[PATCH fs/locks 2 of 3] Use proper tgid in locks_remove_posix

[Olaf Kirch <okir@suse.de>]

# Subject: [NFS] Use proper tgid in locks_remove_posix
# 
# This patch fixes a problem with lost unlock calls in multithreaded
# applications. locks_remove_posix would send a single unlock call with
# the task group ID of the current process, which may not be the same as
# the tgid of the lock. This patch ensures that we send separate unlock
# calls for different fl_pid values.
# 
# Signed-off-by: Olaf Kirch <okir@suse.de>

Index: linux-2.6.12/fs/locks.c
===================================================================
--- linux-2.6.12.orig/fs/locks.c	2005-07-11 12:16:41.000000000 +0200
+++ linux-2.6.12/fs/locks.c	2005-07-11 12:17:15.000000000 +0200
@@ -1811,47 +1811,60 @@ out:
 void locks_remove_posix(struct file *filp, fl_owner_t owner)
 {
 	struct file_lock lock, **before;
+	pid_t tgid;
+	int more;
 
-	/*
-	 * If there are no locks held on this file, we don't need to call
-	 * posix_lock_file().  Another process could be setting a lock on this
-	 * file at the same time, but we wouldn't remove that lock anyway.
-	 */
-	before = &filp->f_dentry->d_inode->i_flock;
-	if (*before == NULL)
-		return;
-
-	lock.fl_type = F_UNLCK;
-	lock.fl_flags = FL_POSIX;
-	lock.fl_start = 0;
-	lock.fl_end = OFFSET_MAX;
-	lock.fl_owner = owner;
-	lock.fl_pid = current->tgid;
-	lock.fl_file = filp;
-	lock.fl_ops = NULL;
-	lock.fl_lmops = NULL;
-
-	if (filp->f_op && filp->f_op->lock != NULL) {
-		filp->f_op->lock(filp, F_SETLK, &lock);
-		goto out;
-	}
+	do {
+		/*
+		 * If there are no locks held on this file, we don't need to call
+		 * posix_lock_file().  Another process could be setting a lock on this
+		 * file at the same time, but we wouldn't remove that lock anyway.
+		 */
+		before = &filp->f_dentry->d_inode->i_flock;
+		if (*before == NULL)
+			return;
+
+		more = 0;
+		tgid = 0;
+
+		/* Can't use posix_lock_file here; we need to remove it no matter
+		 * which pid we have.
+		 */
+		lock_kernel();
+		while (*before != NULL) {
+			struct file_lock *fl = *before;
+			if (IS_POSIX(fl) && posix_same_owner(fl, &lock)) {
+				if (tgid == 0 || tgid == fl->fl_pid) {
+					tgid = fl->fl_pid;
+					locks_delete_lock(before);
+					continue;
+				}
+				/* We have locks owned by a different tgid.
+				 * Need to come back. */
+				more = 1;
+			}
+			before = &fl->fl_next;
+		}
+		unlock_kernel();
 
-	/* Can't use posix_lock_file here; we need to remove it no matter
-	 * which pid we have.
-	 */
-	lock_kernel();
-	while (*before != NULL) {
-		struct file_lock *fl = *before;
-		if (IS_POSIX(fl) && posix_same_owner(fl, &lock)) {
-			locks_delete_lock(before);
-			continue;
+		if (tgid != 0) {
+			lock.fl_type = F_UNLCK;
+			lock.fl_flags = FL_POSIX;
+			lock.fl_start = 0;
+			lock.fl_end = OFFSET_MAX;
+			lock.fl_owner = owner;
+			lock.fl_pid = tgid;
+			lock.fl_file = filp;
+			lock.fl_ops = NULL;
+			lock.fl_lmops = NULL;
+
+			if (filp->f_op && filp->f_op->lock != NULL) {
+				filp->f_op->lock(filp, F_SETLK, &lock);
+				if (lock.fl_ops && lock.fl_ops->fl_release_private)
+					lock.fl_ops->fl_release_private(&lock);
+			}
 		}
-		before = &fl->fl_next;
-	}
-	unlock_kernel();
-out:
-	if (lock.fl_ops && lock.fl_ops->fl_release_private)
-		lock.fl_ops->fl_release_private(&lock);
+	} while (more);
 }
 
 EXPORT_SYMBOL(locks_remove_posix);

-- 
Olaf Kirch   |  --- o --- Nous sommes du soleil we love when we play
okir@suse.de |    / | \   sol.dhoop.naytheet.ah kin.ir.samse.qurax


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