user/sven/linux.git/fs/locks.c, branch v3.12.52

locks: eliminate BUG() call when there's an unexpected lock on file close

2014-12-06T15:02:10Z

commit 8c3cac5e6a85f03602ffe09c44f14418699e31ec upstream. A leftover lock on the list is surely a sign of a problem of some sort, but it's not necessarily a reason to panic the box. Instead, just log a warning with some info about the lock, and then delete it like we would any other lock. In the event that the filesystem declares a ->lock f_op, we may end up leaking something, but that's generally preferable to an immediate panic. Acked-by: J. Bruce Fields Signed-off-by: Jeff Layton Cc: Markus Blank-Burian Signed-off-by: Jiri Slaby

locks: allow __break_lease to sleep even when break_time is 0

2014-05-15T07:56:06Z

commit 4991a628a789dc5954e98e79476d9808812292ec upstream. A fl->fl_break_time of 0 has a special meaning to the lease break code that basically means "never break the lease". knfsd uses this to ensure that leases don't disappear out from under it. Unfortunately, the code in __break_lease can end up passing this value to wait_event_interruptible as a timeout, which prevents it from going to sleep at all. This causes __break_lease to spin in a tight loop and causes soft lockups. Fix this by ensuring that we pass a minimum value of 1 as a timeout instead. Cc: J. Bruce Fields Reported-by: Terry Barnaby Signed-off-by: Jeff Layton Signed-off-by: J. Bruce Fields Signed-off-by: Jiri Slaby

locks: move file_lock_list to a set of percpu hlist_heads and convert file_lock_lock to an lglock

2013-07-08T09:36:42Z

The file_lock_list is only used for /proc/locks. The vastly common case is for locks to be put onto the list and come off again, without ever being traversed. Help optimize for this use-case by moving to percpu hlist_head-s. At the same time, we can make the locking less contentious by moving to an lglock. When iterating over the lists for /proc/locks, we must take the global lock and then iterate over each CPU's list in turn. This change necessitates a new fl_link_cpu field to keep track of which CPU the entry is on. On x86_64 at least, this field is placed within an existing hole in the struct to avoid growing the size. Signed-off-by: Jeff Layton Acked-by: J. Bruce Fields Signed-off-by: Al Viro

helper for reading ->d_count

2013-07-05T14:59:33Z

Signed-off-by: Al Viro

locks: give the blocked_hash its own spinlock

2013-06-29T08:57:46Z

There's no reason we have to protect the blocked_hash and file_lock_list with the same spinlock. With the tests I have, breaking it in two gives a barely measurable performance benefit, but it seems reasonable to make this locking as granular as possible. Signed-off-by: Jeff Layton Signed-off-by: Al Viro

locks: add a new "lm_owner_key" lock operation

2013-06-29T08:57:45Z

Currently, the hashing that the locking code uses to add these values to the blocked_hash is simply calculated using fl_owner field. That's valid in most cases except for server-side lockd, which validates the owner of a lock based on fl_owner and fl_pid. In the case where you have a small number of NFS clients doing a lot of locking between different processes, you could end up with all the blocked requests sitting in a very small number of hash buckets. Add a new lm_owner_key operation to the lock_manager_operations that will generate an unsigned long to use as the key in the hashtable. That function is only implemented for server-side lockd, and simply XORs the fl_owner and fl_pid. Signed-off-by: Jeff Layton Acked-by: J. Bruce Fields Signed-off-by: Al Viro

locks: turn the blocked_list into a hashtable

2013-06-29T08:57:44Z

Break up the blocked_list into a hashtable, using the fl_owner as a key. This speeds up searching the hash chains, which is especially significant for deadlock detection. Note that the initial implementation assumes that hashing on fl_owner is sufficient. In most cases it should be, with the notable exception being server-side lockd, which compares ownership using a tuple of the nlm_host and the pid sent in the lock request. So, this may degrade to a single hash bucket when you only have a single NFS client. That will be addressed in a later patch. The careful observer may note that this patch leaves the file_lock_list alone. There's much less of a case for turning the file_lock_list into a hashtable. The only user of that list is the code that generates /proc/locks, and it always walks the entire list. Signed-off-by: Jeff Layton Acked-by: J. Bruce Fields Signed-off-by: Al Viro

locks: convert fl_link to a hlist_node

2013-06-29T08:57:44Z

Testing has shown that iterating over the blocked_list for deadlock detection turns out to be a bottleneck. In order to alleviate that, begin the process of turning it into a hashtable. We start by turning the fl_link into a hlist_node and the global lists into hlists. A later patch will do the conversion of the blocked_list to a hashtable. Signed-off-by: Jeff Layton Acked-by: J. Bruce Fields Signed-off-by: Al Viro

locks: avoid taking global lock if possible when waking up blocked waiters

2013-06-29T08:57:43Z

Since we always hold the i_lock when inserting a new waiter onto the fl_block list, we can avoid taking the global lock at all if we find that it's empty when we go to wake up blocked waiters. Signed-off-by: Jeff Layton Signed-off-by: Al Viro

locks: protect most of the file_lock handling with i_lock

2013-06-29T08:57:42Z

Having a global lock that protects all of this code is a clear scalability problem. Instead of doing that, move most of the code to be protected by the i_lock instead. The exceptions are the global lists that the ->fl_link sits on, and the ->fl_block list. ->fl_link is what connects these structures to the global lists, so we must ensure that we hold those locks when iterating over or updating these lists. Furthermore, sound deadlock detection requires that we hold the blocked_list state steady while checking for loops. We also must ensure that the search and update to the list are atomic. For the checking and insertion side of the blocked_list, push the acquisition of the global lock into __posix_lock_file and ensure that checking and update of the blocked_list is done without dropping the lock in between. On the removal side, when waking up blocked lock waiters, take the global lock before walking the blocked list and dequeue the waiters from the global list prior to removal from the fl_block list. With this, deadlock detection should be race free while we minimize excessive file_lock_lock thrashing. Finally, in order to avoid a lock inversion problem when handling /proc/locks output we must ensure that manipulations of the fl_block list are also protected by the file_lock_lock. Signed-off-by: Jeff Layton Signed-off-by: Al Viro