Message-Id: <201009151830.43470.arnd@arndb.de>
Date:	Wed, 15 Sep 2010 18:30:43 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Matthew Wilcox <willy@...ux.intel.com>,
	Christoph Hellwig <hch@....de>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Miklos Szeredi <mszeredi@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, John Kacur <jkacur@...hat.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] Remove BKL from fs/locks.c

On Tuesday 14 September 2010, Trond Myklebust wrote:
> Would it be possible to at least merge a patch that defines
> lock_flocks() (even if it just is an alias for lock_kernel()), so that
> we can convert those bits of the lock recovery code that need to peek
> into the inode->i_flock list ASAP?

Fine with me.

Another alternative would be to keep a series of all these patches
together, like

1. fs/locks.c: prepare for BKL removal
2. fs/lockd: use lock/flocks
3. fs/locks.c: lock_flocks using spinlock (trivial)

Feel free to take the patch below into a tree of yours when
adding patches 2 and 3 on top, or send me that patch once
it's done and I'll add both into my tree.

Linus, Christoph: Does the patch below look ok? I've removed
the CONFIG_BKL stuff in it now and changed over everything
besides lockd to use lock_flocks(). I'd like to put this into
the -next queue (after some basic testing).
---
Subject: [PATCH] fs/locks.c: prepare for BKL removal

This prepares the removal of the big kernel lock from the
file locking code. We still use the BKL as long as fs/lockd
uses it, but flip the definition to a private spinlock
as soon as that's done.

All users outside of fs/lockd get converted to use
lock_flocks() instead of lock_kernel() where appropriate.

Based on an earlier patch from Matthew Wilcox.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Cc: Matthew Wilcox <willy@...ux.intel.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Trond Myklebust <trond.myklebust@....uio.no>
Cc: "J. Bruce Fields" <bfields@...ldses.org>
Cc: Miklos Szeredi <mszeredi@...e.cz>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: John Kacur <jkacur@...hat.com>
Cc: linux-kernel@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org
---

 fs/afs/flock.c       |    5 +-
 fs/ceph/mds_client.c |    6 +-
 fs/locks.c           |  118 ++++++++++++++++++++++++++++---------------------
 fs/nfs/delegation.c  |   10 ++--
 fs/nfs/nfs4state.c   |   10 ++--
 fs/nfsd/nfs4state.c  |    6 +-
 include/linux/fs.h   |   10 ++++
 7 files changed, 95 insertions(+), 70 deletions(-)

diff --git a/fs/afs/flock.c b/fs/afs/flock.c
index 0931bc1..757d664 100644
--- a/fs/afs/flock.c
+++ b/fs/afs/flock.c
@@ -9,7 +9,6 @@
  * 2 of the License, or (at your option) any later version.
  */
 
-#include <linux/smp_lock.h>
 #include "internal.h"
 
 #define AFS_LOCK_GRANTED	0
@@ -274,7 +273,7 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl)
 
 	type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
 
-	lock_kernel();
+	lock_flocks();
 
 	/* make sure we've got a callback on this file and that our view of the
 	 * data version is up to date */
@@ -421,7 +420,7 @@ given_lock:
 	afs_vnode_fetch_status(vnode, NULL, key);
 
 error:
-	unlock_kernel();
+	unlock_flocks();
 	_leave(" = %d", ret);
 	return ret;
 
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index f091b13..bda5211 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -3,7 +3,7 @@
 #include <linux/wait.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
-#include <linux/smp_lock.h>
+#include <linux/fs.h>
 
 #include "mds_client.h"
 #include "mon_client.h"
@@ -2362,7 +2362,7 @@ static int encode_caps_cb(struct inode *inode, struct ceph_cap *cap,
 	if (recon_state->flock) {
 		int num_fcntl_locks, num_flock_locks;
 
-		lock_kernel();
+		lock_flocks();
 		ceph_count_locks(inode, &num_fcntl_locks, &num_flock_locks);
 		rec.v2.flock_len = (2*sizeof(u32) +
 				    (num_fcntl_locks+num_flock_locks) *
@@ -2373,7 +2373,7 @@ static int encode_caps_cb(struct inode *inode, struct ceph_cap *cap,
 			err = ceph_encode_locks(inode, pagelist,
 						num_fcntl_locks,
 						num_flock_locks);
-		unlock_kernel();
+		unlock_flocks();
 	}
 
 out_free:
diff --git a/fs/locks.c b/fs/locks.c
index ab24d49..8c6935f 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -143,6 +143,21 @@ int lease_break_time = 45;
 static LIST_HEAD(file_lock_list);
 static LIST_HEAD(blocked_list);
 
+/*
+ * Protects the two list heads above, plus the inode->i_flock list
+ * FIXME: should use a spinlock, once fs/lockd uses lock_flocks().
+ */
+void lock_flocks(void)
+{
+	lock_kernel();
+}
+EXPORT_SYMBOL(lock_flocks);
+
+void unlock_flocks(void)
+{
+	unlock_kernel();
+}
+
 static struct kmem_cache *filelock_cache __read_mostly;
 
 /* Allocate an empty lock structure. */
@@ -511,9 +526,9 @@ static void __locks_delete_block(struct file_lock *waiter)
  */
 static void locks_delete_block(struct file_lock *waiter)
 {
-	lock_kernel();
+	lock_flocks();
 	__locks_delete_block(waiter);
-	unlock_kernel();
+	unlock_flocks();
 }
 
 /* Insert waiter into blocker's block list.
@@ -644,7 +659,7 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
 {
 	struct file_lock *cfl;
 
-	lock_kernel();
+	lock_flocks();
 	for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
 		if (!IS_POSIX(cfl))
 			continue;
@@ -657,7 +672,7 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
 			fl->fl_pid = pid_vnr(cfl->fl_nspid);
 	} else
 		fl->fl_type = F_UNLCK;
-	unlock_kernel();
+	unlock_flocks();
 	return;
 }
 EXPORT_SYMBOL(posix_test_lock);
@@ -730,18 +745,16 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
 	int error = 0;
 	int found = 0;
 
-	lock_kernel();
-	if (request->fl_flags & FL_ACCESS)
-		goto find_conflict;
-
-	if (request->fl_type != F_UNLCK) {
-		error = -ENOMEM;
+	if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
 		new_fl = locks_alloc_lock();
-		if (new_fl == NULL)
-			goto out;
-		error = 0;
+		if (!new_fl)
+			return -ENOMEM;
 	}
 
+	lock_flocks();
+	if (request->fl_flags & FL_ACCESS)
+		goto find_conflict;
+
 	for_each_lock(inode, before) {
 		struct file_lock *fl = *before;
 		if (IS_POSIX(fl))
@@ -767,8 +780,11 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
 	 * If a higher-priority process was blocked on the old file lock,
 	 * give it the opportunity to lock the file.
 	 */
-	if (found)
+	if (found) {
+		unlock_flocks();
 		cond_resched();
+		lock_flocks();
+	}
 
 find_conflict:
 	for_each_lock(inode, before) {
@@ -794,7 +810,7 @@ find_conflict:
 	error = 0;
 
 out:
-	unlock_kernel();
+	unlock_flocks();
 	if (new_fl)
 		locks_free_lock(new_fl);
 	return error;
@@ -823,7 +839,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
 		new_fl2 = locks_alloc_lock();
 	}
 
-	lock_kernel();
+	lock_flocks();
 	if (request->fl_type != F_UNLCK) {
 		for_each_lock(inode, before) {
 			fl = *before;
@@ -991,7 +1007,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
 		locks_wake_up_blocks(left);
 	}
  out:
-	unlock_kernel();
+	unlock_flocks();
 	/*
 	 * Free any unused locks.
 	 */
@@ -1066,14 +1082,14 @@ int locks_mandatory_locked(struct inode *inode)
 	/*
 	 * Search the lock list for this inode for any POSIX locks.
 	 */
-	lock_kernel();
+	lock_flocks();
 	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
 		if (!IS_POSIX(fl))
 			continue;
 		if (fl->fl_owner != owner)
 			break;
 	}
-	unlock_kernel();
+	unlock_flocks();
 	return fl ? -EAGAIN : 0;
 }
 
@@ -1186,7 +1202,7 @@ int __break_lease(struct inode *inode, unsigned int mode)
 
 	new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
 
-	lock_kernel();
+	lock_flocks();
 
 	time_out_leases(inode);
 
@@ -1247,8 +1263,10 @@ restart:
 			break_time++;
 	}
 	locks_insert_block(flock, new_fl);
+	unlock_flocks();
 	error = wait_event_interruptible_timeout(new_fl->fl_wait,
 						!new_fl->fl_next, break_time);
+	lock_flocks();
 	__locks_delete_block(new_fl);
 	if (error >= 0) {
 		if (error == 0)
@@ -1263,7 +1281,7 @@ restart:
 	}
 
 out:
-	unlock_kernel();
+	unlock_flocks();
 	if (!IS_ERR(new_fl))
 		locks_free_lock(new_fl);
 	return error;
@@ -1319,7 +1337,7 @@ int fcntl_getlease(struct file *filp)
 	struct file_lock *fl;
 	int type = F_UNLCK;
 
-	lock_kernel();
+	lock_flocks();
 	time_out_leases(filp->f_path.dentry->d_inode);
 	for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl);
 			fl = fl->fl_next) {
@@ -1328,7 +1346,7 @@ int fcntl_getlease(struct file *filp)
 			break;
 		}
 	}
-	unlock_kernel();
+	unlock_flocks();
 	return type;
 }
 
@@ -1341,7 +1359,7 @@ int fcntl_getlease(struct file *filp)
  *	The (input) flp->fl_lmops->fl_break function is required
  *	by break_lease().
  *
- *	Called with kernel lock held.
+ *	Called with file_lock_lock held.
  */
 int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
 {
@@ -1359,6 +1377,13 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
 	if (error)
 		return error;
 
+	if (arg != F_UNLCK) {
+		new_fl = locks_alloc_lock();
+		if (new_fl == NULL)
+			return -ENOMEM;
+	}
+
+	lock_flocks();
 	time_out_leases(inode);
 
 	BUG_ON(!(*flp)->fl_lmops->fl_break);
@@ -1366,11 +1391,6 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
 	lease = *flp;
 
 	if (arg != F_UNLCK) {
-		error = -ENOMEM;
-		new_fl = locks_alloc_lock();
-		if (new_fl == NULL)
-			goto out;
-
 		error = -EAGAIN;
 		if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
 			goto out;
@@ -1427,16 +1447,18 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
 	locks_insert_lock(before, new_fl);
 
 	*flp = new_fl;
+	unlock_flocks();
 	return 0;
 
 out:
 	if (new_fl != NULL)
 		locks_free_lock(new_fl);
+	unlock_flocks();
 	return error;
 }
 EXPORT_SYMBOL(generic_setlease);
 
- /**
+/**
  *	vfs_setlease        -       sets a lease on an open file
  *	@filp: file pointer
  *	@arg: type of lease to obtain
@@ -1465,16 +1487,10 @@ EXPORT_SYMBOL(generic_setlease);
 
 int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
 {
-	int error;
-
-	lock_kernel();
 	if (filp->f_op && filp->f_op->setlease)
-		error = filp->f_op->setlease(filp, arg, lease);
+		return filp->f_op->setlease(filp, arg, lease);
 	else
-		error = generic_setlease(filp, arg, lease);
-	unlock_kernel();
-
-	return error;
+		return generic_setlease(filp, arg, lease);
 }
 EXPORT_SYMBOL_GPL(vfs_setlease);
 
@@ -1499,12 +1515,12 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
 	if (error)
 		return error;
 
-	lock_kernel();
-
 	error = vfs_setlease(filp, arg, &flp);
 	if (error || arg == F_UNLCK)
 		goto out_unlock;
 
+	lock_flocks();
+
 	error = fasync_helper(fd, filp, 1, &flp->fl_fasync);
 	if (error < 0) {
 		/* remove lease just inserted by setlease */
@@ -1516,7 +1532,7 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
 
 	error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
 out_unlock:
-	unlock_kernel();
+	unlock_flocks();
 	return error;
 }
 
@@ -2020,7 +2036,7 @@ void locks_remove_flock(struct file *filp)
 			fl.fl_ops->fl_release_private(&fl);
 	}
 
-	lock_kernel();
+	lock_flocks();
 	before = &inode->i_flock;
 
 	while ((fl = *before) != NULL) {
@@ -2038,7 +2054,7 @@ void locks_remove_flock(struct file *filp)
  		}
 		before = &fl->fl_next;
 	}
-	unlock_kernel();
+	unlock_flocks();
 }
 
 /**
@@ -2053,12 +2069,12 @@ posix_unblock_lock(struct file *filp, struct file_lock *waiter)
 {
 	int status = 0;
 
-	lock_kernel();
+	lock_flocks();
 	if (waiter->fl_next)
 		__locks_delete_block(waiter);
 	else
 		status = -ENOENT;
-	unlock_kernel();
+	unlock_flocks();
 	return status;
 }
 
@@ -2172,7 +2188,7 @@ static int locks_show(struct seq_file *f, void *v)
 
 static void *locks_start(struct seq_file *f, loff_t *pos)
 {
-	lock_kernel();
+	lock_flocks();
 	f->private = (void *)1;
 	return seq_list_start(&file_lock_list, *pos);
 }
@@ -2184,7 +2200,7 @@ static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
 
 static void locks_stop(struct seq_file *f, void *v)
 {
-	unlock_kernel();
+	unlock_flocks();
 }
 
 static const struct seq_operations locks_seq_operations = {
@@ -2231,7 +2247,7 @@ int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
 {
 	struct file_lock *fl;
 	int result = 1;
-	lock_kernel();
+	lock_flocks();
 	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
 		if (IS_POSIX(fl)) {
 			if (fl->fl_type == F_RDLCK)
@@ -2248,7 +2264,7 @@ int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
 		result = 0;
 		break;
 	}
-	unlock_kernel();
+	unlock_flocks();
 	return result;
 }
 
@@ -2271,7 +2287,7 @@ int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
 {
 	struct file_lock *fl;
 	int result = 1;
-	lock_kernel();
+	lock_flocks();
 	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
 		if (IS_POSIX(fl)) {
 			if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
@@ -2286,7 +2302,7 @@ int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
 		result = 0;
 		break;
 	}
-	unlock_kernel();
+	unlock_flocks();
 	return result;
 }
 
diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index b9c3c43..232a7ee 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -71,20 +71,20 @@ static int nfs_delegation_claim_locks(struct nfs_open_context *ctx, struct nfs4_
 	if (inode->i_flock == NULL)
 		goto out;
 
-	/* Protect inode->i_flock using the BKL */
-	lock_kernel();
+	/* Protect inode->i_flock using the file locks lock */
+	lock_flocks();
 	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
 		if (!(fl->fl_flags & (FL_POSIX|FL_FLOCK)))
 			continue;
 		if (nfs_file_open_context(fl->fl_file) != ctx)
 			continue;
-		unlock_kernel();
+		unlock_flocks();
 		status = nfs4_lock_delegation_recall(state, fl);
 		if (status < 0)
 			goto out;
-		lock_kernel();
+		lock_flocks();
 	}
-	unlock_kernel();
+	unlock_flocks();
 out:
 	return status;
 }
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 3e2f19b..96524c5 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -40,7 +40,7 @@
 
 #include <linux/kernel.h>
 #include <linux/slab.h>
-#include <linux/smp_lock.h>
+#include <linux/fs.h>
 #include <linux/nfs_fs.h>
 #include <linux/nfs_idmap.h>
 #include <linux/kthread.h>
@@ -970,13 +970,13 @@ static int nfs4_reclaim_locks(struct nfs4_state *state, const struct nfs4_state_
 	/* Guard against delegation returns and new lock/unlock calls */
 	down_write(&nfsi->rwsem);
 	/* Protect inode->i_flock using the BKL */
-	lock_kernel();
+	lock_flocks();
 	for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
 		if (!(fl->fl_flags & (FL_POSIX|FL_FLOCK)))
 			continue;
 		if (nfs_file_open_context(fl->fl_file)->state != state)
 			continue;
-		unlock_kernel();
+		unlock_flocks();
 		status = ops->recover_lock(state, fl);
 		switch (status) {
 			case 0:
@@ -1003,9 +1003,9 @@ static int nfs4_reclaim_locks(struct nfs4_state *state, const struct nfs4_state_
 				/* kill_proc(fl->fl_pid, SIGLOST, 1); */
 				status = 0;
 		}
-		lock_kernel();
+		lock_flocks();
 	}
-	unlock_kernel();
+	unlock_flocks();
 out:
 	up_write(&nfsi->rwsem);
 	return status;
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index cf0d2ff..a7292fc 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -33,7 +33,7 @@
 */
 
 #include <linux/file.h>
-#include <linux/smp_lock.h>
+#include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/namei.h>
 #include <linux/swap.h>
@@ -3895,7 +3895,7 @@ check_for_locks(struct nfs4_file *filp, struct nfs4_stateowner *lowner)
 	struct inode *inode = filp->fi_inode;
 	int status = 0;
 
-	lock_kernel();
+	lock_flocks();
 	for (flpp = &inode->i_flock; *flpp != NULL; flpp = &(*flpp)->fl_next) {
 		if ((*flpp)->fl_owner == (fl_owner_t)lowner) {
 			status = 1;
@@ -3903,7 +3903,7 @@ check_for_locks(struct nfs4_file *filp, struct nfs4_stateowner *lowner)
 		}
 	}
 out:
-	unlock_kernel();
+	unlock_flocks();
 	return status;
 }
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0ec4d60..fd85cd2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1127,6 +1127,8 @@ extern int vfs_setlease(struct file *, long, struct file_lock **);
 extern int lease_modify(struct file_lock **, int);
 extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
 extern int lock_may_write(struct inode *, loff_t start, unsigned long count);
+extern void lock_flocks(void);
+extern void unlock_flocks(void);
 #else /* !CONFIG_FILE_LOCKING */
 static inline int fcntl_getlk(struct file *file, struct flock __user *user)
 {
@@ -1269,6 +1271,14 @@ static inline int lock_may_write(struct inode *inode, loff_t start,
 	return 1;
 }
 
+static inline void lock_flocks()
+{
+}
+
+static inline void unlock_flocks()
+{
+}
+
 #endif /* !CONFIG_FILE_LOCKING */
 
 
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