Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 2212 insertions, 0 deletions

diff --git a/fs/locks.c b/fs/locks.c
new file mode 100644
index 000000000000..1792ce547af7
--- /dev/null
+++ b/fs/locks.c
@@ -0,0 +1,2212 @@
+/*
+ *  linux/fs/locks.c
+ *
+ *  Provide support for fcntl()'s F_GETLK, F_SETLK, and F_SETLKW calls.
+ *  Doug Evans (dje@spiff.uucp), August 07, 1992
+ *
+ *  Deadlock detection added.
+ *  FIXME: one thing isn't handled yet:
+ *	- mandatory locks (requires lots of changes elsewhere)
+ *  Kelly Carmichael (kelly@[142.24.8.65]), September 17, 1994.
+ *
+ *  Miscellaneous edits, and a total rewrite of posix_lock_file() code.
+ *  Kai Petzke (wpp@marie.physik.tu-berlin.de), 1994
+ *  
+ *  Converted file_lock_table to a linked list from an array, which eliminates
+ *  the limits on how many active file locks are open.
+ *  Chad Page (pageone@netcom.com), November 27, 1994
+ * 
+ *  Removed dependency on file descriptors. dup()'ed file descriptors now
+ *  get the same locks as the original file descriptors, and a close() on
+ *  any file descriptor removes ALL the locks on the file for the current
+ *  process. Since locks still depend on the process id, locks are inherited
+ *  after an exec() but not after a fork(). This agrees with POSIX, and both
+ *  BSD and SVR4 practice.
+ *  Andy Walker (andy@lysaker.kvaerner.no), February 14, 1995
+ *
+ *  Scrapped free list which is redundant now that we allocate locks
+ *  dynamically with kmalloc()/kfree().
+ *  Andy Walker (andy@lysaker.kvaerner.no), February 21, 1995
+ *
+ *  Implemented two lock personalities - FL_FLOCK and FL_POSIX.
+ *
+ *  FL_POSIX locks are created with calls to fcntl() and lockf() through the
+ *  fcntl() system call. They have the semantics described above.
+ *
+ *  FL_FLOCK locks are created with calls to flock(), through the flock()
+ *  system call, which is new. Old C libraries implement flock() via fcntl()
+ *  and will continue to use the old, broken implementation.
+ *
+ *  FL_FLOCK locks follow the 4.4 BSD flock() semantics. They are associated
+ *  with a file pointer (filp). As a result they can be shared by a parent
+ *  process and its children after a fork(). They are removed when the last
+ *  file descriptor referring to the file pointer is closed (unless explicitly
+ *  unlocked). 
+ *
+ *  FL_FLOCK locks never deadlock, an existing lock is always removed before
+ *  upgrading from shared to exclusive (or vice versa). When this happens
+ *  any processes blocked by the current lock are woken up and allowed to
+ *  run before the new lock is applied.
+ *  Andy Walker (andy@lysaker.kvaerner.no), June 09, 1995
+ *
+ *  Removed some race conditions in flock_lock_file(), marked other possible
+ *  races. Just grep for FIXME to see them. 
+ *  Dmitry Gorodchanin (pgmdsg@ibi.com), February 09, 1996.
+ *
+ *  Addressed Dmitry's concerns. Deadlock checking no longer recursive.
+ *  Lock allocation changed to GFP_ATOMIC as we can't afford to sleep
+ *  once we've checked for blocking and deadlocking.
+ *  Andy Walker (andy@lysaker.kvaerner.no), April 03, 1996.
+ *
+ *  Initial implementation of mandatory locks. SunOS turned out to be
+ *  a rotten model, so I implemented the "obvious" semantics.
+ *  See 'Documentation/mandatory.txt' for details.
+ *  Andy Walker (andy@lysaker.kvaerner.no), April 06, 1996.
+ *
+ *  Don't allow mandatory locks on mmap()'ed files. Added simple functions to
+ *  check if a file has mandatory locks, used by mmap(), open() and creat() to
+ *  see if system call should be rejected. Ref. HP-UX/SunOS/Solaris Reference
+ *  Manual, Section 2.
+ *  Andy Walker (andy@lysaker.kvaerner.no), April 09, 1996.
+ *
+ *  Tidied up block list handling. Added '/proc/locks' interface.
+ *  Andy Walker (andy@lysaker.kvaerner.no), April 24, 1996.
+ *
+ *  Fixed deadlock condition for pathological code that mixes calls to
+ *  flock() and fcntl().
+ *  Andy Walker (andy@lysaker.kvaerner.no), April 29, 1996.
+ *
+ *  Allow only one type of locking scheme (FL_POSIX or FL_FLOCK) to be in use
+ *  for a given file at a time. Changed the CONFIG_LOCK_MANDATORY scheme to
+ *  guarantee sensible behaviour in the case where file system modules might
+ *  be compiled with different options than the kernel itself.
+ *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
+ *
+ *  Added a couple of missing wake_up() calls. Thanks to Thomas Meckel
+ *  (Thomas.Meckel@mni.fh-giessen.de) for spotting this.
+ *  Andy Walker (andy@lysaker.kvaerner.no), May 15, 1996.
+ *
+ *  Changed FL_POSIX locks to use the block list in the same way as FL_FLOCK
+ *  locks. Changed process synchronisation to avoid dereferencing locks that
+ *  have already been freed.
+ *  Andy Walker (andy@lysaker.kvaerner.no), Sep 21, 1996.
+ *
+ *  Made the block list a circular list to minimise searching in the list.
+ *  Andy Walker (andy@lysaker.kvaerner.no), Sep 25, 1996.
+ *
+ *  Made mandatory locking a mount option. Default is not to allow mandatory
+ *  locking.
+ *  Andy Walker (andy@lysaker.kvaerner.no), Oct 04, 1996.
+ *
+ *  Some adaptations for NFS support.
+ *  Olaf Kirch (okir@monad.swb.de), Dec 1996,
+ *
+ *  Fixed /proc/locks interface so that we can't overrun the buffer we are handed.
+ *  Andy Walker (andy@lysaker.kvaerner.no), May 12, 1997.
+ *
+ *  Use slab allocator instead of kmalloc/kfree.
+ *  Use generic list implementation from <linux/list.h>.
+ *  Sped up posix_locks_deadlock by only considering blocked locks.
+ *  Matthew Wilcox <willy@debian.org>, March, 2000.
+ *
+ *  Leases and LOCK_MAND
+ *  Matthew Wilcox <willy@debian.org>, June, 2000.
+ *  Stephen Rothwell <sfr@canb.auug.org.au>, June, 2000.
+ */
+
+#include <linux/capability.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/security.h>
+#include <linux/slab.h>
+#include <linux/smp_lock.h>
+#include <linux/syscalls.h>
+#include <linux/time.h>
+
+#include <asm/semaphore.h>
+#include <asm/uaccess.h>
+
+#define IS_POSIX(fl)	(fl->fl_flags & FL_POSIX)
+#define IS_FLOCK(fl)	(fl->fl_flags & FL_FLOCK)
+#define IS_LEASE(fl)	(fl->fl_flags & FL_LEASE)
+
+int leases_enable = 1;
+int lease_break_time = 45;
+
+#define for_each_lock(inode, lockp) \
+	for (lockp = &inode->i_flock; *lockp != NULL; lockp = &(*lockp)->fl_next)
+
+LIST_HEAD(file_lock_list);
+
+EXPORT_SYMBOL(file_lock_list);
+
+static LIST_HEAD(blocked_list);
+
+static kmem_cache_t *filelock_cache;
+
+/* Allocate an empty lock structure. */
+static struct file_lock *locks_alloc_lock(void)
+{
+	return kmem_cache_alloc(filelock_cache, SLAB_KERNEL);
+}
+
+/* Free a lock which is not in use. */
+static inline void locks_free_lock(struct file_lock *fl)
+{
+	if (fl == NULL) {
+		BUG();
+		return;
+	}
+	if (waitqueue_active(&fl->fl_wait))
+		panic("Attempting to free lock with active wait queue");
+
+	if (!list_empty(&fl->fl_block))
+		panic("Attempting to free lock with active block list");
+
+	if (!list_empty(&fl->fl_link))
+		panic("Attempting to free lock on active lock list");
+
+	if (fl->fl_ops) {
+		if (fl->fl_ops->fl_release_private)
+			fl->fl_ops->fl_release_private(fl);
+		fl->fl_ops = NULL;
+	}
+
+	if (fl->fl_lmops) {
+		if (fl->fl_lmops->fl_release_private)
+			fl->fl_lmops->fl_release_private(fl);
+		fl->fl_lmops = NULL;
+	}
+
+	kmem_cache_free(filelock_cache, fl);
+}
+
+void locks_init_lock(struct file_lock *fl)
+{
+	INIT_LIST_HEAD(&fl->fl_link);
+	INIT_LIST_HEAD(&fl->fl_block);
+	init_waitqueue_head(&fl->fl_wait);
+	fl->fl_next = NULL;
+	fl->fl_fasync = NULL;
+	fl->fl_owner = NULL;
+	fl->fl_pid = 0;
+	fl->fl_file = NULL;
+	fl->fl_flags = 0;
+	fl->fl_type = 0;
+	fl->fl_start = fl->fl_end = 0;
+	fl->fl_ops = NULL;
+	fl->fl_lmops = NULL;
+}
+
+EXPORT_SYMBOL(locks_init_lock);
+
+/*
+ * Initialises the fields of the file lock which are invariant for
+ * free file_locks.
+ */
+static void init_once(void *foo, kmem_cache_t *cache, unsigned long flags)
+{
+	struct file_lock *lock = (struct file_lock *) foo;
+
+	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) !=
+					SLAB_CTOR_CONSTRUCTOR)
+		return;
+
+	locks_init_lock(lock);
+}
+
+/*
+ * Initialize a new lock from an existing file_lock structure.
+ */
+void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
+{
+	new->fl_owner = fl->fl_owner;
+	new->fl_pid = fl->fl_pid;
+	new->fl_file = fl->fl_file;
+	new->fl_flags = fl->fl_flags;
+	new->fl_type = fl->fl_type;
+	new->fl_start = fl->fl_start;
+	new->fl_end = fl->fl_end;
+	new->fl_ops = fl->fl_ops;
+	new->fl_lmops = fl->fl_lmops;
+	if (fl->fl_ops && fl->fl_ops->fl_copy_lock)
+		fl->fl_ops->fl_copy_lock(new, fl);
+	if (fl->fl_lmops && fl->fl_lmops->fl_copy_lock)
+		fl->fl_lmops->fl_copy_lock(new, fl);
+}
+
+EXPORT_SYMBOL(locks_copy_lock);
+
+static inline int flock_translate_cmd(int cmd) {
+	if (cmd & LOCK_MAND)
+		return cmd & (LOCK_MAND | LOCK_RW);
+	switch (cmd) {
+	case LOCK_SH:
+		return F_RDLCK;
+	case LOCK_EX:
+		return F_WRLCK;
+	case LOCK_UN:
+		return F_UNLCK;
+	}
+	return -EINVAL;
+}
+
+/* Fill in a file_lock structure with an appropriate FLOCK lock. */
+static int flock_make_lock(struct file *filp, struct file_lock **lock,
+		unsigned int cmd)
+{
+	struct file_lock *fl;
+	int type = flock_translate_cmd(cmd);
+	if (type < 0)
+		return type;
+	
+	fl = locks_alloc_lock();
+	if (fl == NULL)
+		return -ENOMEM;
+
+	fl->fl_file = filp;
+	fl->fl_pid = current->tgid;
+	fl->fl_flags = FL_FLOCK;
+	fl->fl_type = type;
+	fl->fl_end = OFFSET_MAX;
+	
+	*lock = fl;
+	return 0;
+}
+
+static int assign_type(struct file_lock *fl, int type)
+{
+	switch (type) {
+	case F_RDLCK:
+	case F_WRLCK:
+	case F_UNLCK:
+		fl->fl_type = type;
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
+ * style lock.
+ */
+static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
+			       struct flock *l)
+{
+	off_t start, end;
+
+	switch (l->l_whence) {
+	case 0: /*SEEK_SET*/
+		start = 0;
+		break;
+	case 1: /*SEEK_CUR*/
+		start = filp->f_pos;
+		break;
+	case 2: /*SEEK_END*/
+		start = i_size_read(filp->f_dentry->d_inode);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* POSIX-1996 leaves the case l->l_len < 0 undefined;
+	   POSIX-2001 defines it. */
+	start += l->l_start;
+	end = start + l->l_len - 1;
+	if (l->l_len < 0) {
+		end = start - 1;
+		start += l->l_len;
+	}
+
+	if (start < 0)
+		return -EINVAL;
+	if (l->l_len > 0 && end < 0)
+		return -EOVERFLOW;
+
+	fl->fl_start = start;	/* we record the absolute position */
+	fl->fl_end = end;
+	if (l->l_len == 0)
+		fl->fl_end = OFFSET_MAX;
+	
+	fl->fl_owner = current->files;
+	fl->fl_pid = current->tgid;
+	fl->fl_file = filp;
+	fl->fl_flags = FL_POSIX;
+	fl->fl_ops = NULL;
+	fl->fl_lmops = NULL;
+
+	return assign_type(fl, l->l_type);
+}
+
+#if BITS_PER_LONG == 32
+static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
+				 struct flock64 *l)
+{
+	loff_t start;
+
+	switch (l->l_whence) {
+	case 0: /*SEEK_SET*/
+		start = 0;
+		break;
+	case 1: /*SEEK_CUR*/
+		start = filp->f_pos;
+		break;
+	case 2: /*SEEK_END*/
+		start = i_size_read(filp->f_dentry->d_inode);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (((start += l->l_start) < 0) || (l->l_len < 0))
+		return -EINVAL;
+	fl->fl_end = start + l->l_len - 1;
+	if (l->l_len > 0 && fl->fl_end < 0)
+		return -EOVERFLOW;
+	fl->fl_start = start;	/* we record the absolute position */
+	if (l->l_len == 0)
+		fl->fl_end = OFFSET_MAX;
+	
+	fl->fl_owner = current->files;
+	fl->fl_pid = current->tgid;
+	fl->fl_file = filp;
+	fl->fl_flags = FL_POSIX;
+	fl->fl_ops = NULL;
+	fl->fl_lmops = NULL;
+
+	switch (l->l_type) {
+	case F_RDLCK:
+	case F_WRLCK:
+	case F_UNLCK:
+		fl->fl_type = l->l_type;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return (0);
+}
+#endif
+
+/* default lease lock manager operations */
+static void lease_break_callback(struct file_lock *fl)
+{
+	kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
+}
+
+static void lease_release_private_callback(struct file_lock *fl)
+{
+	if (!fl->fl_file)
+		return;
+
+	f_delown(fl->fl_file);
+	fl->fl_file->f_owner.signum = 0;
+}
+
+int lease_mylease_callback(struct file_lock *fl, struct file_lock *try)
+{
+	return fl->fl_file == try->fl_file;
+}
+
+struct lock_manager_operations lease_manager_ops = {
+	.fl_break = lease_break_callback,
+	.fl_release_private = lease_release_private_callback,
+	.fl_mylease = lease_mylease_callback,
+	.fl_change = lease_modify,
+};
+
+/*
+ * Initialize a lease, use the default lock manager operations
+ */
+static int lease_init(struct file *filp, int type, struct file_lock *fl)
+ {
+	fl->fl_owner = current->files;
+	fl->fl_pid = current->tgid;
+
+	fl->fl_file = filp;
+	fl->fl_flags = FL_LEASE;
+	if (assign_type(fl, type) != 0) {
+		locks_free_lock(fl);
+		return -EINVAL;
+	}
+	fl->fl_start = 0;
+	fl->fl_end = OFFSET_MAX;
+	fl->fl_ops = NULL;
+	fl->fl_lmops = &lease_manager_ops;
+	return 0;
+}
+
+/* Allocate a file_lock initialised to this type of lease */
+static int lease_alloc(struct file *filp, int type, struct file_lock **flp)
+{
+	struct file_lock *fl = locks_alloc_lock();
+	int error;
+
+	if (fl == NULL)
+		return -ENOMEM;
+
+	error = lease_init(filp, type, fl);
+	if (error)
+		return error;
+	*flp = fl;
+	return 0;
+}
+
+/* Check if two locks overlap each other.
+ */
+static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
+{
+	return ((fl1->fl_end >= fl2->fl_start) &&
+		(fl2->fl_end >= fl1->fl_start));
+}
+
+/*
+ * Check whether two locks have the same owner.
+ */
+static inline int
+posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
+{
+	if (fl1->fl_lmops && fl1->fl_lmops->fl_compare_owner)
+		return fl2->fl_lmops == fl1->fl_lmops &&
+			fl1->fl_lmops->fl_compare_owner(fl1, fl2);
+	return fl1->fl_owner == fl2->fl_owner;
+}
+
+/* Remove waiter from blocker's block list.
+ * When blocker ends up pointing to itself then the list is empty.
+ */
+static inline void __locks_delete_block(struct file_lock *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_kernel();
+	__locks_delete_block(waiter);
+	unlock_kernel();
+}
+
+/* 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.
+ */
+static void locks_insert_block(struct file_lock *blocker, 
+			       struct file_lock *waiter)
+{
+	if (!list_empty(&waiter->fl_block)) {
+		printk(KERN_ERR "locks_insert_block: removing duplicated lock "
+			"(pid=%d %Ld-%Ld type=%d)\n", waiter->fl_pid,
+			waiter->fl_start, waiter->fl_end, waiter->fl_type);
+		__locks_delete_block(waiter);
+	}
+	list_add_tail(&waiter->fl_block, &blocker->fl_block);
+	waiter->fl_next = blocker;
+	if (IS_POSIX(blocker))
+		list_add(&waiter->fl_link, &blocked_list);
+}
+
+/* Wake up processes blocked waiting for blocker.
+ * If told to wait then schedule the processes until the block list
+ * is empty, otherwise empty the block list ourselves.
+ */
+static void locks_wake_up_blocks(struct file_lock *blocker)
+{
+	while (!list_empty(&blocker->fl_block)) {
+		struct file_lock *waiter = list_entry(blocker->fl_block.next,
+				struct file_lock, fl_block);
+		__locks_delete_block(waiter);
+		if (waiter->fl_lmops && waiter->fl_lmops->fl_notify)
+			waiter->fl_lmops->fl_notify(waiter);
+		else
+			wake_up(&waiter->fl_wait);
+	}
+}
+
+/* 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.
+ */
+static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
+{
+	list_add(&fl->fl_link, &file_lock_list);
+
+	/* insert into file's list */
+	fl->fl_next = *pos;
+	*pos = fl;
+
+	if (fl->fl_ops && fl->fl_ops->fl_insert)
+		fl->fl_ops->fl_insert(fl);
+}
+
+/*
+ * Delete a lock and then free it.
+ * Wake up processes that are blocked waiting for this lock,
+ * notify the FS that the lock has been cleared and
+ * finally free the lock.
+ */
+static void locks_delete_lock(struct file_lock **thisfl_p)
+{
+	struct file_lock *fl = *thisfl_p;
+
+	*thisfl_p = fl->fl_next;
+	fl->fl_next = NULL;
+	list_del_init(&fl->fl_link);
+
+	fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
+	if (fl->fl_fasync != NULL) {
+		printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
+		fl->fl_fasync = NULL;
+	}
+
+	if (fl->fl_ops && fl->fl_ops->fl_remove)
+		fl->fl_ops->fl_remove(fl);
+
+	locks_wake_up_blocks(fl);
+	locks_free_lock(fl);
+}
+
+/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
+ * checks for shared/exclusive status of overlapping locks.
+ */
+static int locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
+{
+	if (sys_fl->fl_type == F_WRLCK)
+		return 1;
+	if (caller_fl->fl_type == F_WRLCK)
+		return 1;
+	return 0;
+}
+
+/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
+ * checking before calling the locks_conflict().
+ */
+static int posix_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
+{
+	/* POSIX locks owned by the same process do not conflict with
+	 * each other.
+	 */
+	if (!IS_POSIX(sys_fl) || posix_same_owner(caller_fl, sys_fl))
+		return (0);
+
+	/* Check whether they overlap */
+	if (!locks_overlap(caller_fl, sys_fl))
+		return 0;
+
+	return (locks_conflict(caller_fl, sys_fl));
+}
+
+/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
+ * checking before calling the locks_conflict().
+ */
+static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl)
+{
+	/* FLOCK locks referring to the same filp do not conflict with
+	 * each other.
+	 */
+	if (!IS_FLOCK(sys_fl) || (caller_fl->fl_file == sys_fl->fl_file))
+		return (0);
+	if ((caller_fl->fl_type & LOCK_MAND) || (sys_fl->fl_type & LOCK_MAND))
+		return 0;
+
+	return (locks_conflict(caller_fl, sys_fl));
+}
+
+static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout)
+{
+	int result = 0;
+	DECLARE_WAITQUEUE(wait, current);
+
+	__set_current_state(TASK_INTERRUPTIBLE);
+	add_wait_queue(fl_wait, &wait);
+	if (timeout == 0)
+		schedule();
+	else
+		result = schedule_timeout(timeout);
+	if (signal_pending(current))
+		result = -ERESTARTSYS;
+	remove_wait_queue(fl_wait, &wait);
+	__set_current_state(TASK_RUNNING);
+	return result;
+}
+
+static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *waiter, int time)
+{
+	int result;
+	locks_insert_block(blocker, waiter);
+	result = interruptible_sleep_on_locked(&waiter->fl_wait, time);
+	__locks_delete_block(waiter);
+	return result;
+}
+
+struct file_lock *
+posix_test_lock(struct file *filp, struct file_lock *fl)
+{
+	struct file_lock *cfl;
+
+	lock_kernel();
+	for (cfl = filp->f_dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
+		if (!IS_POSIX(cfl))
+			continue;
+		if (posix_locks_conflict(cfl, fl))
+			break;
+	}
+	unlock_kernel();
+
+	return (cfl);
+}
+
+EXPORT_SYMBOL(posix_test_lock);
+
+/* This function tests for deadlock condition before putting a process to
+ * sleep. The detection scheme is no longer recursive. Recursive was neat,
+ * but dangerous - we risked stack corruption if the lock data was bad, or
+ * if the recursion was too deep for any other reason.
+ *
+ * We rely on the fact that a task can only be on one lock's wait queue
+ * at a time. When we find blocked_task on a wait queue we can re-search
+ * with blocked_task equal to that queue's owner, until either blocked_task
+ * isn't found, or blocked_task is found on a queue owned by my_task.
+ *
+ * Note: the above assumption may not be true when handling lock requests
+ * from a broken NFS client. But broken NFS clients have a lot more to
+ * worry about than proper deadlock detection anyway... --okir
+ */
+int posix_locks_deadlock(struct file_lock *caller_fl,
+				struct file_lock *block_fl)
+{
+	struct list_head *tmp;
+
+next_task:
+	if (posix_same_owner(caller_fl, block_fl))
+		return 1;
+	list_for_each(tmp, &blocked_list) {
+		struct file_lock *fl = list_entry(tmp, struct file_lock, fl_link);
+		if (posix_same_owner(fl, block_fl)) {
+			fl = fl->fl_next;
+			block_fl = fl;
+			goto next_task;
+		}
+	}
+	return 0;
+}
+
+EXPORT_SYMBOL(posix_locks_deadlock);
+
+/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
+ * at the head of the list, but that's secret knowledge known only to
+ * flock_lock_file and posix_lock_file.
+ */
+static int flock_lock_file(struct file *filp, struct file_lock *new_fl)
+{
+	struct file_lock **before;
+	struct inode * inode = filp->f_dentry->d_inode;
+	int error = 0;
+	int found = 0;
+
+	lock_kernel();
+	for_each_lock(inode, before) {
+		struct file_lock *fl = *before;
+		if (IS_POSIX(fl))
+			break;
+		if (IS_LEASE(fl))
+			continue;
+		if (filp != fl->fl_file)
+			continue;
+		if (new_fl->fl_type == fl->fl_type)
+			goto out;
+		found = 1;
+		locks_delete_lock(before);
+		break;
+	}
+	unlock_kernel();
+
+	if (new_fl->fl_type == F_UNLCK)
+		return 0;
+
+	/*
+	 * If a higher-priority process was blocked on the old file lock,
+	 * give it the opportunity to lock the file.
+	 */
+	if (found)
+		cond_resched();
+
+	lock_kernel();
+	for_each_lock(inode, before) {
+		struct file_lock *fl = *before;
+		if (IS_POSIX(fl))
+			break;
+		if (IS_LEASE(fl))
+			continue;
+		if (!flock_locks_conflict(new_fl, fl))
+			continue;
+		error = -EAGAIN;
+		if (new_fl->fl_flags & FL_SLEEP) {
+			locks_insert_block(fl, new_fl);
+		}
+		goto out;
+	}
+	locks_insert_lock(&inode->i_flock, new_fl);
+	error = 0;
+
+out:
+	unlock_kernel();
+	return error;
+}
+
+EXPORT_SYMBOL(posix_lock_file);
+
+static int __posix_lock_file(struct inode *inode, struct file_lock *request)
+{
+	struct file_lock *fl;
+	struct file_lock *new_fl, *new_fl2;
+	struct file_lock *left = NULL;
+	struct file_lock *right = NULL;
+	struct file_lock **before;
+	int error, added = 0;
+
+	/*
+	 * We may need two file_lock structures for this operation,
+	 * so we get them in advance to avoid races.
+	 */
+	new_fl = locks_alloc_lock();
+	new_fl2 = locks_alloc_lock();
+
+	lock_kernel();
+	if (request->fl_type != F_UNLCK) {
+		for_each_lock(inode, before) {
+			struct file_lock *fl = *before;
+			if (!IS_POSIX(fl))
+				continue;
+			if (!posix_locks_conflict(request, fl))
+				continue;
+			error = -EAGAIN;
+			if (!(request->fl_flags & FL_SLEEP))
+				goto out;
+			error = -EDEADLK;
+			if (posix_locks_deadlock(request, fl))
+				goto out;
+			error = -EAGAIN;
+			locks_insert_block(fl, request);
+			goto out;
+  		}
+  	}
+
+	/* If we're just looking for a conflict, we're done. */
+	error = 0;
+	if (request->fl_flags & FL_ACCESS)
+		goto out;
+
+	error = -ENOLCK; /* "no luck" */
+	if (!(new_fl && new_fl2))
+		goto out;
+
+	/*
+	 * We've allocated the new locks in advance, so there are no
+	 * errors possible (and no blocking operations) from here on.
+	 * 
+	 * Find the first old lock with the same owner as the new lock.
+	 */
+	
+	before = &inode->i_flock;
+
+	/* First skip locks owned by other processes.  */
+	while ((fl = *before) && (!IS_POSIX(fl) ||
+				  !posix_same_owner(request, fl))) {
+		before = &fl->fl_next;
+	}
+
+	/* Process locks with this owner.  */
+	while ((fl = *before) && posix_same_owner(request, fl)) {
+		/* Detect adjacent or overlapping regions (if same lock type)
+		 */
+		if (request->fl_type == fl->fl_type) {
+			if (fl->fl_end < request->fl_start - 1)
+				goto next_lock;
+			/* If the next lock in the list has entirely bigger
+			 * addresses than the new one, insert the lock here.
+			 */
+			if (fl->fl_start > request->fl_end + 1)
+				break;
+
+			/* If we come here, the new and old lock are of the
+			 * same type and adjacent or overlapping. Make one
+			 * lock yielding from the lower start address of both
+			 * locks to the higher end address.
+			 */
+			if (fl->fl_start > request->fl_start)
+				fl->fl_start = request->fl_start;
+			else
+				request->fl_start = fl->fl_start;
+			if (fl->fl_end < request->fl_end)
+				fl->fl_end = request->fl_end;
+			else
+				request->fl_end = fl->fl_end;
+			if (added) {
+				locks_delete_lock(before);
+				continue;
+			}
+			request = fl;
+			added = 1;
+		}
+		else {
+			/* Processing for different lock types is a bit
+			 * more complex.
+			 */
+			if (fl->fl_end < request->fl_start)
+				goto next_lock;
+			if (fl->fl_start > request->fl_end)
+				break;
+			if (request->fl_type == F_UNLCK)
+				added = 1;
+			if (fl->fl_start < request->fl_start)
+				left = fl;
+			/* If the next lock in the list has a higher end
+			 * address than the new one, insert the new one here.
+			 */
+			if (fl->fl_end > request->fl_end) {
+				right = fl;
+				break;
+			}
+			if (fl->fl_start >= request->fl_start) {
+				/* The new lock completely replaces an old
+				 * one (This may happen several times).
+				 */
+				if (added) {
+					locks_delete_lock(before);
+					continue;
+				}
+				/* Replace the old lock with the new one.
+				 * Wake up anybody waiting for the old one,
+				 * as the change in lock type might satisfy
+				 * their needs.
+				 */
+				locks_wake_up_blocks(fl);
+				fl->fl_start = request->fl_start;
+				fl->fl_end = request->fl_end;
+				fl->fl_type = request->fl_type;
+				fl->fl_u = request->fl_u;
+				request = fl;
+				added = 1;
+			}
+		}
+		/* Go on to next lock.
+		 */
+	next_lock:
+		before = &fl->fl_next;
+	}
+
+	error = 0;
+	if (!added) {
+		if (request->fl_type == F_UNLCK)
+			goto out;
+		locks_copy_lock(new_fl, request);
+		locks_insert_lock(before, new_fl);
+		new_fl = NULL;
+	}
+	if (right) {
+		if (left == right) {
+			/* The new lock breaks the old one in two pieces,
+			 * so we have to use the second new lock.
+			 */
+			left = new_fl2;
+			new_fl2 = NULL;
+			locks_copy_lock(left, right);
+			locks_insert_lock(before, left);
+		}
+		right->fl_start = request->fl_end + 1;
+		locks_wake_up_blocks(right);
+	}
+	if (left) {
+		left->fl_end = request->fl_start - 1;
+		locks_wake_up_blocks(left);
+	}
+ out:
+	unlock_kernel();
+	/*
+	 * Free any unused locks.
+	 */
+	if (new_fl)
+		locks_free_lock(new_fl);
+	if (new_fl2)
+		locks_free_lock(new_fl2);
+	return error;
+}
+
+/**
+ * posix_lock_file - Apply a POSIX-style lock to a file
+ * @filp: The file to apply the lock to
+ * @fl: The lock to be applied
+ *
+ * Add a POSIX style lock to a file.
+ * We merge adjacent & overlapping locks whenever possible.
+ * POSIX locks are sorted by owner task, then by starting address
+ */
+int posix_lock_file(struct file *filp, struct file_lock *fl)
+{
+	return __posix_lock_file(filp->f_dentry->d_inode, fl);
+}
+
+/**
+ * posix_lock_file_wait - Apply a POSIX-style lock to a file
+ * @filp: The file to apply the lock to
+ * @fl: The lock to be applied
+ *
+ * Add a POSIX style lock to a file.
+ * We merge adjacent & overlapping locks whenever possible.
+ * POSIX locks are sorted by owner task, then by starting address
+ */
+int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
+{
+	int error;
+	might_sleep ();
+	for (;;) {
+		error = __posix_lock_file(filp->f_dentry->d_inode, fl);
+		if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP))
+			break;
+		error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
+		if (!error)
+			continue;
+
+		locks_delete_block(fl);
+		break;
+	}
+	return error;
+}
+EXPORT_SYMBOL(posix_lock_file_wait);
+
+/**
+ * locks_mandatory_locked - Check for an active lock
+ * @inode: the file to check
+ *
+ * Searches the inode's list of locks to find any POSIX locks which conflict.
+ * This function is called from locks_verify_locked() only.
+ */
+int locks_mandatory_locked(struct inode *inode)
+{
+	fl_owner_t owner = current->files;
+	struct file_lock *fl;
+
+	/*
+	 * Search the lock list for this inode for any POSIX locks.
+	 */
+	lock_kernel();
+	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
+		if (!IS_POSIX(fl))
+			continue;
+		if (fl->fl_owner != owner)
+			break;
+	}
+	unlock_kernel();
+	return fl ? -EAGAIN : 0;
+}
+
+/**
+ * locks_mandatory_area - Check for a conflicting lock
+ * @read_write: %FLOCK_VERIFY_WRITE for exclusive access, %FLOCK_VERIFY_READ
+ *		for shared
+ * @inode:      the file to check
+ * @filp:       how the file was opened (if it was)
+ * @offset:     start of area to check
+ * @count:      length of area to check
+ *
+ * Searches the inode's list of locks to find any POSIX locks which conflict.
+ * This function is called from rw_verify_area() and
+ * locks_verify_truncate().
+ */
+int locks_mandatory_area(int read_write, struct inode *inode,
+			 struct file *filp, loff_t offset,
+			 size_t count)
+{
+	struct file_lock fl;
+	int error;
+
+	locks_init_lock(&fl);
+	fl.fl_owner = current->files;
+	fl.fl_pid = current->tgid;
+	fl.fl_file = filp;
+	fl.fl_flags = FL_POSIX | FL_ACCESS;
+	if (filp && !(filp->f_flags & O_NONBLOCK))
+		fl.fl_flags |= FL_SLEEP;
+	fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
+	fl.fl_start = offset;
+	fl.fl_end = offset + count - 1;
+
+	for (;;) {
+		error = __posix_lock_file(inode, &fl);
+		if (error != -EAGAIN)
+			break;
+		if (!(fl.fl_flags & FL_SLEEP))
+			break;
+		error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
+		if (!error) {
+			/*
+			 * If we've been sleeping someone might have
+			 * changed the permissions behind our back.
+			 */
+			if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)
+				continue;
+		}
+
+		locks_delete_block(&fl);
+		break;
+	}
+
+	return error;
+}
+
+EXPORT_SYMBOL(locks_mandatory_area);
+
+/* We already had a lease on this file; just change its type */
+int lease_modify(struct file_lock **before, int arg)
+{
+	struct file_lock *fl = *before;
+	int error = assign_type(fl, arg);
+
+	if (error)
+		return error;
+	locks_wake_up_blocks(fl);
+	if (arg == F_UNLCK)
+		locks_delete_lock(before);
+	return 0;
+}
+
+EXPORT_SYMBOL(lease_modify);
+
+static void time_out_leases(struct inode *inode)
+{
+	struct file_lock **before;
+	struct file_lock *fl;
+
+	before = &inode->i_flock;
+	while ((fl = *before) && IS_LEASE(fl) && (fl->fl_type & F_INPROGRESS)) {
+		if ((fl->fl_break_time == 0)
+				|| time_before(jiffies, fl->fl_break_time)) {
+			before = &fl->fl_next;
+			continue;
+		}
+		printk(KERN_INFO "lease broken - owner pid = %d\n", fl->fl_pid);
+		lease_modify(before, fl->fl_type & ~F_INPROGRESS);
+		if (fl == *before)	/* lease_modify may have freed fl */
+			before = &fl->fl_next;
+	}
+}
+
+/**
+ *	__break_lease	-	revoke all outstanding leases on file
+ *	@inode: the inode of the file to return
+ *	@mode: the open mode (read or write)
+ *
+ *	break_lease (inlined for speed) has checked there already
+ *	is a lease on this file.  Leases are broken on a call to open()
+ *	or truncate().  This function can sleep unless you
+ *	specified %O_NONBLOCK to your open().
+ */
+int __break_lease(struct inode *inode, unsigned int mode)
+{
+	int error = 0, future;
+	struct file_lock *new_fl, *flock;
+	struct file_lock *fl;
+	int alloc_err;
+	unsigned long break_time;
+	int i_have_this_lease = 0;
+
+	alloc_err = lease_alloc(NULL, mode & FMODE_WRITE ? F_WRLCK : F_RDLCK,
+			&new_fl);
+
+	lock_kernel();
+
+	time_out_leases(inode);
+
+	flock = inode->i_flock;
+	if ((flock == NULL) || !IS_LEASE(flock))
+		goto out;
+
+	for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
+		if (fl->fl_owner == current->files)
+			i_have_this_lease = 1;
+
+	if (mode & FMODE_WRITE) {
+		/* If we want write access, we have to revoke any lease. */
+		future = F_UNLCK | F_INPROGRESS;
+	} else if (flock->fl_type & F_INPROGRESS) {
+		/* If the lease is already being broken, we just leave it */
+		future = flock->fl_type;
+	} else if (flock->fl_type & F_WRLCK) {
+		/* Downgrade the exclusive lease to a read-only lease. */
+		future = F_RDLCK | F_INPROGRESS;
+	} else {
+		/* the existing lease was read-only, so we can read too. */
+		goto out;
+	}