1 files changed, 21 insertions, 2 deletions

diff --git a/fs/locks.c b/fs/locks.c
index 1ad29c9b6252..b0b41a64e10b 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -725,6 +725,10 @@ next_task:
 /* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
  * at the head of the list, but that's secret knowledge known only to
  * flock_lock_file and posix_lock_file.
+ *
+ * Note that if called with an FL_EXISTS argument, the caller may determine
+ * whether or not a lock was successfully freed by testing the return
+ * value for -ENOENT.
  */
 static int flock_lock_file(struct file *filp, struct file_lock *request)
 {
@@ -735,6 +739,8 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
         int found = 0;
 
         lock_kernel();
+        if (request->fl_flags & FL_ACCESS)
+                goto find_conflict;
         for_each_lock(inode, before) {
                 struct file_lock *fl = *before;
                 if (IS_POSIX(fl))
@@ -750,8 +756,11 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
                 break;
         }
 
-        if (request->fl_type == F_UNLCK)
+        if (request->fl_type == F_UNLCK) {
+                if ((request->fl_flags & FL_EXISTS) && !found)
+                        error = -ENOENT;
                 goto out;
+        }
 
         error = -ENOMEM;
         new_fl = locks_alloc_lock();
@@ -764,6 +773,7 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
         if (found)
                 cond_resched();
 
+find_conflict:
         for_each_lock(inode, before) {
                 struct file_lock *fl = *before;
                 if (IS_POSIX(fl))
@@ -777,6 +787,8 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
                         locks_insert_block(fl, request);
                 goto out;
         }
+        if (request->fl_flags & FL_ACCESS)
+                goto out;
         locks_copy_lock(new_fl, request);
         locks_insert_lock(&inode->i_flock, new_fl);
         new_fl = NULL;
@@ -948,8 +960,11 @@ static int __posix_lock_file_conf(struct inode *inode, struct file_lock *request
 
         error = 0;
         if (!added) {
-                if (request->fl_type == F_UNLCK)
+                if (request->fl_type == F_UNLCK) {
+                        if (request->fl_flags & FL_EXISTS)
+                                error = -ENOENT;
                         goto out;
+                }
 
                 if (!new_fl) {
                         error = -ENOLCK;
@@ -996,6 +1011,10 @@ static int __posix_lock_file_conf(struct inode *inode, struct file_lock *request
  * Add a POSIX style lock to a file.
  * We merge adjacent & overlapping locks whenever possible.
  * POSIX locks are sorted by owner task, then by starting address
+ *
+ * Note that if called with an FL_EXISTS argument, the caller may determine
+ * whether or not a lock was successfully freed by testing the return
+ * value for -ENOENT.
  */
 int posix_lock_file(struct file *filp, struct file_lock *fl)
 {