diff mbox series

[v2,4/5] xfs: Remove mrlock wrapper

Message ID 20231007203543.1377452-5-willy@infradead.org (mailing list archive)
State New
Headers show
Series Remove the XFS mrlock | expand

Commit Message

Matthew Wilcox Oct. 7, 2023, 8:35 p.m. UTC
mrlock was an rwsem wrapper that also recorded whether the lock was
held for read or write.  Now that we can ask the generic code whether
the lock is held for read or write, we can remove this wrapper and use
an rwsem directly.

As the comment says, we can't use lockdep to assert that the ILOCK is
held for write, because we might be in a workqueue, and we aren't able
to tell lockdep that we do in fact own the lock.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/xfs/mrlock.h    | 78 ----------------------------------------------
 fs/xfs/xfs_inode.c | 22 +++++++------
 fs/xfs/xfs_inode.h |  2 +-
 fs/xfs/xfs_iops.c  |  4 +--
 fs/xfs/xfs_linux.h |  2 +-
 fs/xfs/xfs_super.c |  4 +--
 6 files changed, 18 insertions(+), 94 deletions(-)
 delete mode 100644 fs/xfs/mrlock.h

Comments

Dave Chinner Oct. 8, 2023, 10:17 p.m. UTC | #1
On Sat, Oct 07, 2023 at 09:35:42PM +0100, Matthew Wilcox (Oracle) wrote:
> mrlock was an rwsem wrapper that also recorded whether the lock was
> held for read or write.  Now that we can ask the generic code whether
> the lock is held for read or write, we can remove this wrapper and use
> an rwsem directly.
> 
> As the comment says, we can't use lockdep to assert that the ILOCK is
> held for write, because we might be in a workqueue, and we aren't able
> to tell lockdep that we do in fact own the lock.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

.....

> @@ -338,10 +338,14 @@ xfs_assert_ilocked(
>  	struct xfs_inode	*ip,
>  	uint			lock_flags)
>  {
> +	/*
> +	 * Sometimes we assert the ILOCK is held exclusively, but we're in
> +	 * a workqueue, so lockdep doesn't know we're the owner.
> +	 */
>  	if (lock_flags & XFS_ILOCK_SHARED)
> -		rwsem_assert_held(&ip->i_lock.mr_lock);
> +		rwsem_assert_held(&ip->i_lock);
>  	else if (lock_flags & XFS_ILOCK_EXCL)
> -		BUG_ON(!ip->i_lock.mr_writer);
> +		__rwsem_assert_held_write(&ip->i_lock);

It took me ages to work out that the comment related to the "__"
variant of rwsem_assert_held_write() function. I really dislike the
use of "__" prefixes for a function with slightly different,
non-obvious semantics to the parent - it's way too subtle for it to
be clear that this is what the comment is refering to.

In this case, we effectively have rwsem_assert_held_write() that
does lockdep checks, and __rwsem_assert_held_write() that does not
do lockdep checks. Either the former needs to say "lockdep" or the
latter needs "nolockdep" in the name to indicate to the reader the
intent of the code calling the checking function....

Otherwise the code looks fine.

-Dave.
diff mbox series

Patch

diff --git a/fs/xfs/mrlock.h b/fs/xfs/mrlock.h
deleted file mode 100644
index 79155eec341b..000000000000
--- a/fs/xfs/mrlock.h
+++ /dev/null
@@ -1,78 +0,0 @@ 
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (c) 2000-2006 Silicon Graphics, Inc.
- * All Rights Reserved.
- */
-#ifndef __XFS_SUPPORT_MRLOCK_H__
-#define __XFS_SUPPORT_MRLOCK_H__
-
-#include <linux/rwsem.h>
-
-typedef struct {
-	struct rw_semaphore	mr_lock;
-#if defined(DEBUG) || defined(XFS_WARN)
-	int			mr_writer;
-#endif
-} mrlock_t;
-
-#if defined(DEBUG) || defined(XFS_WARN)
-#define mrinit(mrp, name)	\
-	do { (mrp)->mr_writer = 0; init_rwsem(&(mrp)->mr_lock); } while (0)
-#else
-#define mrinit(mrp, name)	\
-	do { init_rwsem(&(mrp)->mr_lock); } while (0)
-#endif
-
-#define mrlock_init(mrp, t,n,s)	mrinit(mrp, n)
-#define mrfree(mrp)		do { } while (0)
-
-static inline void mraccess_nested(mrlock_t *mrp, int subclass)
-{
-	down_read_nested(&mrp->mr_lock, subclass);
-}
-
-static inline void mrupdate_nested(mrlock_t *mrp, int subclass)
-{
-	down_write_nested(&mrp->mr_lock, subclass);
-#if defined(DEBUG) || defined(XFS_WARN)
-	mrp->mr_writer = 1;
-#endif
-}
-
-static inline int mrtryaccess(mrlock_t *mrp)
-{
-	return down_read_trylock(&mrp->mr_lock);
-}
-
-static inline int mrtryupdate(mrlock_t *mrp)
-{
-	if (!down_write_trylock(&mrp->mr_lock))
-		return 0;
-#if defined(DEBUG) || defined(XFS_WARN)
-	mrp->mr_writer = 1;
-#endif
-	return 1;
-}
-
-static inline void mrunlock_excl(mrlock_t *mrp)
-{
-#if defined(DEBUG) || defined(XFS_WARN)
-	mrp->mr_writer = 0;
-#endif
-	up_write(&mrp->mr_lock);
-}
-
-static inline void mrunlock_shared(mrlock_t *mrp)
-{
-	up_read(&mrp->mr_lock);
-}
-
-static inline void mrdemote(mrlock_t *mrp)
-{
-#if defined(DEBUG) || defined(XFS_WARN)
-	mrp->mr_writer = 0;
-#endif
-	downgrade_write(&mrp->mr_lock);
-}
-
-#endif /* __XFS_SUPPORT_MRLOCK_H__ */
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 812d6f255d84..a6d9a834d869 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -208,9 +208,9 @@  xfs_ilock(
 	}
 
 	if (lock_flags & XFS_ILOCK_EXCL)
-		mrupdate_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
+		down_write_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
 	else if (lock_flags & XFS_ILOCK_SHARED)
-		mraccess_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
+		down_read_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
 }
 
 /*
@@ -251,10 +251,10 @@  xfs_ilock_nowait(
 	}
 
 	if (lock_flags & XFS_ILOCK_EXCL) {
-		if (!mrtryupdate(&ip->i_lock))
+		if (!down_write_trylock(&ip->i_lock))
 			goto out_undo_mmaplock;
 	} else if (lock_flags & XFS_ILOCK_SHARED) {
-		if (!mrtryaccess(&ip->i_lock))
+		if (!down_read_trylock(&ip->i_lock))
 			goto out_undo_mmaplock;
 	}
 	return 1;
@@ -303,9 +303,9 @@  xfs_iunlock(
 		up_read(&VFS_I(ip)->i_mapping->invalidate_lock);
 
 	if (lock_flags & XFS_ILOCK_EXCL)
-		mrunlock_excl(&ip->i_lock);
+		up_write(&ip->i_lock);
 	else if (lock_flags & XFS_ILOCK_SHARED)
-		mrunlock_shared(&ip->i_lock);
+		up_read(&ip->i_lock);
 
 	trace_xfs_iunlock(ip, lock_flags, _RET_IP_);
 }
@@ -324,7 +324,7 @@  xfs_ilock_demote(
 		~(XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL|XFS_ILOCK_EXCL)) == 0);
 
 	if (lock_flags & XFS_ILOCK_EXCL)
-		mrdemote(&ip->i_lock);
+		downgrade_write(&ip->i_lock);
 	if (lock_flags & XFS_MMAPLOCK_EXCL)
 		downgrade_write(&VFS_I(ip)->i_mapping->invalidate_lock);
 	if (lock_flags & XFS_IOLOCK_EXCL)
@@ -338,10 +338,14 @@  xfs_assert_ilocked(
 	struct xfs_inode	*ip,
 	uint			lock_flags)
 {
+	/*
+	 * Sometimes we assert the ILOCK is held exclusively, but we're in
+	 * a workqueue, so lockdep doesn't know we're the owner.
+	 */
 	if (lock_flags & XFS_ILOCK_SHARED)
-		rwsem_assert_held(&ip->i_lock.mr_lock);
+		rwsem_assert_held(&ip->i_lock);
 	else if (lock_flags & XFS_ILOCK_EXCL)
-		BUG_ON(!ip->i_lock.mr_writer);
+		__rwsem_assert_held_write(&ip->i_lock);
 
 	if (lock_flags & XFS_MMAPLOCK_SHARED)
 		rwsem_assert_held(&VFS_I(ip)->i_mapping->invalidate_lock);
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index b70f3e8e4525..1c2484b6afff 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -39,7 +39,7 @@  typedef struct xfs_inode {
 
 	/* Transaction and locking information. */
 	struct xfs_inode_log_item *i_itemp;	/* logging information */
-	mrlock_t		i_lock;		/* inode lock */
+	struct rw_semaphore	i_lock;		/* inode lock */
 	atomic_t		i_pincount;	/* inode pin count */
 	struct llist_node	i_gclist;	/* deferred inactivation list */
 
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 2492b746912e..fcceb2b4e40d 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1279,9 +1279,9 @@  xfs_setup_inode(
 		 */
 		lockdep_set_class(&inode->i_rwsem,
 				  &inode->i_sb->s_type->i_mutex_dir_key);
-		lockdep_set_class(&ip->i_lock.mr_lock, &xfs_dir_ilock_class);
+		lockdep_set_class(&ip->i_lock, &xfs_dir_ilock_class);
 	} else {
-		lockdep_set_class(&ip->i_lock.mr_lock, &xfs_nondir_ilock_class);
+		lockdep_set_class(&ip->i_lock, &xfs_nondir_ilock_class);
 	}
 
 	/*
diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index e9d317a3dafe..15fdaef578fe 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -22,7 +22,6 @@  typedef __u32			xfs_nlink_t;
 #include "xfs_types.h"
 
 #include "kmem.h"
-#include "mrlock.h"
 
 #include <linux/semaphore.h>
 #include <linux/mm.h>
@@ -51,6 +50,7 @@  typedef __u32			xfs_nlink_t;
 #include <linux/notifier.h>
 #include <linux/delay.h>
 #include <linux/log2.h>
+#include <linux/rwsem.h>
 #include <linux/spinlock.h>
 #include <linux/random.h>
 #include <linux/ctype.h>
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 819a3568b28f..19435fa4c6b3 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -717,9 +717,7 @@  xfs_fs_inode_init_once(
 	/* xfs inode */
 	atomic_set(&ip->i_pincount, 0);
 	spin_lock_init(&ip->i_flags_lock);
-
-	mrlock_init(&ip->i_lock, MRLOCK_ALLOW_EQUAL_PRI|MRLOCK_BARRIER,
-		     "xfsino", ip->i_ino);
+	init_rwsem(&ip->i_lock);
 }
 
 /*