trace_locks_get_lock

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  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/filesystems/mandatory-locking.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.
 *
 * Locking conflicts and dependencies:
 * If multiple threads attempt to lock the same byte (or flock the same file)
 * only one can be granted the lock, and other must wait their turn.
 * The first lock has been "applied" or "granted", the others are "waiting"
 * and are "blocked" by the "applied" lock..
 *
 * Waiting and applied locks are all kept in trees whose properties are:
 *
 *  - the root of a tree may be an applied or waiting lock.
 *  - every other node in the tree is a waiting lock that
 *    conflicts with every ancestor of that node.
 *
 * Every such tree begins life as a waiting singleton which obviously
 * satisfies the above properties.
 *
 * The only ways we modify trees preserve these properties:
 *
 *  1. We may add a new leaf node, but only after first verifying that it
 *     conflicts with all of its ancestors.
 *  2. We may remove the root of a tree, creating a new singleton
 *     tree from the root and N new trees rooted in the immediate
 *     children.
 *  3. If the root of a tree is not currently an applied lock, we may
 *     apply it (if possible).
 *  4. We may upgrade the root of the tree (either extend its range,
 *     or upgrade its entire range from read to write).
 *
 * When an applied lock is modified in a way that reduces or downgrades any
 * part of its range, we remove all its children (2 above).  This particularly
 * happens when a lock is unlocked.
 *
 * For each of those child trees we "wake up" the thread which is
 * waiting for the lock so it can continue handling as follows: if the
 * root of the tree applies, we do so (3).  If it doesn't, it must
 * conflict with some applied lock.  We remove (wake up) all of its children
 * (2), and add it is a new leaf to the tree rooted in the applied
 * lock (1).  We then repeat the process recursively with those
 * children.
 *
 */
 
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/time.h>
#include <linux/rcupdate.h>
#include <linux/pid_namespace.h>
#include <linux/hashtable.h>
#include <linux/percpu.h>
 
#define CREATE_TRACE_POINTS
#include <trace/events/filelock.h>
/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Events for filesystem locks
 *
 * Copyright 2013 Jeff Layton <jlayton@poochiereds.net>
 */
#undef TRACE_SYSTEM
#define TRACE_SYSTEM filelock
 
#if !defined(_TRACE_FILELOCK_H) || defined(TRACE_HEADER_MULTI_READ)
#define _TRACE_FILELOCK_H
 
#include <linux/tracepoint.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/kdev_t.h>
 
#define show_fl_flags(val)                      \
    __print_flags(val, "|",                     \
        { FL_POSIX,     "FL_POSIX" },           \
        { FL_FLOCK,     "FL_FLOCK" },           \
        { FL_DELEG,     "FL_DELEG" },           \
        { FL_ACCESS,        "FL_ACCESS" },          \
        { FL_EXISTS,        "FL_EXISTS" },          \
        { FL_LEASE,     "FL_LEASE" },           \
        { FL_CLOSE,     "FL_CLOSE" },           \
        { FL_SLEEP,     "FL_SLEEP" },           \
        { FL_DOWNGRADE_PENDING, "FL_DOWNGRADE_PENDING" },   \
        { FL_UNLOCK_PENDING,    "FL_UNLOCK_PENDING" },      \
        { FL_OFDLCK,        "FL_OFDLCK" })
 
#define show_fl_type(val)               \
    __print_symbolic(val,               \
            { F_RDLCK, "F_RDLCK" },     \
            { F_WRLCK, "F_WRLCK" },     \
            { F_UNLCK, "F_UNLCK" })
 
TRACE_EVENT(locks_get_lock_context,
    TP_PROTO(struct inode *inode, int type, struct file_lock_context *ctx),
 
    TP_ARGS(inode, type, ctx),
 
    TP_STRUCT__entry(
        __field(unsigned long, i_ino)
        __field(dev_t, s_dev)
        __field(unsigned char, type)
        __field(struct file_lock_context *, ctx)
    ),
 
    TP_fast_assign(
        __entry->s_dev = inode->i_sb->s_dev;
        __entry->i_ino = inode->i_ino;
        __entry->type = type;
        __entry->ctx = ctx;
    ),
 
    TP_printk("dev=0x%x:0x%x ino=0x%lx type=%s ctx=%p",
          MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
          __entry->i_ino, show_fl_type(__entry->type), __entry->ctx)
);
函数源码
