locks: implement delegations

Implement NFSv4 delegations at the vfs level using the new FL_DELEG lock
type.

Note nfsd is the only delegation user and is only using read
delegations.  Warn on any attempt to set a write delegation for now.
We'll come back to that case later.

Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/locks.c b/fs/locks.c
index 079abcd8a8361cb71a10f3cc413f4d6b6032b760..f99d52bdd05ab8570b7f2c016b0fa6f99a2dc4db 100644 (file)
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1292,28 +1292,40 @@ static void time_out_leases(struct inode *inode)
        }
 }
 
+static bool leases_conflict(struct file_lock *lease, struct file_lock *breaker)
+{
+       if ((breaker->fl_flags & FL_DELEG) && (lease->fl_flags & FL_LEASE))
+               return false;
+       return locks_conflict(breaker, lease);
+}
+
 /**
  *     __break_lease   -       revoke all outstanding leases on file
  *     @inode: the inode of the file to return
- *     @mode: the open mode (read or write)
+ *     @mode: O_RDONLY: break only write leases; O_WRONLY or O_RDWR:
+ *         break all leases
+ *     @type: FL_LEASE: break leases and delegations; FL_DELEG: break
+ *         only delegations
  *
  *     break_lease (inlined for speed) has checked there already is at least
  *     some kind of lock (maybe a lease) on this file.  Leases are broken on
  *     a call to open() or truncate().  This function can sleep unless you
  *     specified %O_NONBLOCK to your open().
  */
-int __break_lease(struct inode *inode, unsigned int mode)
+int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
 {
        int error = 0;
        struct file_lock *new_fl, *flock;
        struct file_lock *fl;
        unsigned long break_time;
        int i_have_this_lease = 0;
+       bool lease_conflict = false;
        int want_write = (mode & O_ACCMODE) != O_RDONLY;
 
        new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
        if (IS_ERR(new_fl))
                return PTR_ERR(new_fl);
+       new_fl->fl_flags = type;
 
        spin_lock(&inode->i_lock);
 
@@ -1323,13 +1335,16 @@ int __break_lease(struct inode *inode, unsigned int mode)
        if ((flock == NULL) || !IS_LEASE(flock))
                goto out;
 
-       if (!locks_conflict(flock, new_fl))
+       for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
+               if (leases_conflict(fl, new_fl)) {
+                       lease_conflict = true;
+                       if (fl->fl_owner == current->files)
+                               i_have_this_lease = 1;
+               }
+       }
+       if (!lease_conflict)
                goto out;
 
-       for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
-               if (fl->fl_owner == current->files)
-                       i_have_this_lease = 1;
-
        break_time = 0;
        if (lease_break_time > 0) {
                break_time = jiffies + lease_break_time * HZ;
@@ -1338,6 +1353,8 @@ int __break_lease(struct inode *inode, unsigned int mode)
        }
 
        for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
+               if (!leases_conflict(fl, new_fl))
+                       continue;
                if (want_write) {
                        if (fl->fl_flags & FL_UNLOCK_PENDING)
                                continue;
@@ -1379,7 +1396,7 @@ restart:
                 */
                for (flock = inode->i_flock; flock && IS_LEASE(flock);
                                flock = flock->fl_next) {
-                       if (locks_conflict(new_fl, flock))
+                       if (leases_conflict(new_fl, flock))
                                goto restart;
                }
                error = 0;
@@ -1460,9 +1477,26 @@ static int generic_add_lease(struct file *filp, long arg, struct file_lock **flp
        struct file_lock *fl, **before, **my_before = NULL, *lease;
        struct dentry *dentry = filp->f_path.dentry;
        struct inode *inode = dentry->d_inode;
+       bool is_deleg = (*flp)->fl_flags & FL_DELEG;
        int error;
 
        lease = *flp;
+       /*
+        * In the delegation case we need mutual exclusion with
+        * a number of operations that take the i_mutex.  We trylock
+        * because delegations are an optional optimization, and if
+        * there's some chance of a conflict--we'd rather not
+        * bother, maybe that's a sign this just isn't a good file to
+        * hand out a delegation on.
+        */
+       if (is_deleg && !mutex_trylock(&inode->i_mutex))
+               return -EAGAIN;
+
+       if (is_deleg && arg == F_WRLCK) {
+               /* Write delegations are not currently supported: */
+               WARN_ON_ONCE(1);
+               return -EINVAL;
+       }
 
        error = -EAGAIN;
        if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
@@ -1514,9 +1548,10 @@ static int generic_add_lease(struct file *filp, long arg, struct file_lock **flp
                goto out;
 
        locks_insert_lock(before, lease);
-       return 0;
-
+       error = 0;
 out:
+       if (is_deleg)
+               mutex_unlock(&inode->i_mutex);
        return error;
 }
 

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 129e150f9e9485f76b3889e1d18a21b027d050a8..8e4be1be1a6257238f99c4ebde0ff8ce26c29c87 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1022,7 +1022,7 @@ extern int vfs_test_lock(struct file *, struct file_lock *);
 extern int vfs_lock_file(struct file *, unsigned int, struct file_lock *, struct file_lock *);
 extern int vfs_cancel_lock(struct file *filp, struct file_lock *fl);
 extern int flock_lock_file_wait(struct file *filp, struct file_lock *fl);
-extern int __break_lease(struct inode *inode, unsigned int flags);
+extern int __break_lease(struct inode *inode, unsigned int flags, unsigned int type);
 extern void lease_get_mtime(struct inode *, struct timespec *time);
 extern int generic_setlease(struct file *, long, struct file_lock **);
 extern int vfs_setlease(struct file *, long, struct file_lock **);
@@ -1131,7 +1131,7 @@ static inline int flock_lock_file_wait(struct file *filp,
        return -ENOLCK;
 }
 
-static inline int __break_lease(struct inode *inode, unsigned int mode)
+static inline int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
 {
        return 0;
 }
@@ -1961,9 +1961,17 @@ static inline int locks_verify_truncate(struct inode *inode,
 static inline int break_lease(struct inode *inode, unsigned int mode)
 {
        if (inode->i_flock)
-               return __break_lease(inode, mode);
+               return __break_lease(inode, mode, FL_LEASE);
        return 0;
 }
+
+static inline int break_deleg(struct inode *inode, unsigned int mode)
+{
+       if (inode->i_flock)
+               return __break_lease(inode, mode, FL_DELEG);
+       return 0;
+}
+
 #else /* !CONFIG_FILE_LOCKING */
 static inline int locks_mandatory_locked(struct inode *inode)
 {
@@ -2003,6 +2011,10 @@ static inline int break_lease(struct inode *inode, unsigned int mode)
        return 0;
 }
 
+static inline int break_deleg(struct inode *inode, unsigned int mode)
+{
+       return 0;
+}
 #endif /* CONFIG_FILE_LOCKING */
 
 /* fs/open.c */