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Commit ed9814d8 authored by Jeff Layton's avatar Jeff Layton
Browse files

locks: defer freeing locks in locks_delete_lock until after i_lock has been dropped 



In commit 72f98e72 (locks: turn lock_flocks into a spinlock), we
moved from using the BKL to a global spinlock. With this change, we lost
the ability to block in the fl_release_private operation.

This is problematic for NFS (and probably some other filesystems as
well). Add a new list_head argument to locks_delete_lock. If that
argument is non-NULL, then queue any locks that we want to free to the
list instead of freeing them.

Then, add a new locks_dispose_list function that will walk such a list
and call locks_free_lock on them after the i_lock has been dropped.

Finally, change all of the callers of locks_delete_lock to pass in a
list_head, except for lease_modify. That function can be called long
after the i_lock has been acquired. Deferring the freeing of a lease
after unlocking it in that function is non-trivial until we overhaul
some of the spinlocking in the lease code.

Currently though, no filesystem that sets fl_release_private supports
leases, so this is not currently a problem. We'll eventually want to
make the same change in the lease code, but it needs a lot more work
before we can reasonably do so.

Acked-by: default avatarJ. Bruce Fields <bfields@fieldses.org>
Signed-off-by: default avatarJeff Layton <jlayton@primarydata.com>
parent b84d49f9

fs/locks.c

+30 −8
Original line number Diff line number Diff line
@@ -247,6 +247,18 @@ void locks_free_lock(struct file_lock *fl) 
}

EXPORT_SYMBOL(locks_free_lock);



static void

locks_dispose_list(struct list_head *dispose)

{

	struct file_lock *fl;



	while (!list_empty(dispose)) {

		fl = list_first_entry(dispose, struct file_lock, fl_block);

		list_del_init(&fl->fl_block);

		locks_free_lock(fl);

	}

}



void locks_init_lock(struct file_lock *fl)

{

	memset(fl, 0, sizeof(struct file_lock));
@@ -651,11 +663,15 @@ static void locks_unlink_lock(struct file_lock **thisfl_p) 
 *

 * Must be called with i_lock held!

 */

static void locks_delete_lock(struct file_lock **thisfl_p)

static void locks_delete_lock(struct file_lock **thisfl_p,

			      struct list_head *dispose)

{

	struct file_lock *fl = *thisfl_p;



	locks_unlink_lock(thisfl_p);

	if (dispose)

		list_add(&fl->fl_block, dispose);

	else

		locks_free_lock(fl);

}
@@ -812,6 +828,7 @@ static int flock_lock_file(struct file *filp, struct file_lock *request) 
	struct inode * inode = file_inode(filp);

	int error = 0;

	int found = 0;

	LIST_HEAD(dispose);



	if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {

		new_fl = locks_alloc_lock();
@@ -834,7 +851,7 @@ static int flock_lock_file(struct file *filp, struct file_lock *request) 
		if (request->fl_type == fl->fl_type)

			goto out;

		found = 1;

		locks_delete_lock(before);

		locks_delete_lock(before, &dispose);

		break;

	}
@@ -881,6 +898,7 @@ static int flock_lock_file(struct file *filp, struct file_lock *request) 
	spin_unlock(&inode->i_lock);

	if (new_fl)

		locks_free_lock(new_fl);

	locks_dispose_list(&dispose);

	return error;

}
@@ -894,6 +912,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str 
	struct file_lock **before;

	int error;

	bool added = false;

	LIST_HEAD(dispose);



	/*

	 * We may need two file_lock structures for this operation,
@@ -989,7 +1008,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str 
			else

				request->fl_end = fl->fl_end;

			if (added) {

				locks_delete_lock(before);

				locks_delete_lock(before, &dispose);

				continue;

			}

			request = fl;
@@ -1019,7 +1038,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str 
				 * one (This may happen several times).

				 */

				if (added) {

					locks_delete_lock(before);

					locks_delete_lock(before, &dispose);

					continue;

				}

				/*
@@ -1035,7 +1054,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str 
				locks_copy_lock(new_fl, request);

				request = new_fl;

				new_fl = NULL;

				locks_delete_lock(before);

				locks_delete_lock(before, &dispose);

				locks_insert_lock(before, request);

				added = true;

			}
@@ -1097,6 +1116,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str 
		locks_free_lock(new_fl);

	if (new_fl2)

		locks_free_lock(new_fl2);

	locks_dispose_list(&dispose);

	return error;

}
@@ -1272,7 +1292,7 @@ int lease_modify(struct file_lock **before, int arg) 
			printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);

			fl->fl_fasync = NULL;

		}

		locks_delete_lock(before);

		locks_delete_lock(before, NULL);

	}

	return 0;

}
@@ -2324,6 +2344,7 @@ void locks_remove_file(struct file *filp) 
	struct inode * inode = file_inode(filp);

	struct file_lock *fl;

	struct file_lock **before;

	LIST_HEAD(dispose);



	if (!inode->i_flock)

		return;
@@ -2369,12 +2390,13 @@ void locks_remove_file(struct file *filp) 
				fl->fl_type, fl->fl_flags,

				fl->fl_start, fl->fl_end);



			locks_delete_lock(before);

			locks_delete_lock(before, &dispose);

			continue;

 		}

		before = &fl->fl_next;

	}

	spin_unlock(&inode->i_lock);

	locks_dispose_list(&dispose);

}



/**