[PATCH 1/9] fs/locks: rename some lists and pointers.

From: NeilBrown
Date: Tue Oct 23 2018 - 18:45:46 EST

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struct file lock contains an 'fl_next' pointer which
is used to point to the lock that this request is blocked
waiting for. So rename it to fl_blocker.

The fl_blocked list_head in an active lock is the head of a list of
blocked requests. In a request it is a node in that list.
These are two distinct uses, so replace with two list_heads
with different names.
fl_blocked is the head of a list of blocked requests
fl_block is a node on that list.

The two different list_heads are never used at the same time, but that
will change in a future patch.

Note that a tracepoint is changed to report fl_blocker instead
of fl_next.

Signed-off-by: NeilBrown <neilb@xxxxxxxx>
---
fs/cifs/file.c | 2 +-
fs/locks.c | 38 ++++++++++++++++++++------------------
include/linux/fs.h | 7 +++++--
include/trace/events/filelock.h | 16 ++++++++--------
4 files changed, 34 insertions(+), 29 deletions(-)

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 8d41ca7bfcf1..066ed2e4ba96 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1092,7 +1092,7 @@ cifs_posix_lock_set(struct file *file, struct file_lock *flock)
rc = posix_lock_file(file, flock, NULL);
up_write(&cinode->lock_sem);
if (rc == FILE_LOCK_DEFERRED) {
- rc = wait_event_interruptible(flock->fl_wait, !flock->fl_next);
+ rc = wait_event_interruptible(flock->fl_wait, !flock->fl_blocker);
if (!rc)
goto try_again;
posix_unblock_lock(flock);
diff --git a/fs/locks.c b/fs/locks.c
index 2ecb4db8c840..a6c6d601286c 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -189,7 +189,7 @@ static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS);
* 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
+ * In addition, it also protects the fl->fl_blocked list, and the fl->fl_blocker
* pointer for file_lock structures that are acting as lock requests (in
* contrast to those that are acting as records of acquired locks).
*
@@ -293,6 +293,7 @@ static void locks_init_lock_heads(struct file_lock *fl)
{
INIT_HLIST_NODE(&fl->fl_link);
INIT_LIST_HEAD(&fl->fl_list);
+ INIT_LIST_HEAD(&fl->fl_blocked);
INIT_LIST_HEAD(&fl->fl_block);
init_waitqueue_head(&fl->fl_wait);
}
@@ -332,6 +333,7 @@ void locks_free_lock(struct file_lock *fl)
{
BUG_ON(waitqueue_active(&fl->fl_wait));
BUG_ON(!list_empty(&fl->fl_list));
+ BUG_ON(!list_empty(&fl->fl_blocked));
BUG_ON(!list_empty(&fl->fl_block));
BUG_ON(!hlist_unhashed(&fl->fl_link));

@@ -667,7 +669,7 @@ static void __locks_delete_block(struct file_lock *waiter)
{
locks_delete_global_blocked(waiter);
list_del_init(&waiter->fl_block);
- waiter->fl_next = NULL;
+ waiter->fl_blocker = NULL;
}

static void locks_delete_block(struct file_lock *waiter)
@@ -683,16 +685,16 @@ static void locks_delete_block(struct file_lock *waiter)
* it seems like the reasonable thing to do.
*
* Must be called with both the flc_lock and blocked_lock_lock held. The
- * fl_block list itself is protected by the blocked_lock_lock, but by ensuring
+ * fl_blocked list itself is protected by the blocked_lock_lock, but by ensuring
* that the flc_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.
+ * blocked_lock_lock in some cases when we see that the fl_blocked list is empty.
*/
static void __locks_insert_block(struct file_lock *blocker,
struct file_lock *waiter)
{
BUG_ON(!list_empty(&waiter->fl_block));
- waiter->fl_next = blocker;
- list_add_tail(&waiter->fl_block, &blocker->fl_block);
+ waiter->fl_blocker = blocker;
+ list_add_tail(&waiter->fl_block, &blocker->fl_blocked);
if (IS_POSIX(blocker) && !IS_OFDLCK(blocker))
locks_insert_global_blocked(waiter);
}
@@ -716,18 +718,18 @@ 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 flc_lock, and
- * the flc_lock is always held here. Note that removal from the fl_block
+ * the flc_lock is always held here. Note that removal from the fl_blocked
* list does not require the flc_lock, so we must recheck list_empty()
* after acquiring the blocked_lock_lock.
*/
- if (list_empty(&blocker->fl_block))
+ if (list_empty(&blocker->fl_blocked))
return;

spin_lock(&blocked_lock_lock);
- while (!list_empty(&blocker->fl_block)) {
+ while (!list_empty(&blocker->fl_blocked)) {
struct file_lock *waiter;

- waiter = list_first_entry(&blocker->fl_block,
+ waiter = list_first_entry(&blocker->fl_blocked,
struct file_lock, fl_block);
__locks_delete_block(waiter);
if (waiter->fl_lmops && waiter->fl_lmops->lm_notify)
@@ -878,7 +880,7 @@ static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)

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 fl->fl_blocker;
}
return NULL;
}
@@ -1237,7 +1239,7 @@ static int posix_lock_inode_wait(struct inode *inode, struct file_lock *fl)
error = posix_lock_inode(inode, fl, NULL);
if (error != FILE_LOCK_DEFERRED)
break;
- error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
+ error = wait_event_interruptible(fl->fl_wait, !fl->fl_blocker);
if (!error)
continue;

@@ -1324,7 +1326,7 @@ int locks_mandatory_area(struct inode *inode, struct file *filp, loff_t start,
error = posix_lock_inode(inode, &fl, NULL);
if (error != FILE_LOCK_DEFERRED)
break;
- error = wait_event_interruptible(fl.fl_wait, !fl.fl_next);
+ error = wait_event_interruptible(fl.fl_wait, !fl.fl_blocker);
if (!error) {
/*
* If we've been sleeping someone might have
@@ -1518,7 +1520,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)

locks_dispose_list(&dispose);
error = wait_event_interruptible_timeout(new_fl->fl_wait,
- !new_fl->fl_next, break_time);
+ !new_fl->fl_blocker, break_time);

percpu_down_read_preempt_disable(&file_rwsem);
spin_lock(&ctx->flc_lock);
@@ -1931,7 +1933,7 @@ static int flock_lock_inode_wait(struct inode *inode, struct file_lock *fl)
error = flock_lock_inode(inode, fl);
if (error != FILE_LOCK_DEFERRED)
break;
- error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
+ error = wait_event_interruptible(fl->fl_wait, !fl->fl_blocker);
if (!error)
continue;

@@ -2210,7 +2212,7 @@ static int do_lock_file_wait(struct file *filp, unsigned int cmd,
error = vfs_lock_file(filp, cmd, fl, NULL);
if (error != FILE_LOCK_DEFERRED)
break;
- error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
+ error = wait_event_interruptible(fl->fl_wait, !fl->fl_blocker);
if (!error)
continue;

@@ -2581,7 +2583,7 @@ posix_unblock_lock(struct file_lock *waiter)
int status = 0;

spin_lock(&blocked_lock_lock);
- if (waiter->fl_next)
+ if (waiter->fl_blocker)
__locks_delete_block(waiter);
else
status = -ENOENT;
@@ -2707,7 +2709,7 @@ static int locks_show(struct seq_file *f, void *v)

lock_get_status(f, fl, iter->li_pos, "");

- list_for_each_entry(bfl, &fl->fl_block, fl_block)
+ list_for_each_entry(bfl, &fl->fl_blocked, fl_block)
lock_get_status(f, bfl, iter->li_pos, " ->");

return 0;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 897eae8faee1..90c4331a0b2c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1025,10 +1025,13 @@ bool opens_in_grace(struct net *);
* Obviously, the last two criteria only matter for POSIX locks.
*/
struct file_lock {
- struct file_lock *fl_next; /* singly linked list for this inode */
+ struct file_lock *fl_blocker; /* The lock, that is blocking us */
struct list_head fl_list; /* link into file_lock_context */
struct hlist_node fl_link; /* node in global lists */
- struct list_head fl_block; /* circular list of blocked processes */
+ struct list_head fl_blocked; /* list of requests with
+ * ->fl_blocker pointing here */
+ struct list_head fl_block; /* node in
+ * ->fl_blocker->fl_blocked */
fl_owner_t fl_owner;
unsigned int fl_flags;
unsigned char fl_type;
diff --git a/include/trace/events/filelock.h b/include/trace/events/filelock.h
index 68b17c116907..fad7befa612d 100644
--- a/include/trace/events/filelock.h
+++ b/include/trace/events/filelock.h
@@ -68,7 +68,7 @@ DECLARE_EVENT_CLASS(filelock_lock,
__field(struct file_lock *, fl)
__field(unsigned long, i_ino)
__field(dev_t, s_dev)
- __field(struct file_lock *, fl_next)
+ __field(struct file_lock *, fl_blocker)
__field(fl_owner_t, fl_owner)
__field(unsigned int, fl_pid)
__field(unsigned int, fl_flags)
@@ -82,7 +82,7 @@ DECLARE_EVENT_CLASS(filelock_lock,
__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_blocker = fl ? fl->fl_blocker : 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;
@@ -92,9 +92,9 @@ DECLARE_EVENT_CLASS(filelock_lock,
__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",
+ TP_printk("fl=0x%p dev=0x%x:0x%x ino=0x%lx fl_blocker=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->i_ino, __entry->fl_blocker, __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)
@@ -125,7 +125,7 @@ DECLARE_EVENT_CLASS(filelock_lease,
__field(struct file_lock *, fl)
__field(unsigned long, i_ino)
__field(dev_t, s_dev)
- __field(struct file_lock *, fl_next)
+ __field(struct file_lock *, fl_blocker)
__field(fl_owner_t, fl_owner)
__field(unsigned int, fl_flags)
__field(unsigned char, fl_type)
@@ -137,7 +137,7 @@ DECLARE_EVENT_CLASS(filelock_lease,
__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_blocker = fl ? fl->fl_blocker : 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;
@@ -145,9 +145,9 @@ DECLARE_EVENT_CLASS(filelock_lease,
__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",
+ TP_printk("fl=0x%p dev=0x%x:0x%x ino=0x%lx fl_blocker=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,
+ __entry->i_ino, __entry->fl_blocker, __entry->fl_owner,
show_fl_flags(__entry->fl_flags),
show_fl_type(__entry->fl_type),
__entry->fl_break_time, __entry->fl_downgrade_time)

Next message: NeilBrown: "[PATCH 2/9] fs/locks: split out __locks_wake_up_blocks()."
Previous message: NeilBrown: "[PATCH 0/9 v3] locks: avoid thundering-herd wake-ups"
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