink and
+                 * mkdir) which prevents deadlock during the callback to
+                 * the daemon. Subsequent user space lookups for the same
+                 * dentry are placed on the wait queue while the daemon
+                 * itself is allowed passage unresticted so the create
+                 * operation itself can then hash the dentry. Finally,
+                 * we check for the hashed dentry and return the newly
+                 * hashed dentry.
+                 */
+                dentry->d_op = &autofs4_root_dentry_operations;
+
+                /*
+                 * And we need to ensure that the same dentry is used for
+                 * all following lookup calls until it is hashed so that
+                 * the dentry flags are persistent throughout the request.
+                 */
+                ino = autofs4_init_ino(NULL, sbi, 0555);
+                if (!ino)
+                        return ERR_PTR(-ENOMEM);
 
-        autofs4_add_active(dentry);
+                dentry->d_fsdata = ino;
+                ino->dentry = dentry;
+
+                autofs4_add_active(dentry);
+
+                d_instantiate(dentry, NULL);
+        }
 
         if (!oz_mode) {
-                expiring = autofs4_lookup_expiring(dentry);
                 mutex_unlock(&dir->i_mutex);
+                expiring = autofs4_lookup_expiring(dentry);
                 if (expiring) {
                         /*
                          * If we are racing with expire the request might not
@@ -744,22 +580,23 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
                          * so it must have been successful, so just wait for it.
                          */
                         autofs4_expire_wait(expiring);
+                        autofs4_del_expiring(expiring);
                         dput(expiring);
                 }
-                status = try_to_fill_dentry(dentry);
-                mutex_lock(&dir->i_mutex);
+
                 spin_lock(&sbi->fs_lock);
-                ino->flags &= ~AUTOFS_INF_PENDING;
+                ino->flags |= AUTOFS_INF_PENDING;
                 spin_unlock(&sbi->fs_lock);
+                if (dentry->d_op && dentry->d_op->d_revalidate)
+                        (dentry->d_op->d_revalidate)(dentry, nd);
+                mutex_lock(&dir->i_mutex);
         }
 
-        autofs4_del_active(dentry);
-
         /*
-         * If we had a mount fail, check if we had to handle
+         * If we are still pending, check if we had to handle
          * a signal. If so we can force a restart..
          */
-        if (status) {
+        if (ino->flags & AUTOFS_INF_PENDING) {
                 /* See if we were interrupted */
                 if (signal_pending(current)) {
                         sigset_t *sigset = &current->pending.signal;
@@ -771,46 +608,43 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
                             return ERR_PTR(-ERESTARTNOINTR);
                         }
                 }
-        }
-
-        /*
-         * User space can (and has done in the past) remove and re-create
-         * this directory during the callback. This can leave us with an
-         * unhashed dentry, but a successful mount!  So we need to
-         * perform another cached lookup in case the dentry now exists.
-         */
-        if (!oz_mode && !have_submounts(dentry)) {
-                struct dentry *new;
-                new = d_lookup(dentry->d_parent, &dentry->d_name);
-                if (new) {
-                        if (active)
-                                dput(active);
-                        return new;
-                } else {
-                        if (!status)
-                                status = -ENOENT;
+                if (!oz_mode) {
+                        spin_lock(&sbi->fs_lock);
+                        ino->flags &= ~AUTOFS_INF_PENDING;
+                        spin_unlock(&sbi->fs_lock);
                 }
         }
 
         /*
-         * If we had a mount failure, return status to user space.
-         * If the mount succeeded and we used a dentry from the active queue
-         * return it.
+         * If this dentry is unhashed, then we shouldn't honour this
+         * lookup.  Returning ENOENT here doesn't do the right thing
+         * for all system calls, but it should be OK for the operations
+         * we permit from an autofs.
          */
-        if (status) {
-                dentry = ERR_PTR(status);
-                if (active)
-                        dput(active);
-                return dentry;
-        } else {
+        if (!oz_mode && d_unhashed(dentry)) {
                 /*
-                 * Valid successful mount, return active dentry or NULL
-                 * for a new dentry.
+                 * A user space application can (and has done in the past)
+                 * remove and re-create this directory during the callback.
+                 * This can leave us with an unhashed dentry, but a
+                 * successful mount!  So we need to perform another
+                 * cached lookup in case the dentry now exists.
                  */
+                struct dentry *parent = dentry->d_parent;
+                struct dentry *new = d_lookup(parent, &dentry->d_name);
+                if (new != NULL)
+                        dentry = new;
+                else
+                        dentry = ERR_PTR(-ENOENT);
+
                 if (active)
-                        return active;
+                        dput(active);
+
+                return dentry;
         }
 
+        if (active)
+                return active;
+
         return NULL;
 }
 
@@ -834,6 +668,8 @@ static int autofs4_dir_symlink(struct inode *dir,
         if (!ino)
                 return -ENOMEM;
 
+        autofs4_del_active(dentry);
+
         ino->size = strlen(symname);
         cp = kmalloc(ino->size + 1, GFP_KERNEL);
         if (!cp) {
@@ -910,6 +746,7 @@ static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
         dir->i_mtime = CURRENT_TIME;
 
         spin_lock(&dcache_lock);
+        autofs4_add_expiring(dentry);
         spin_lock(&dentry->d_lock);
         __d_drop(dentry);
         spin_unlock(&dentry->d_lock);
@@ -935,6 +772,7 @@ static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
                 spin_unlock(&dcache_lock);
                 return -ENOTEMPTY;
         }
+        autofs4_add_expiring(dentry);
         spin_lock(&dentry->d_lock);
         __d_drop(dentry);
         spin_unlock(&dentry->d_lock);
@@ -972,6 +810,8 @@ static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
         if (!ino)
                 return -ENOMEM;
 
+        autofs4_del_active(dentry);
+
         inode = autofs4_get_inode(dir->i_sb, ino);
         if (!inode) {
                 if (!dentry->d_fsdata)