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

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In commit 72f98e7255 (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: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
This commit is contained in:
Jeff Layton 2014-08-11 14:20:31 -04:00
parent b84d49f944
commit ed9814d858
1 changed files with 30 additions and 8 deletions
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38
fs/locks.c
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@ -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);
}
/**