[PATCH 1/4] locks: prevent ENOMEM on lease unlock

J. Bruce Fields
2010-10-30T21:31:31Z

Removing a lock shouldn't require any allocations; a failure due to
ENOMEM leaves the caller with a choice between retrying or giving up and
leaking an unused lease.

Next we should split the other lease calls into add and delete cases.
I wanted to start with just the bugfix.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
fs/locks.c | 43 ++++++++++++++++++++++++++++++-------------
1 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index 50ec159..06c7773 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1441,7 +1441,8 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
return 0;

out:
- locks_free_lock(lease);
+ if (arg != F_UNLCK)
+ locks_free_lock(lease);
return error;
}
EXPORT_SYMBOL(generic_setlease);
@@ -1493,17 +1494,16 @@ int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
}
EXPORT_SYMBOL_GPL(vfs_setlease);

-/**
- * fcntl_setlease - sets a lease on an open file
- * @fd: open file descriptor
- * @filp: file pointer
- * @arg: type of lease to obtain
- *
- * Call this fcntl to establish a lease on the file.
- * Note that you also need to call %F_SETSIG to
- * receive a signal when the lease is broken.
- */
-int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
+static int do_fcntl_delete_lease(struct file *filp)
+{
+ struct file_lock fl, *flp = &fl;
+
+ lease_init(filp, F_UNLCK, flp);
+
+ return vfs_setlease(filp, F_UNLCK, &flp);
+}
+
+static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
{
struct file_lock *fl;
struct fasync_struct *new;
@@ -1521,7 +1521,7 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
}
lock_flocks();
error = __vfs_setlease(filp, arg, &fl);
- if (error || arg == F_UNLCK)
+ if (error)
goto out_unlock;

/*
@@ -1550,6 +1550,23 @@ out_unlock:
}

/**
+ * fcntl_setlease - sets a lease on an open file
+ * @fd: open file descriptor
+ * @filp: file pointer
+ * @arg: type of lease to obtain
+ *
+ * Call this fcntl to establish a lease on the file.
+ * Note that you also need to call %F_SETSIG to
+ * receive a signal when the lease is broken.
+ */
+int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
+{
+ if (arg == F_UNLCK)
+ return do_fcntl_delete_lease(filp);
+ return do_fcntl_add_lease(fd, filp, arg);
+}
+
+/**
* flock_lock_file_wait - Apply a FLOCK-style lock to a file
* @filp: The file to apply the lock to
* @fl: The lock to be applied
--
1.7.1