locks: move freeing of leases outside of i_lock

There was only one place where we still could free a file_lock while
holding the i_lock -- lease_modify. Add a new list_head argument to the
lm_change operation, pass in a private list when calling it, and fix
those callers to dispose of the list once the lock has been dropped.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

4 files changed, 30 insertions, 20 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 4af288e38f13..94d93b1f8b53 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -469,8 +469,7 @@ prototypes:
 };
 
 locking rules:
-        All may block except for ->setlease.
-        No VFS locks held on entry except for ->setlease.
+        All may block.
 
 ->llseek() locking has moved from llseek to the individual llseek
 implementations.  If your fs is not using generic_file_llseek, you
diff --git a/fs/locks.c b/fs/locks.c
index eb463257f867..c0f789dfa655 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1292,7 +1292,7 @@ static void lease_clear_pending(struct file_lock *fl, int arg)
 }
 
 /* We already had a lease on this file; just change its type */
-int lease_modify(struct file_lock **before, int arg)
+int lease_modify(struct file_lock **before, int arg, struct list_head *dispose)
 {
         struct file_lock *fl = *before;
         int error = assign_type(fl, arg);
@@ -1311,7 +1311,7 @@ int lease_modify(struct file_lock **before, int arg)
                         printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
                         fl->fl_fasync = NULL;
                 }
-                locks_delete_lock(before, NULL);
+                locks_delete_lock(before, dispose);
         }
         return 0;
 }
@@ -1325,7 +1325,7 @@ static bool past_time(unsigned long then)
         return time_after(jiffies, then);
 }
 
-static void time_out_leases(struct inode *inode)
+static void time_out_leases(struct inode *inode, struct list_head *dispose)
 {
         struct file_lock **before;
         struct file_lock *fl;
@@ -1336,9 +1336,9 @@ static void time_out_leases(struct inode *inode)
         while ((fl = *before) && IS_LEASE(fl) && lease_breaking(fl)) {
                 trace_time_out_leases(inode, fl);
                 if (past_time(fl->fl_downgrade_time))
-                        lease_modify(before, F_RDLCK);
+                        lease_modify(before, F_RDLCK, dispose);
                 if (past_time(fl->fl_break_time))
-                        lease_modify(before, F_UNLCK);
+                        lease_modify(before, F_UNLCK, dispose);
                 if (fl == *before)      /* lease_modify may have freed fl */
                         before = &fl->fl_next;
         }
@@ -1373,6 +1373,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
         int i_have_this_lease = 0;
         bool lease_conflict = false;
         int want_write = (mode & O_ACCMODE) != O_RDONLY;
+        LIST_HEAD(dispose);
 
         new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
         if (IS_ERR(new_fl))
@@ -1381,7 +1382,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
 
         spin_lock(&inode->i_lock);
 
-        time_out_leases(inode);
+        time_out_leases(inode, &dispose);
 
         flock = inode->i_flock;
         if ((flock == NULL) || !IS_LEASE(flock))
@@ -1436,6 +1437,7 @@ restart:
         locks_insert_block(flock, new_fl);
         trace_break_lease_block(inode, new_fl);
         spin_unlock(&inode->i_lock);
+        locks_dispose_list(&dispose);
         error = wait_event_interruptible_timeout(new_fl->fl_wait,
                                                 !new_fl->fl_next, break_time);
         spin_lock(&inode->i_lock);
@@ -1443,7 +1445,7 @@ restart:
         locks_delete_block(new_fl);
         if (error >= 0) {
                 if (error == 0)
-                        time_out_leases(inode);
+                        time_out_leases(inode, &dispose);
                 /*
                  * Wait for the next conflicting lease that has not been
                  * broken yet
@@ -1458,6 +1460,7 @@ restart:
 
 out:
         spin_unlock(&inode->i_lock);
+        locks_dispose_list(&dispose);
         locks_free_lock(new_fl);
         return error;
 }
@@ -1522,9 +1525,10 @@ int fcntl_getlease(struct file *filp)
         struct file_lock *fl;
         struct inode *inode = file_inode(filp);
         int type = F_UNLCK;
+        LIST_HEAD(dispose);
 
         spin_lock(&inode->i_lock);
-        time_out_leases(file_inode(filp));
+        time_out_leases(file_inode(filp), &dispose);
         for (fl = file_inode(filp)->i_flock; fl && IS_LEASE(fl);
                         fl = fl->fl_next) {
                 if (fl->fl_file == filp) {
@@ -1533,6 +1537,7 @@ int fcntl_getlease(struct file *filp)
                 }
         }
         spin_unlock(&inode->i_lock);
+        locks_dispose_list(&dispose);
         return type;
 }
 
@@ -1570,6 +1575,7 @@ generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **pr
         struct inode *inode = dentry->d_inode;
         bool is_deleg = (*flp)->fl_flags & FL_DELEG;
         int error;
+        LIST_HEAD(dispose);
 
         lease = *flp;
         trace_generic_add_lease(inode, lease);
@@ -1593,7 +1599,7 @@ generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **pr
         }
 
         spin_lock(&inode->i_lock);
-        time_out_leases(inode);
+        time_out_leases(inode, &dispose);
         error = check_conflicting_open(dentry, arg);
         if (error)
                 goto out;
@@ -1630,7 +1636,7 @@ generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **pr
 
         if (my_before != NULL) {
                 lease = *my_before;
-                error = lease->fl_lmops->lm_change(my_before, arg);
+                error = lease->fl_lmops->lm_change(my_before, arg, &dispose);
                 if (error)
                         goto out;
                 goto out_setup;
@@ -1660,6 +1666,7 @@ out_setup:
                 lease->fl_lmops->lm_setup(lease, priv);
 out:
         spin_unlock(&inode->i_lock);
+        locks_dispose_list(&dispose);
         if (is_deleg)
                 mutex_unlock(&inode->i_mutex);
         if (!error && !my_before)
@@ -1676,8 +1683,10 @@ static int generic_delete_lease(struct file *filp)
         struct file_lock *fl, **before;
         struct dentry *dentry = filp->f_path.dentry;
         struct inode *inode = dentry->d_inode;
+        LIST_HEAD(dispose);
 
         spin_lock(&inode->i_lock);
+        time_out_leases(inode, &dispose);
         for (before = &inode->i_flock;
                         ((fl = *before) != NULL) && IS_LEASE(fl);
                         before = &fl->fl_next) {
@@ -1686,8 +1695,9 @@ static int generic_delete_lease(struct file *filp)
         }
         trace_generic_delete_lease(inode, fl);
         if (fl)
-                error = fl->fl_lmops->lm_change(before, F_UNLCK);
+                error = fl->fl_lmops->lm_change(before, F_UNLCK, &dispose);
         spin_unlock(&inode->i_lock);
+        locks_dispose_list(&dispose);
         return error;
 }
 
@@ -2372,7 +2382,7 @@ void locks_remove_file(struct file *filp)
         while ((fl = *before) != NULL) {
                 if (fl->fl_file == filp) {
                         if (IS_LEASE(fl)) {
-                                lease_modify(before, F_UNLCK);
+                                lease_modify(before, F_UNLCK, &dispose);
                                 continue;
                         }
 
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 5349528136e2..604ab6decd28 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3427,11 +3427,11 @@ static void nfsd_break_deleg_cb(struct file_lock *fl)
         spin_unlock(&fp->fi_lock);
 }
 
-static
-int nfsd_change_deleg_cb(struct file_lock **onlist, int arg)
+static int
+nfsd_change_deleg_cb(struct file_lock **onlist, int arg, struct list_head *dispose)
 {
         if (arg & F_UNLCK)
-                return lease_modify(onlist, arg);
+                return lease_modify(onlist, arg, dispose);
         else
                 return -EAGAIN;
 }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9a6d56154dd5..f419f718e447 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -873,7 +873,7 @@ struct lock_manager_operations {
         void (*lm_notify)(struct file_lock *);  /* unblock callback */
         int (*lm_grant)(struct file_lock *, int);
         void (*lm_break)(struct file_lock *);
-        int (*lm_change)(struct file_lock **, int);
+        int (*lm_change)(struct file_lock **, int, struct list_head *);
         void (*lm_setup)(struct file_lock *, void **);
 };
 
@@ -985,7 +985,7 @@ extern int __break_lease(struct inode *inode, unsigned int flags, unsigned int t
 extern void lease_get_mtime(struct inode *, struct timespec *time);
 extern int generic_setlease(struct file *, long, struct file_lock **, void **priv);
 extern int vfs_setlease(struct file *, long, struct file_lock **, void **);
-extern int lease_modify(struct file_lock **, int);
+extern int lease_modify(struct file_lock **, int, struct list_head *);
 #else /* !CONFIG_FILE_LOCKING */
 static inline int fcntl_getlk(struct file *file, unsigned int cmd,
                               struct flock __user *user)
@@ -1112,7 +1112,8 @@ static inline int vfs_setlease(struct file *filp, long arg,
         return -EINVAL;
 }
 
-static inline int lease_modify(struct file_lock **before, int arg)
+static inline int lease_modify(struct file_lock **before, int arg,
+                               struct list_head *dispose)
 {
         return -EINVAL;
 }