[RFC PATCH 11/11] autofs4 - always use lookup for lookup

From: Ian Kent
Date: Thu Sep 24 2009 - 04:32:09 EST

We need to be able to cope with the directory mutex being held during
->d_revalidate() in some cases, but not all cases, and not necessarily
by us. Because we need to release the mutex when we call back to the
daemon to do perform a mount we must be sure that it is us who holds
the mutex so we must redirect mount requests to ->lookup() if the mutex
is held.

Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
---

fs/autofs4/autofs_i.h | 7 +
fs/autofs4/expire.c | 6 +
fs/autofs4/inode.c | 1
fs/autofs4/root.c | 474 +++++++++++++++++++++++++++++++++----------------
4 files changed, 330 insertions(+), 158 deletions(-)

diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 3d283ab..0118d67 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -60,6 +60,11 @@ do { \
current->pid, __func__, ##args); \
} while (0)

+struct rehash_entry {
+ struct task_struct *task;
+ struct list_head list;
+};
+
/* Unified info structure. This is pointed to by both the dentry and
inode structures. Each file in the filesystem has an instance of this
structure. It holds a reference to the dentry, so dentries are never
@@ -76,6 +81,7 @@ struct autofs_info {

struct list_head active;
int active_count;
+ struct list_head rehash_list;

struct list_head expiring;

@@ -98,6 +104,7 @@ 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 */
+#define AUTOFS_INF_REHASH (1<<3) /* dentry in transit to ->lookup() */

struct autofs_wait_queue {
wait_queue_head_t queue;
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index a796c94..74bc9aa 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -279,6 +279,7 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
root->d_mounted--;
}
ino->flags |= AUTOFS_INF_EXPIRING;
+ autofs4_add_expiring(root);
init_completion(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
return root;
@@ -406,6 +407,7 @@ found:
expired, (int)expired->d_name.len, expired->d_name.name);
ino = autofs4_dentry_ino(expired);
ino->flags |= AUTOFS_INF_EXPIRING;
+ autofs4_add_expiring(expired);
init_completion(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
spin_lock(&dcache_lock);
@@ -433,7 +435,7 @@ int autofs4_expire_wait(struct dentry *dentry)

DPRINTK("expire done status=%d", status);

- if (d_unhashed(dentry))
+ if (d_unhashed(dentry) && IS_DEADDIR(dentry->d_inode))
return -EAGAIN;

return status;
@@ -473,6 +475,7 @@ int autofs4_expire_run(struct super_block *sb,
spin_lock(&sbi->fs_lock);
ino = autofs4_dentry_ino(dentry);
ino->flags &= ~AUTOFS_INF_EXPIRING;
+ autofs4_del_expiring(dentry);
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);

@@ -503,6 +506,7 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
ino->flags &= ~AUTOFS_INF_MOUNTPOINT;
}
ino->flags &= ~AUTOFS_INF_EXPIRING;
+ autofs4_del_expiring(dentry);
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 4670a78..d0a3de2 100644
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -49,6 +49,7 @@ struct autofs_info *autofs4_init_ino(struct autofs_info *ino,
ino->dentry = NULL;
ino->size = 0;
INIT_LIST_HEAD(&ino->active);
+ INIT_LIST_HEAD(&ino->rehash_list);
ino->active_count = 0;
INIT_LIST_HEAD(&ino->expiring);
atomic_set(&ino->count, 0);
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index a015b49..30cc9dd 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -104,6 +104,99 @@ 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;
@@ -143,7 +236,7 @@ out:
return dcache_dir_open(inode, file);
}

-static int try_to_fill_dentry(struct dentry *dentry, int flags)
+static int try_to_fill_dentry(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
struct autofs_info *ino = autofs4_dentry_ino(dentry);
@@ -156,55 +249,17 @@ static int try_to_fill_dentry(struct dentry *dentry, int flags)
* Wait for a pending mount, triggering one if there
* isn't one already
*/
- if (dentry->d_inode == NULL) {
- DPRINTK("waiting for mount name=%.*s",
- dentry->d_name.len, dentry->d_name.name);
+ 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);
-
- /* 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);
+ DPRINTK("mount done status=%d", status);

- spin_lock(&sbi->fs_lock);
- ino->flags |= AUTOFS_INF_PENDING;
- spin_unlock(&sbi->fs_lock);
- status = autofs4_wait(sbi, dentry, NFY_MOUNT);
+ /* Update expiry counter */
+ ino->last_used = jiffies;

- 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;
+ return status;
}

/* For autofs direct mounts the follow link triggers the mount */
@@ -258,10 +313,16 @@ 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, 0);
+ status = try_to_fill_dentry(dentry);
+
+ spin_lock(&sbi->fs_lock);
+ ino->flags &= ~AUTOFS_INF_PENDING;
+ spin_unlock(&sbi->fs_lock);
+
if (status)
goto out_error;

@@ -300,18 +361,47 @@ 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);
- int oz_mode = autofs4_oz_mode(sbi);
+ struct autofs_info *ino = autofs4_dentry_ino(dentry);
+ struct rehash_entry *entry;
int flags = nd ? nd->flags : 0;
- int status = 1;
+ unsigned int mutex_aquired;
+
+ 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);

- /* Pending dentry */
spin_lock(&sbi->fs_lock);
+ spin_lock(&dcache_lock);
+ /* Pending dentry */
if (autofs4_ispending(dentry)) {
- /* The daemon never causes a mount to trigger */
- spin_unlock(&sbi->fs_lock);
+ int status;

- if (oz_mode)
- return 1;
+ /*
+ * 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);

/*
* If the directory has gone away due to an expire
@@ -325,45 +415,82 @@ 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, flags);
+ status = try_to_fill_dentry(dentry);
+
+ spin_lock(&sbi->fs_lock);
+ ino->flags &= ~AUTOFS_INF_PENDING;
+ spin_unlock(&sbi->fs_lock);
+
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);

- /* The daemon never causes a mount to trigger */
- if (oz_mode)
- return 1;
+ if (autofs4_need_mount(flags) || current->link_count) {
+ int status;

- /*
- * A zero status is success otherwise we have a
- * negative error code.
- */
- status = try_to_fill_dentry(dentry, flags);
- if (status == 0)
- return 1;
+ /*
+ * 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);

- return status;
+ /*
+ * 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);
+
+ if (status == 0)
+ return 1;
+
+ 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;
@@ -382,6 +509,8 @@ 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);
}

@@ -414,6 +543,7 @@ 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;
@@ -431,6 +561,19 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
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)
@@ -443,13 +586,11 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
if (memcmp(qstr->name, str, len))
goto next;

- if (d_unhashed(active)) {
- dget(active);
- spin_unlock(&active->d_lock);
- spin_unlock(&sbi->lookup_lock);
- spin_unlock(&dcache_lock);
- return 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);
}
@@ -498,13 +639,11 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
if (memcmp(qstr->name, str, len))
goto next;

- if (d_unhashed(expiring)) {
- dget(expiring);
- spin_unlock(&expiring->d_lock);
- spin_unlock(&sbi->lookup_lock);
- spin_unlock(&dcache_lock);
- return 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);
}
@@ -514,6 +653,48 @@ 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)
{
@@ -521,6 +702,7 @@ 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);
@@ -535,44 +717,26 @@ 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 {
- /*
- * 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;
-
- autofs4_add_active(dentry);
-
- d_instantiate(dentry, NULL);
+ spin_unlock(&sbi->fs_lock);
+ ino = init_new_dentry(sbi, dentry, oz_mode);
+ if (IS_ERR(ino))
+ return (struct dentry *) ino;
}

+ autofs4_add_active(dentry);
+
if (!oz_mode) {
- mutex_unlock(&dir->i_mutex);
expiring = autofs4_lookup_expiring(dentry);
+ mutex_unlock(&dir->i_mutex);
if (expiring) {
/*
* If we are racing with expire the request might not
@@ -580,23 +744,22 @@ 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 are still pending, check if we had to handle
+ * If we had a mount fail, check if we had to handle
* a signal. If so we can force a restart..
*/
- if (ino->flags & AUTOFS_INF_PENDING) {
+ if (status) {
/* See if we were interrupted */
if (signal_pending(current)) {
sigset_t *sigset = &current->pending.signal;
@@ -608,43 +771,46 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
return ERR_PTR(-ERESTARTNOINTR);
}
}
- if (!oz_mode) {
- spin_lock(&sbi->fs_lock);
- ino->flags &= ~AUTOFS_INF_PENDING;
- spin_unlock(&sbi->fs_lock);
- }
}

/*
- * 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.
+ * 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 && d_unhashed(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 (!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 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 (status) {
+ dentry = ERR_PTR(status);
if (active)
dput(active);
-
return dentry;
+ } else {
+ /*
+ * Valid successful mount, return active dentry or NULL
+ * for a new dentry.
+ */
+ if (active)
+ return active;
}

- if (active)
- return active;
-
return NULL;
}

@@ -668,8 +834,6 @@ 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) {
@@ -746,7 +910,6 @@ 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);
@@ -772,7 +935,6 @@ 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);
@@ -810,8 +972,6 @@ 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)

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