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

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 2/3/22 2:50 PM, Jeff Layton wrote:
On Fri, 2022-01-28 at 11:39 -0800, Dai Ngo 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.

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;
The naming of this op is a little misleading. We already know that there
is a lock confict in this case. The question is whether it's resolvable
by expiring a tardy client. That said, I don't have a better name to
suggest at the moment.

I will leave it as is for now.


A comment about what this function actually tells us would be nice here.

will do in v11.

Thanks,
-Dai


  			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 {
Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>




[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [NTFS 3]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [NTFS 3]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux