/*
 * 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)
);

DECLARE_EVENT_CLASS(filelock_lock,
	TP_PROTO(struct inode *inode, struct file_lock *fl, int ret),

	TP_ARGS(inode, fl, ret),

	TP_STRUCT__entry(
		__field(struct file_lock *, fl)
		__field(unsigned long, i_ino)
		__field(dev_t, s_dev)
		__field(struct file_lock *, fl_next)
		__field(fl_owner_t, fl_owner)
		__field(unsigned int, fl_pid)
		__field(unsigned int, fl_flags)
		__field(unsigned char, fl_type)
		__field(loff_t, fl_start)
		__field(loff_t, fl_end)
		__field(int, ret)
	),

	TP_fast_assign(
		__entry->fl = fl ? fl : NULL;
		__entry->s_dev = inode->i_sb->s_dev;
		__entry->i_ino = inode->i_ino;
		__entry->fl_next = fl ? fl->fl_next : NULL;
		__entry->fl_owner = fl ? fl->fl_owner : NULL;
		__entry->fl_pid = fl ? fl->fl_pid : 0;
		__entry->fl_flags = fl ? fl->fl_flags : 0;
		__entry->fl_type = fl ? fl->fl_type : 0;
		__entry->fl_start = fl ? fl->fl_start : 0;
		__entry->fl_end = fl ? fl->fl_end : 0;
		__entry->ret = ret;
	),

	TP_printk("fl=0x%p dev=0x%x:0x%x ino=0x%lx fl_next=0x%p fl_owner=0x%p fl_pid=%u fl_flags=%s fl_type=%s fl_start=%lld fl_end=%lld ret=%d",
		__entry->fl, MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
		__entry->i_ino, __entry->fl_next, __entry->fl_owner,
		__entry->fl_pid, show_fl_flags(__entry->fl_flags),
		show_fl_type(__entry->fl_type),
		__entry->fl_start, __entry->fl_end, __entry->ret)
);

DEFINE_EVENT(filelock_lock, posix_lock_inode,
		TP_PROTO(struct inode *inode, struct file_lock *fl, int ret),
		TP_ARGS(inode, fl, ret));

DEFINE_EVENT(filelock_lock, fcntl_setlk,
		TP_PROTO(struct inode *inode, struct file_lock *fl, int ret),
		TP_ARGS(inode, fl, ret));

DEFINE_EVENT(filelock_lock, locks_remove_posix,
		TP_PROTO(struct inode *inode, struct file_lock *fl, int ret),
		TP_ARGS(inode, fl, ret));

DECLARE_EVENT_CLASS(filelock_lease,

	TP_PROTO(struct inode *inode, struct file_lock *fl),

	TP_ARGS(inode, fl),

	TP_STRUCT__entry(
		__field(struct file_lock *, fl)
		__field(unsigned long, i_ino)
		__field(dev_t, s_dev)
		__field(struct file_lock *, fl_next)
		__field(fl_owner_t, fl_owner)
		__field(unsigned int, fl_flags)
		__field(unsigned char, fl_type)
		__field(unsigned long, fl_break_time)
		__field(unsigned long, fl_downgrade_time)
	),

	TP_fast_assign(
		__entry->fl = fl ? fl : NULL;
		__entry->s_dev = inode->i_sb->s_dev;
		__entry->i_ino = inode->i_ino;
		__entry->fl_next = fl ? fl->fl_next : NULL;
		__entry->fl_owner = fl ? fl->fl_owner : NULL;
		__entry->fl_flags = fl ? fl->fl_flags : 0;
		__entry->fl_type = fl ? fl->fl_type : 0;
		__entry->fl_break_time = fl ? fl->fl_break_time : 0;
		__entry->fl_downgrade_time = fl ? fl->fl_downgrade_time : 0;
	),

	TP_printk("fl=0x%p dev=0x%x:0x%x ino=0x%lx fl_next=0x%p fl_owner=0x%p fl_flags=%s fl_type=%s fl_break_time=%lu fl_downgrade_time=%lu",
		__entry->fl, MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
		__entry->i_ino, __entry->fl_next, __entry->fl_owner,
		show_fl_flags(__entry->fl_flags),
		show_fl_type(__entry->fl_type),
		__entry->fl_break_time, __entry->fl_downgrade_time)
);

DEFINE_EVENT(filelock_lease, break_lease_noblock, TP_PROTO(struct inode *inode, struct file_lock *fl),
		TP_ARGS(inode, fl));

DEFINE_EVENT(filelock_lease, break_lease_block, TP_PROTO(struct inode *inode, struct file_lock *fl),
		TP_ARGS(inode, fl));

DEFINE_EVENT(filelock_lease, break_lease_unblock, TP_PROTO(struct inode *inode, struct file_lock *fl),
		TP_ARGS(inode, fl));

DEFINE_EVENT(filelock_lease, generic_delete_lease, TP_PROTO(struct inode *inode, struct file_lock *fl),
		TP_ARGS(inode, fl));

DEFINE_EVENT(filelock_lease, time_out_leases, TP_PROTO(struct inode *inode, struct file_lock *fl),
		TP_ARGS(inode, fl));

TRACE_EVENT(generic_add_lease,
	TP_PROTO(struct inode *inode, struct file_lock *fl),

	TP_ARGS(inode, fl),

	TP_STRUCT__entry(
		__field(unsigned long, i_ino)
		__field(int, wcount)
		__field(int, dcount)
		__field(int, icount)
		__field(dev_t, s_dev)
		__field(fl_owner_t, fl_owner)
		__field(unsigned int, fl_flags)
		__field(unsigned char, fl_type)
	),

	TP_fast_assign(
		__entry->s_dev = inode->i_sb->s_dev;
		__entry->i_ino = inode->i_ino;
		__entry->wcount = atomic_read(&inode->i_writecount);
		__entry->dcount = d_count(fl->fl_file->f_path.dentry);
		__entry->icount = atomic_read(&inode->i_count);
		__entry->fl_owner = fl ? fl->fl_owner : NULL;
		__entry->fl_flags = fl ? fl->fl_flags : 0;
		__entry->fl_type = fl ? fl->fl_type : 0;
	),

	TP_printk("dev=0x%x:0x%x ino=0x%lx wcount=%d dcount=%d icount=%d fl_owner=0x%p fl_flags=%s fl_type=%s",
		MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
		__entry->i_ino, __entry->wcount, __entry->dcount,
		__entry->icount, __entry->fl_owner,
		show_fl_flags(__entry->fl_flags),
		show_fl_type(__entry->fl_type))
);

#endif /* _TRACE_FILELOCK_H */

/* This part must be outside protection */
#include <trace/define_trace.h>
d by btrfs_wq_run_delayed_node.

The problem is caused by btrfs_wq_run_delayed_node() queuing more and more
works if the number of delayed items is above BTRFS_DELAYED_BACKGROUND. The
worker func (btrfs_async_run_delayed_root) processes at least
BTRFS_DELAYED_BATCH items (if they are present in the list). So, the machinery
works as expected while the list is almost empty. As soon as it is getting
bigger, worker func starts to process more than one item at a time, it takes
longer, and the chances to have async_works queued more than needed is getting
higher.

The problem above is worsened by another flaw of delayed-inode implementation:
if async_work was queued in a throttling branch (number of items &gt;=
BTRFS_DELAYED_WRITEBACK), corresponding worker func won't quit until
the number of items &lt; BTRFS_DELAYED_BACKGROUND / 2. So, it is possible that
the func occupies CPU infinitely (up to 30sec in my experiments): while the
func is trying to drain the list, the user activity may add more and more
items to the list.

The patch fixes both problems in straightforward way: refuse queuing too
many works in btrfs_wq_run_delayed_node and bail out of worker func if
at least BTRFS_DELAYED_WRITEBACK items are processed.

Changed in v2: remove support of thresh == NO_THRESHOLD.

Signed-off-by: Maxim Patlasov &lt;mpatlasov@virtuozzo.com&gt;
Signed-off-by: Chris Mason &lt;clm@fb.com&gt;
Cc: stable@vger.kernel.org # v3.15+
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