Merge branch 'locks' of git://linux-nfs.org/~bfields/linux
* 'locks' of git://linux-nfs.org/~bfields/linux: pid-namespaces-vs-locks-interaction file locks: Use wait_event_interruptible_timeout() locks: clarify posix_locks_deadlock
This commit is contained in:
Linus Torvalds
Коммит
9853832c49
125
fs/locks.c
125
fs/locks.c
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@ -125,6 +125,7 @@
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#include <linux/syscalls.h>
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#include <linux/time.h>
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#include <linux/rcupdate.h>
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#include <linux/pid_namespace.h>
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#include <asm/semaphore.h>
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#include <asm/uaccess.h>
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@ -185,6 +186,7 @@ void locks_init_lock(struct file_lock *fl)
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fl->fl_fasync = NULL;
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fl->fl_owner = NULL;
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fl->fl_pid = 0;
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fl->fl_nspid = NULL;
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fl->fl_file = NULL;
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fl->fl_flags = 0;
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fl->fl_type = 0;
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@ -553,6 +555,8 @@ static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
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{
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list_add(&fl->fl_link, &file_lock_list);
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fl->fl_nspid = get_pid(task_tgid(current));
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/* insert into file's list */
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fl->fl_next = *pos;
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*pos = fl;
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@ -584,6 +588,11 @@ static void locks_delete_lock(struct file_lock **thisfl_p)
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if (fl->fl_ops && fl->fl_ops->fl_remove)
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fl->fl_ops->fl_remove(fl);
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if (fl->fl_nspid) {
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put_pid(fl->fl_nspid);
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fl->fl_nspid = NULL;
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}
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locks_wake_up_blocks(fl);
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locks_free_lock(fl);
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}
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@ -634,33 +643,6 @@ static int flock_locks_conflict(struct file_lock *caller_fl, struct file_lock *s
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return (locks_conflict(caller_fl, sys_fl));
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}
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static int interruptible_sleep_on_locked(wait_queue_head_t *fl_wait, int timeout)
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{
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int result = 0;
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DECLARE_WAITQUEUE(wait, current);
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__set_current_state(TASK_INTERRUPTIBLE);
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add_wait_queue(fl_wait, &wait);
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if (timeout == 0)
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schedule();
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else
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result = schedule_timeout(timeout);
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if (signal_pending(current))
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result = -ERESTARTSYS;
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remove_wait_queue(fl_wait, &wait);
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__set_current_state(TASK_RUNNING);
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return result;
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}
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static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *waiter, int time)
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{
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int result;
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locks_insert_block(blocker, waiter);
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result = interruptible_sleep_on_locked(&waiter->fl_wait, time);
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__locks_delete_block(waiter);
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return result;
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}
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void
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posix_test_lock(struct file *filp, struct file_lock *fl)
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{
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@ -673,55 +655,67 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
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if (posix_locks_conflict(fl, cfl))
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break;
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}
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if (cfl)
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if (cfl) {
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__locks_copy_lock(fl, cfl);
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else
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if (cfl->fl_nspid)
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fl->fl_pid = pid_nr_ns(cfl->fl_nspid,
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task_active_pid_ns(current));
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} else
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fl->fl_type = F_UNLCK;
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unlock_kernel();
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return;
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}
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EXPORT_SYMBOL(posix_test_lock);
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/* This function tests for deadlock condition before putting a process to
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* sleep. The detection scheme is no longer recursive. Recursive was neat,
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* but dangerous - we risked stack corruption if the lock data was bad, or
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* if the recursion was too deep for any other reason.
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/*
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* Deadlock detection:
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*
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* We rely on the fact that a task can only be on one lock's wait queue
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* at a time. When we find blocked_task on a wait queue we can re-search
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* with blocked_task equal to that queue's owner, until either blocked_task
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* isn't found, or blocked_task is found on a queue owned by my_task.
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* We attempt to detect deadlocks that are due purely to posix file
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* locks.
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*
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* Note: the above assumption may not be true when handling lock requests
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* from a broken NFS client. But broken NFS clients have a lot more to
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* worry about than proper deadlock detection anyway... --okir
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* We assume that a task can be waiting for at most one lock at a time.
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* So for any acquired lock, the process holding that lock may be
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* waiting on at most one other lock. That lock in turns may be held by
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* someone waiting for at most one other lock. Given a requested lock
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* caller_fl which is about to wait for a conflicting lock block_fl, we
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* follow this chain of waiters to ensure we are not about to create a
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* cycle.
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*
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* However, the failure of this assumption (also possible in the case of
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* multiple tasks sharing the same open file table) also means there's no
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* guarantee that the loop below will terminate. As a hack, we give up
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* after a few iterations.
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* Since we do this before we ever put a process to sleep on a lock, we
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* are ensured that there is never a cycle; that is what guarantees that
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* the while() loop in posix_locks_deadlock() eventually completes.
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*
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* Note: the above assumption may not be true when handling lock
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* requests from a broken NFS client. It may also fail in the presence
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* of tasks (such as posix threads) sharing the same open file table.
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*
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* To handle those cases, we just bail out after a few iterations.
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*/
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#define MAX_DEADLK_ITERATIONS 10
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/* Find a lock that the owner of the given block_fl is blocking on. */
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static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
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{
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struct file_lock *fl;
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list_for_each_entry(fl, &blocked_list, fl_link) {
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if (posix_same_owner(fl, block_fl))
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return fl->fl_next;
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}
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return NULL;
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}
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static int posix_locks_deadlock(struct file_lock *caller_fl,
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struct file_lock *block_fl)
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{
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struct file_lock *fl;
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int i = 0;
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next_task:
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if (posix_same_owner(caller_fl, block_fl))
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return 1;
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list_for_each_entry(fl, &blocked_list, fl_link) {
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if (posix_same_owner(fl, block_fl)) {
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if (i++ > MAX_DEADLK_ITERATIONS)
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return 0;
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fl = fl->fl_next;
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block_fl = fl;
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goto next_task;
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}
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while ((block_fl = what_owner_is_waiting_for(block_fl))) {
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if (i++ > MAX_DEADLK_ITERATIONS)
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return 0;
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if (posix_same_owner(caller_fl, block_fl))
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return 1;
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}
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return 0;
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}
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@ -1256,7 +1250,10 @@ restart:
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if (break_time == 0)
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break_time++;
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}
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error = locks_block_on_timeout(flock, new_fl, break_time);
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locks_insert_block(flock, new_fl);
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error = wait_event_interruptible_timeout(new_fl->fl_wait,
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!new_fl->fl_next, break_time);
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__locks_delete_block(new_fl);
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if (error >= 0) {
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if (error == 0)
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time_out_leases(inode);
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@ -2084,6 +2081,12 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
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int id, char *pfx)
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{
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struct inode *inode = NULL;
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unsigned int fl_pid;
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if (fl->fl_nspid)
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fl_pid = pid_nr_ns(fl->fl_nspid, task_active_pid_ns(current));
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else
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fl_pid = fl->fl_pid;
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if (fl->fl_file != NULL)
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inode = fl->fl_file->f_path.dentry->d_inode;
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@ -2124,16 +2127,16 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
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}
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if (inode) {
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#ifdef WE_CAN_BREAK_LSLK_NOW
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seq_printf(f, "%d %s:%ld ", fl->fl_pid,
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seq_printf(f, "%d %s:%ld ", fl_pid,
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inode->i_sb->s_id, inode->i_ino);
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#else
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/* userspace relies on this representation of dev_t ;-( */
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seq_printf(f, "%d %02x:%02x:%ld ", fl->fl_pid,
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seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
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MAJOR(inode->i_sb->s_dev),
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MINOR(inode->i_sb->s_dev), inode->i_ino);
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#endif
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} else {
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seq_printf(f, "%d <none>:0 ", fl->fl_pid);
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seq_printf(f, "%d <none>:0 ", fl_pid);
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}
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if (IS_POSIX(fl)) {
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if (fl->fl_end == OFFSET_MAX)
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@ -872,6 +872,7 @@ struct file_lock {
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struct list_head fl_block; /* circular list of blocked processes */
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fl_owner_t fl_owner;
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unsigned int fl_pid;
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struct pid *fl_nspid;
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wait_queue_head_t fl_wait;
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struct file *fl_file;
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unsigned char fl_flags;
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