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Date: Tue, 12 Aug 2014 10:48:11 -0400
From: Jeff Layton <jlayton@...marydata.com>
To: linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org
Subject: [PATCH 3/5] locks: defer freeing locks in locks_delete_lock until after i_lock has been dropped
In commit 72f98e72551fa (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.
Signed-off-by: Jeff Layton <jlayton@...marydata.com>
---
fs/locks.c | 38 ++++++++++++++++++++++++++++++--------
1 file changed, 30 insertions(+), 8 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c
index 7dd4defb4d8d..4ce087cca501 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -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));
@@ -651,12 +663,16 @@ 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);
- locks_free_lock(fl);
+ if (dispose)
+ list_add(&fl->fl_block, dispose);
+ else
+ locks_free_lock(fl);
}
/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
@@ -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 @@ out:
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);
}
/**
--
1.9.3
--
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