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-rw-r--r--fs/locks.c18
-rw-r--r--include/linux/fs.h1
2 files changed, 17 insertions, 2 deletions
diff --git a/fs/locks.c b/fs/locks.c
index 1ad29c9..50cb0a2 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)
{
@@ -750,8 +754,11 @@ 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();
@@ -948,8 +955,11 @@ 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 +1006,10 @@ 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)
{
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 134b320..43aef9b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -716,6 +716,7 @@ extern spinlock_t files_lock;
#define FL_POSIX 1
#define FL_FLOCK 2
#define FL_ACCESS 8 /* not trying to lock, just looking */
+#define FL_EXISTS 16 /* when unlocking, test for existence */
#define FL_LEASE 32 /* lease held on this file */
#define FL_CLOSE 64 /* unlock on close */
#define FL_SLEEP 128 /* A blocking lock */
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