Re: [PATCH RFC 1/3] fs/lock: add new callback, lm_expire_lock, to lock_manager_operations

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On 2/3/22 10:41 AM, Chuck Lever III wrote:

On Jan 28, 2022, at 2:39 PM, Dai Ngo <dai.ngo@xxxxxxxxxx> wrote:

Add new callback, lm_expire_lock, to lock_manager_operations to allow
the lock manager to take appropriate action to resolve the lock conflict
if possible. The callback takes 1 argument, the file_lock of the blocker
and returns true if the conflict was resolved else returns false. Note
that the lock manager has to be able to resolve the conflict while
the spinlock flc_lock is held.

Lock manager, such as NFSv4 courteous server, uses this callback to
resolve conflict by destroying lock owner, or the NFSv4 courtesy client
(client that has expired but allowed to maintains its states) that owns
the lock.
This change is nice and simple now. The only issue is that the
short and long patch descriptions need to be updated to replace
"lm_expire_lock" with "lm_lock_conflict".

Fix in v11.

Thanks,
-Dai



Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
---
Documentation/filesystems/locking.rst |  2 ++
fs/locks.c                            | 14 ++++++++++----
include/linux/fs.h                    |  1 +
3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
index d36fe79167b3..57ce0fbc8ab1 100644
--- a/Documentation/filesystems/locking.rst
+++ b/Documentation/filesystems/locking.rst
@@ -439,6 +439,7 @@ prototypes::
	void (*lm_break)(struct file_lock *); /* break_lease callback */
	int (*lm_change)(struct file_lock **, int);
	bool (*lm_breaker_owns_lease)(struct file_lock *);
+	bool (*lm_lock_conflict)(struct file_lock *);

locking rules:

@@ -450,6 +451,7 @@ lm_grant:		no		no			no
lm_break:		yes		no			no
lm_change		yes		no			no
lm_breaker_owns_lease:	no		no			no
+lm_lock_conflict:       no		no			no
======================	=============	=================	=========

buffer_head
diff --git a/fs/locks.c b/fs/locks.c
index 0fca9d680978..052b42cc7f25 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -853,10 +853,13 @@ posix_test_lock(struct file *filp, struct file_lock *fl)

	spin_lock(&ctx->flc_lock);
	list_for_each_entry(cfl, &ctx->flc_posix, fl_list) {
-		if (posix_locks_conflict(fl, cfl)) {
-			locks_copy_conflock(fl, cfl);
-			goto out;
-		}
+		if (!posix_locks_conflict(fl, cfl))
+			continue;
+		if (cfl->fl_lmops && cfl->fl_lmops->lm_lock_conflict &&
+			!cfl->fl_lmops->lm_lock_conflict(cfl))
+			continue;
+		locks_copy_conflock(fl, cfl);
+		goto out;
	}
	fl->fl_type = F_UNLCK;
out:
@@ -1059,6 +1062,9 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request,
		list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
			if (!posix_locks_conflict(request, fl))
				continue;
+			if (fl->fl_lmops && fl->fl_lmops->lm_lock_conflict &&
+				!fl->fl_lmops->lm_lock_conflict(fl))
+				continue;
			if (conflock)
				locks_copy_conflock(conflock, fl);
			error = -EAGAIN;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index bbf812ce89a8..21cb7afe2d63 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1068,6 +1068,7 @@ struct lock_manager_operations {
	int (*lm_change)(struct file_lock *, int, struct list_head *);
	void (*lm_setup)(struct file_lock *, void **);
	bool (*lm_breaker_owns_lease)(struct file_lock *);
+	bool (*lm_lock_conflict)(struct file_lock *cfl);
};

struct lock_manager {
--
2.9.5

--
Chuck Lever






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