#include <linux/time.h>
#include <linux/rcupdate.h>
#include <linux/pid_namespace.h>
+#include <linux/hashtable.h>
#include <asm/uaccess.h>
#define for_each_lock(inode, lockp) \
for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
-static LIST_HEAD(file_lock_list);
-static LIST_HEAD(blocked_list);
+/*
+ * The global file_lock_list is only used for displaying /proc/locks. Protected
+ * by the file_lock_lock.
+ */
+static HLIST_HEAD(file_lock_list);
static DEFINE_SPINLOCK(file_lock_lock);
/*
- * Protects the two list heads above, plus the inode->i_flock list
+ * The blocked_hash is used to find POSIX lock loops for deadlock detection.
+ * It is protected by blocked_lock_lock.
+ *
+ * We hash locks by lockowner in order to optimize searching for the lock a
+ * particular lockowner is waiting on.
+ *
+ * FIXME: make this value scale via some heuristic? We generally will want more
+ * buckets when we have more lockowners holding locks, but that's a little
+ * difficult to determine without knowing what the workload will look like.
*/
-void lock_flocks(void)
-{
- spin_lock(&file_lock_lock);
-}
-EXPORT_SYMBOL_GPL(lock_flocks);
+#define BLOCKED_HASH_BITS 7
+static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS);
-void unlock_flocks(void)
-{
- spin_unlock(&file_lock_lock);
-}
-EXPORT_SYMBOL_GPL(unlock_flocks);
+/*
+ * This lock protects the blocked_hash. Generally, if you're accessing it, you
+ * want to be holding this lock.
+ *
+ * In addition, it also protects the fl->fl_block list, and the fl->fl_next
+ * pointer for file_lock structures that are acting as lock requests (in
+ * contrast to those that are acting as records of acquired locks).
+ *
+ * Note that when we acquire this lock in order to change the above fields,
+ * we often hold the i_lock as well. In certain cases, when reading the fields
+ * protected by this lock, we can skip acquiring it iff we already hold the
+ * i_lock.
+ *
+ * In particular, adding an entry to the fl_block list requires that you hold
+ * both the i_lock and the blocked_lock_lock (acquired in that order). Deleting
+ * an entry from the list however only requires the file_lock_lock.
+ */
+static DEFINE_SPINLOCK(blocked_lock_lock);
static struct kmem_cache *filelock_cache __read_mostly;
static void locks_init_lock_heads(struct file_lock *fl)
{
- INIT_LIST_HEAD(&fl->fl_link);
+ INIT_HLIST_NODE(&fl->fl_link);
INIT_LIST_HEAD(&fl->fl_block);
init_waitqueue_head(&fl->fl_wait);
}
{
BUG_ON(waitqueue_active(&fl->fl_wait));
BUG_ON(!list_empty(&fl->fl_block));
- BUG_ON(!list_empty(&fl->fl_link));
+ BUG_ON(!hlist_unhashed(&fl->fl_link));
locks_release_private(fl);
kmem_cache_free(filelock_cache, fl);
return fl1->fl_owner == fl2->fl_owner;
}
+static inline void
+locks_insert_global_locks(struct file_lock *fl)
+{
+ spin_lock(&file_lock_lock);
+ hlist_add_head(&fl->fl_link, &file_lock_list);
+ spin_unlock(&file_lock_lock);
+}
+
+static inline void
+locks_delete_global_locks(struct file_lock *fl)
+{
+ spin_lock(&file_lock_lock);
+ hlist_del_init(&fl->fl_link);
+ spin_unlock(&file_lock_lock);
+}
+
+static unsigned long
+posix_owner_key(struct file_lock *fl)
+{
+ if (fl->fl_lmops && fl->fl_lmops->lm_owner_key)
+ return fl->fl_lmops->lm_owner_key(fl);
+ return (unsigned long)fl->fl_owner;
+}
+
+static inline void
+locks_insert_global_blocked(struct file_lock *waiter)
+{
+ hash_add(blocked_hash, &waiter->fl_link, posix_owner_key(waiter));
+}
+
+static inline void
+locks_delete_global_blocked(struct file_lock *waiter)
+{
+ hash_del(&waiter->fl_link);
+}
+
/* Remove waiter from blocker's block list.
* When blocker ends up pointing to itself then the list is empty.
+ *
+ * Must be called with blocked_lock_lock held.
*/
static void __locks_delete_block(struct file_lock *waiter)
{
+ locks_delete_global_blocked(waiter);
list_del_init(&waiter->fl_block);
- list_del_init(&waiter->fl_link);
waiter->fl_next = NULL;
}
-/*
- */
static void locks_delete_block(struct file_lock *waiter)
{
- lock_flocks();
+ spin_lock(&blocked_lock_lock);
__locks_delete_block(waiter);
- unlock_flocks();
+ spin_unlock(&blocked_lock_lock);
}
/* Insert waiter into blocker's block list.
* We use a circular list so that processes can be easily woken up in
* the order they blocked. The documentation doesn't require this but
* it seems like the reasonable thing to do.
+ *
+ * Must be called with both the i_lock and blocked_lock_lock held. The fl_block
+ * list itself is protected by the file_lock_list, but by ensuring that the
+ * i_lock is also held on insertions we can avoid taking the blocked_lock_lock
+ * in some cases when we see that the fl_block list is empty.
*/
-static void locks_insert_block(struct file_lock *blocker,
- struct file_lock *waiter)
+static void __locks_insert_block(struct file_lock *blocker,
+ struct file_lock *waiter)
{
BUG_ON(!list_empty(&waiter->fl_block));
- list_add_tail(&waiter->fl_block, &blocker->fl_block);
waiter->fl_next = blocker;
+ list_add_tail(&waiter->fl_block, &blocker->fl_block);
if (IS_POSIX(blocker))
- list_add(&waiter->fl_link, &blocked_list);
+ locks_insert_global_blocked(waiter);
+}
+
+/* Must be called with i_lock held. */
+static void locks_insert_block(struct file_lock *blocker,
+ struct file_lock *waiter)
+{
+ spin_lock(&blocked_lock_lock);
+ __locks_insert_block(blocker, waiter);
+ spin_unlock(&blocked_lock_lock);
}
/*
* Wake up processes blocked waiting for blocker.
*
- * Must be called with the file_lock_lock held!
+ * Must be called with the inode->i_lock held!
*/
static void locks_wake_up_blocks(struct file_lock *blocker)
{
+ /*
+ * Avoid taking global lock if list is empty. This is safe since new
+ * blocked requests are only added to the list under the i_lock, and
+ * the i_lock is always held here. Note that removal from the fl_block
+ * list does not require the i_lock, so we must recheck list_empty()
+ * after acquiring the blocked_lock_lock.
+ */
+ if (list_empty(&blocker->fl_block))
+ return;
+
+ spin_lock(&blocked_lock_lock);
while (!list_empty(&blocker->fl_block)) {
struct file_lock *waiter;
else
wake_up(&waiter->fl_wait);
}
+ spin_unlock(&blocked_lock_lock);
}
/* Insert file lock fl into an inode's lock list at the position indicated
* by pos. At the same time add the lock to the global file lock list.
+ *
+ * Must be called with the i_lock held!
*/
static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
{
- list_add(&fl->fl_link, &file_lock_list);
-
fl->fl_nspid = get_pid(task_tgid(current));
/* insert into file's list */
fl->fl_next = *pos;
*pos = fl;
+
+ locks_insert_global_locks(fl);
}
/*
* Wake up processes that are blocked waiting for this lock,
* notify the FS that the lock has been cleared and
* finally free the lock.
+ *
+ * Must be called with the i_lock held!
*/
static void locks_delete_lock(struct file_lock **thisfl_p)
{
struct file_lock *fl = *thisfl_p;
+ locks_delete_global_locks(fl);
+
*thisfl_p = fl->fl_next;
fl->fl_next = NULL;
- list_del_init(&fl->fl_link);
if (fl->fl_nspid) {
put_pid(fl->fl_nspid);
posix_test_lock(struct file *filp, struct file_lock *fl)
{
struct file_lock *cfl;
+ struct inode *inode = file_inode(filp);
- lock_flocks();
+ spin_lock(&inode->i_lock);
for (cfl = file_inode(filp)->i_flock; cfl; cfl = cfl->fl_next) {
if (!IS_POSIX(cfl))
continue;
fl->fl_pid = pid_vnr(cfl->fl_nspid);
} else
fl->fl_type = F_UNLCK;
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
return;
}
EXPORT_SYMBOL(posix_test_lock);
{
struct file_lock *fl;
- list_for_each_entry(fl, &blocked_list, fl_link) {
+ hash_for_each_possible(blocked_hash, fl, fl_link, posix_owner_key(block_fl)) {
if (posix_same_owner(fl, block_fl))
return fl->fl_next;
}
return NULL;
}
+/* Must be called with the blocked_lock_lock held! */
static int posix_locks_deadlock(struct file_lock *caller_fl,
struct file_lock *block_fl)
{
return -ENOMEM;
}
- lock_flocks();
+ spin_lock(&inode->i_lock);
if (request->fl_flags & FL_ACCESS)
goto find_conflict;
* give it the opportunity to lock the file.
*/
if (found) {
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
cond_resched();
- lock_flocks();
+ spin_lock(&inode->i_lock);
}
find_conflict:
error = 0;
out:
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
if (new_fl)
locks_free_lock(new_fl);
return error;
new_fl2 = locks_alloc_lock();
}
- lock_flocks();
+ spin_lock(&inode->i_lock);
/*
* New lock request. Walk all POSIX locks and look for conflicts. If
* there are any, either return error or put the request on the
- * blocker's list of waiters and the global blocked_list.
+ * blocker's list of waiters and the global blocked_hash.
*/
if (request->fl_type != F_UNLCK) {
for_each_lock(inode, before) {
error = -EAGAIN;
if (!(request->fl_flags & FL_SLEEP))
goto out;
+ /*
+ * Deadlock detection and insertion into the blocked
+ * locks list must be done while holding the same lock!
+ */
error = -EDEADLK;
- if (posix_locks_deadlock(request, fl))
- goto out;
- error = FILE_LOCK_DEFERRED;
- locks_insert_block(fl, request);
+ spin_lock(&blocked_lock_lock);
+ if (likely(!posix_locks_deadlock(request, fl))) {
+ error = FILE_LOCK_DEFERRED;
+ __locks_insert_block(fl, request);
+ }
+ spin_unlock(&blocked_lock_lock);
goto out;
}
}
locks_wake_up_blocks(left);
}
out:
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
/*
* Free any unused locks.
*/
/*
* Search the lock list for this inode for any POSIX locks.
*/
- lock_flocks();
+ spin_lock(&inode->i_lock);
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (!IS_POSIX(fl))
continue;
if (fl->fl_owner != owner)
break;
}
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
return fl ? -EAGAIN : 0;
}
if (IS_ERR(new_fl))
return PTR_ERR(new_fl);
- lock_flocks();
+ spin_lock(&inode->i_lock);
time_out_leases(inode);
break_time++;
}
locks_insert_block(flock, new_fl);
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
error = wait_event_interruptible_timeout(new_fl->fl_wait,
!new_fl->fl_next, break_time);
- lock_flocks();
- __locks_delete_block(new_fl);
+ spin_lock(&inode->i_lock);
+ locks_delete_block(new_fl);
if (error >= 0) {
if (error == 0)
time_out_leases(inode);
}
out:
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
locks_free_lock(new_fl);
return error;
}
int fcntl_getlease(struct file *filp)
{
struct file_lock *fl;
+ struct inode *inode = file_inode(filp);
int type = F_UNLCK;
- lock_flocks();
+ spin_lock(&inode->i_lock);
time_out_leases(file_inode(filp));
for (fl = file_inode(filp)->i_flock; fl && IS_LEASE(fl);
fl = fl->fl_next) {
break;
}
}
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
return type;
}
* The (input) flp->fl_lmops->lm_break function is required
* by break_lease().
*
- * Called with file_lock_lock held.
+ * Called with inode->i_lock held.
*/
int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
{
int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
{
+ struct inode *inode = file_inode(filp);
int error;
- lock_flocks();
+ spin_lock(&inode->i_lock);
error = __vfs_setlease(filp, arg, lease);
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
return error;
}
static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
{
struct file_lock *fl, *ret;
+ struct inode *inode = file_inode(filp);
struct fasync_struct *new;
int error;
return -ENOMEM;
}
ret = fl;
- lock_flocks();
+ spin_lock(&inode->i_lock);
error = __vfs_setlease(filp, arg, &ret);
if (error) {
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
locks_free_lock(fl);
goto out_free_fasync;
}
new = NULL;
error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
out_free_fasync:
if (new)
fl.fl_ops->fl_release_private(&fl);
}
- lock_flocks();
+ spin_lock(&inode->i_lock);
before = &inode->i_flock;
while ((fl = *before) != NULL) {
}
before = &fl->fl_next;
}
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
}
/**
{
int status = 0;
- lock_flocks();
+ spin_lock(&blocked_lock_lock);
if (waiter->fl_next)
__locks_delete_block(waiter);
else
status = -ENOENT;
- unlock_flocks();
+ spin_unlock(&blocked_lock_lock);
return status;
}
EXPORT_SYMBOL(posix_unblock_lock);
{
struct file_lock *fl, *bfl;
- fl = list_entry(v, struct file_lock, fl_link);
+ fl = hlist_entry(v, struct file_lock, fl_link);
lock_get_status(f, fl, *((loff_t *)f->private), "");
{
loff_t *p = f->private;
- lock_flocks();
+ spin_lock(&file_lock_lock);
+ spin_lock(&blocked_lock_lock);
*p = (*pos + 1);
- return seq_list_start(&file_lock_list, *pos);
+ return seq_hlist_start(&file_lock_list, *pos);
}
static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
{
loff_t *p = f->private;
++*p;
- return seq_list_next(v, &file_lock_list, pos);
+ return seq_hlist_next(v, &file_lock_list, pos);
}
static void locks_stop(struct seq_file *f, void *v)
{
- unlock_flocks();
+ spin_unlock(&blocked_lock_lock);
+ spin_unlock(&file_lock_lock);
}
static const struct seq_operations locks_seq_operations = {
{
struct file_lock *fl;
int result = 1;
- lock_flocks();
+
+ spin_lock(&inode->i_lock);
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (IS_POSIX(fl)) {
if (fl->fl_type == F_RDLCK)
result = 0;
break;
}
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
return result;
}
{
struct file_lock *fl;
int result = 1;
- lock_flocks();
+
+ spin_lock(&inode->i_lock);
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (IS_POSIX(fl)) {
if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
result = 0;
break;
}
- unlock_flocks();
+ spin_unlock(&inode->i_lock);
return result;
}
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