Merge branch 'xfs-mmap-lock' into for-next

fs/xfs/xfs_bmap_util.c

@@ -1599,13 +1599,6 @@ xfs_swap_extent_flush(
 	/* Verify O_DIRECT for ftmp */
 	if (VFS_I(ip)->i_mapping->nrpages)
 		return -EINVAL;
-
-	/*
-	 * Don't try to swap extents on mmap()d files because we can't lock
-	 * out races against page faults safely.
-	 */
-	if (mapping_mapped(VFS_I(ip)->i_mapping))
-		return -EBUSY;
 	return 0;
 }
 
@@ -1633,13 +1626,14 @@ xfs_swap_extents(
 	}
 
 	/*
-	 * Lock up the inodes against other IO and truncate to begin with.
-	 * Then we can ensure the inodes are flushed and have no page cache
-	 * safely. Once we have done this we can take the ilocks and do the rest
-	 * of the checks.
+	 * Lock the inodes against other IO, page faults and truncate to
+	 * begin with.  Then we can ensure the inodes are flushed and have no
+	 * page cache safely. Once we have done this we can take the ilocks and
+	 * do the rest of the checks.
 	 */
-	lock_flags = XFS_IOLOCK_EXCL;
+	lock_flags = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
 	xfs_lock_two_inodes(ip, tip, XFS_IOLOCK_EXCL);
+	xfs_lock_two_inodes(ip, tip, XFS_MMAPLOCK_EXCL);
 
 	/* Verify that both files have the same format */
 	if ((ip->i_d.di_mode & S_IFMT) != (tip->i_d.di_mode & S_IFMT)) {
@@ -1666,8 +1660,16 @@ xfs_swap_extents(
 		xfs_trans_cancel(tp, 0);
 		goto out_unlock;
 	}
+
+	/*
+	 * Lock and join the inodes to the tansaction so that transaction commit
+	 * or cancel will unlock the inodes from this point onwards.
+	 */
 	xfs_lock_two_inodes(ip, tip, XFS_ILOCK_EXCL);
 	lock_flags |= XFS_ILOCK_EXCL;
+	xfs_trans_ijoin(tp, ip, lock_flags);
+	xfs_trans_ijoin(tp, tip, lock_flags);
+
 
 	/* Verify all data are being swapped */
 	if (sxp->sx_offset != 0 ||
@@ -1720,9 +1722,6 @@ xfs_swap_extents(
 			goto out_trans_cancel;
 	}
 
-	xfs_trans_ijoin(tp, ip, lock_flags);
-	xfs_trans_ijoin(tp, tip, lock_flags);
-
 	/*
 	 * Before we've swapped the forks, lets set the owners of the forks
 	 * appropriately. We have to do this as we are demand paging the btree
@@ -1856,5 +1855,5 @@ xfs_swap_extents(
 
 out_trans_cancel:
 	xfs_trans_cancel(tp, 0);
-	goto out_unlock;
+	goto out;
 }

fs/xfs/xfs_file.c

@@ -847,6 +847,9 @@ xfs_file_fallocate(
 	if (error)
 		goto out_unlock;
 
+	xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
+	iolock |= XFS_MMAPLOCK_EXCL;
+
 	if (mode & FALLOC_FL_PUNCH_HOLE) {
 		error = xfs_free_file_space(ip, offset, len);
 		if (error)
@@ -996,20 +999,6 @@ xfs_file_mmap(
 	return 0;
 }
 
-/*
- * mmap()d file has taken write protection fault and is being made
- * writable. We can set the page state up correctly for a writable
- * page, which means we can do correct delalloc accounting (ENOSPC
- * checking!) and unwritten extent mapping.
- */
-STATIC int
-xfs_vm_page_mkwrite(
-	struct vm_area_struct	*vma,
-	struct vm_fault		*vmf)
-{
-	return block_page_mkwrite(vma, vmf, xfs_get_blocks);
-}
-
 /*
  * This type is designed to indicate the type of offset we would like
  * to search from page cache for xfs_seek_hole_data().
@@ -1385,6 +1374,55 @@ xfs_file_llseek(
 	}
 }
 
+/*
+ * Locking for serialisation of IO during page faults. This results in a lock
+ * ordering of:
+ *
+ * mmap_sem (MM)
+ *   i_mmap_lock (XFS - truncate serialisation)
+ *     page_lock (MM)
+ *       i_lock (XFS - extent map serialisation)
+ */
+STATIC int
+xfs_filemap_fault(
+	struct vm_area_struct	*vma,
+	struct vm_fault		*vmf)
+{
+	struct xfs_inode	*ip = XFS_I(vma->vm_file->f_mapping->host);
+	int			error;
+
+	trace_xfs_filemap_fault(ip);
+
+	xfs_ilock(ip, XFS_MMAPLOCK_SHARED);
+	error = filemap_fault(vma, vmf);
+	xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
+
+	return error;
+}
+
+/*
+ * mmap()d file has taken write protection fault and is being made writable. We
+ * can set the page state up correctly for a writable page, which means we can
+ * do correct delalloc accounting (ENOSPC checking!) and unwritten extent
+ * mapping.
+ */
+STATIC int
+xfs_filemap_page_mkwrite(
+	struct vm_area_struct	*vma,
+	struct vm_fault		*vmf)
+{
+	struct xfs_inode	*ip = XFS_I(vma->vm_file->f_mapping->host);
+	int			error;
+
+	trace_xfs_filemap_page_mkwrite(ip);
+
+	xfs_ilock(ip, XFS_MMAPLOCK_SHARED);
+	error = block_page_mkwrite(vma, vmf, xfs_get_blocks);
+	xfs_iunlock(ip, XFS_MMAPLOCK_SHARED);
+
+	return error;
+}
+
 const struct file_operations xfs_file_operations = {
 	.llseek		= xfs_file_llseek,
 	.read		= new_sync_read,
@@ -1417,7 +1455,7 @@ const struct file_operations xfs_dir_file_operations = {
 };
 
 static const struct vm_operations_struct xfs_file_vm_ops = {
-	.fault		= filemap_fault,
+	.fault		= xfs_filemap_fault,
 	.map_pages	= filemap_map_pages,
-	.page_mkwrite	= xfs_vm_page_mkwrite,
+	.page_mkwrite	= xfs_filemap_page_mkwrite,
 };

fs/xfs/xfs_inode.c

@@ -117,24 +117,34 @@ xfs_ilock_attr_map_shared(
 }
 
 /*
- * The xfs inode contains 2 locks: a multi-reader lock called the
- * i_iolock and a multi-reader lock called the i_lock.  This routine
- * allows either or both of the locks to be obtained.
+ * The xfs inode contains 3 multi-reader locks: the i_iolock the i_mmap_lock and
+ * the i_lock.  This routine allows various combinations of the locks to be
+ * obtained.
  *
- * The 2 locks should always be ordered so that the IO lock is
- * obtained first in order to prevent deadlock.
+ * The 3 locks should always be ordered so that the IO lock is obtained first,
+ * the mmap lock second and the ilock last in order to prevent deadlock.
  *
- * ip -- the inode being locked
- * lock_flags -- this parameter indicates the inode's locks
- *       to be locked.  It can be:
- *		XFS_IOLOCK_SHARED,
- *		XFS_IOLOCK_EXCL,
- *		XFS_ILOCK_SHARED,
- *		XFS_ILOCK_EXCL,
- *		XFS_IOLOCK_SHARED | XFS_ILOCK_SHARED,
- *		XFS_IOLOCK_SHARED | XFS_ILOCK_EXCL,
- *		XFS_IOLOCK_EXCL | XFS_ILOCK_SHARED,
- *		XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL
+ * Basic locking order:
+ *
+ * i_iolock -> i_mmap_lock -> page_lock -> i_ilock
+ *
+ * mmap_sem locking order:
+ *
+ * i_iolock -> page lock -> mmap_sem
+ * mmap_sem -> i_mmap_lock -> page_lock
+ *
+ * The difference in mmap_sem locking order mean that we cannot hold the
+ * i_mmap_lock over syscall based read(2)/write(2) based IO. These IO paths can
+ * fault in pages during copy in/out (for buffered IO) or require the mmap_sem
+ * in get_user_pages() to map the user pages into the kernel address space for
+ * direct IO. Similarly the i_iolock cannot be taken inside a page fault because
+ * page faults already hold the mmap_sem.
+ *
+ * Hence to serialise fully against both syscall and mmap based IO, we need to
+ * take both the i_iolock and the i_mmap_lock. These locks should *only* be both
+ * taken in places where we need to invalidate the page cache in a race
+ * free manner (e.g. truncate, hole punch and other extent manipulation
+ * functions).
  */
 void
 xfs_ilock(
@@ -150,6 +160,8 @@ xfs_ilock(
 	 */
 	ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
 	       (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
+	ASSERT((lock_flags & (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL)) !=
+	       (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL));
 	ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
 	       (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
 	ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_DEP_MASK)) == 0);
@@ -159,6 +171,11 @@ xfs_ilock(
 	else if (lock_flags & XFS_IOLOCK_SHARED)
 		mraccess_nested(&ip->i_iolock, XFS_IOLOCK_DEP(lock_flags));
 
+	if (lock_flags & XFS_MMAPLOCK_EXCL)
+		mrupdate_nested(&ip->i_mmaplock, XFS_MMAPLOCK_DEP(lock_flags));
+	else if (lock_flags & XFS_MMAPLOCK_SHARED)
+		mraccess_nested(&ip->i_mmaplock, XFS_MMAPLOCK_DEP(lock_flags));
+
 	if (lock_flags & XFS_ILOCK_EXCL)
 		mrupdate_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
 	else if (lock_flags & XFS_ILOCK_SHARED)
@@ -191,6 +208,8 @@ xfs_ilock_nowait(
 	 */
 	ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
 	       (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
+	ASSERT((lock_flags & (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL)) !=
+	       (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL));
 	ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
 	       (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
 	ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_DEP_MASK)) == 0);
@@ -202,21 +221,35 @@ xfs_ilock_nowait(
 		if (!mrtryaccess(&ip->i_iolock))
 			goto out;
 	}
+
+	if (lock_flags & XFS_MMAPLOCK_EXCL) {
+		if (!mrtryupdate(&ip->i_mmaplock))
+			goto out_undo_iolock;
+	} else if (lock_flags & XFS_MMAPLOCK_SHARED) {
+		if (!mrtryaccess(&ip->i_mmaplock))
+			goto out_undo_iolock;
+	}
+
 	if (lock_flags & XFS_ILOCK_EXCL) {
 		if (!mrtryupdate(&ip->i_lock))
-			goto out_undo_iolock;
+			goto out_undo_mmaplock;
 	} else if (lock_flags & XFS_ILOCK_SHARED) {
 		if (!mrtryaccess(&ip->i_lock))
-			goto out_undo_iolock;
+			goto out_undo_mmaplock;
 	}
 	return 1;
 
- out_undo_iolock:
+out_undo_mmaplock:
+	if (lock_flags & XFS_MMAPLOCK_EXCL)
+		mrunlock_excl(&ip->i_mmaplock);
+	else if (lock_flags & XFS_MMAPLOCK_SHARED)
+		mrunlock_shared(&ip->i_mmaplock);
+out_undo_iolock:
 	if (lock_flags & XFS_IOLOCK_EXCL)
 		mrunlock_excl(&ip->i_iolock);
 	else if (lock_flags & XFS_IOLOCK_SHARED)
 		mrunlock_shared(&ip->i_iolock);
- out:
+out:
 	return 0;
 }
 
@@ -244,6 +277,8 @@ xfs_iunlock(
 	 */
 	ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
 	       (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
+	ASSERT((lock_flags & (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL)) !=
+	       (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL));
 	ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
 	       (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
 	ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_DEP_MASK)) == 0);
@@ -254,6 +289,11 @@ xfs_iunlock(
 	else if (lock_flags & XFS_IOLOCK_SHARED)
 		mrunlock_shared(&ip->i_iolock);
 
+	if (lock_flags & XFS_MMAPLOCK_EXCL)
+		mrunlock_excl(&ip->i_mmaplock);
+	else if (lock_flags & XFS_MMAPLOCK_SHARED)
+		mrunlock_shared(&ip->i_mmaplock);
+
 	if (lock_flags & XFS_ILOCK_EXCL)
 		mrunlock_excl(&ip->i_lock);
 	else if (lock_flags & XFS_ILOCK_SHARED)
@@ -271,11 +311,14 @@ xfs_ilock_demote(
 	xfs_inode_t		*ip,
 	uint			lock_flags)
 {
-	ASSERT(lock_flags & (XFS_IOLOCK_EXCL|XFS_ILOCK_EXCL));
-	ASSERT((lock_flags & ~(XFS_IOLOCK_EXCL|XFS_ILOCK_EXCL)) == 0);
+	ASSERT(lock_flags & (XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL|XFS_ILOCK_EXCL));
+	ASSERT((lock_flags &
+		~(XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL|XFS_ILOCK_EXCL)) == 0);
 
 	if (lock_flags & XFS_ILOCK_EXCL)
 		mrdemote(&ip->i_lock);
+	if (lock_flags & XFS_MMAPLOCK_EXCL)
+		mrdemote(&ip->i_mmaplock);
 	if (lock_flags & XFS_IOLOCK_EXCL)
 		mrdemote(&ip->i_iolock);
 
@@ -294,6 +337,12 @@ xfs_isilocked(
 		return rwsem_is_locked(&ip->i_lock.mr_lock);
 	}
 
+	if (lock_flags & (XFS_MMAPLOCK_EXCL|XFS_MMAPLOCK_SHARED)) {
+		if (!(lock_flags & XFS_MMAPLOCK_SHARED))
+			return !!ip->i_mmaplock.mr_writer;
+		return rwsem_is_locked(&ip->i_mmaplock.mr_lock);
+	}
+
 	if (lock_flags & (XFS_IOLOCK_EXCL|XFS_IOLOCK_SHARED)) {
 		if (!(lock_flags & XFS_IOLOCK_SHARED))
 			return !!ip->i_iolock.mr_writer;
@@ -314,14 +363,27 @@ int xfs_lock_delays;
 #endif
 
 /*
- * Bump the subclass so xfs_lock_inodes() acquires each lock with
- * a different value
+ * Bump the subclass so xfs_lock_inodes() acquires each lock with a different
+ * value. This shouldn't be called for page fault locking, but we also need to
+ * ensure we don't overrun the number of lockdep subclasses for the iolock or
+ * mmaplock as that is limited to 12 by the mmap lock lockdep annotations.
  */
 static inline int
 xfs_lock_inumorder(int lock_mode, int subclass)
 {
-	if (lock_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL))
+	if (lock_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)) {
+		ASSERT(subclass + XFS_LOCK_INUMORDER <
+			(1 << (XFS_MMAPLOCK_SHIFT - XFS_IOLOCK_SHIFT)));
 		lock_mode |= (subclass + XFS_LOCK_INUMORDER) << XFS_IOLOCK_SHIFT;
+	}
+
+	if (lock_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)) {
+		ASSERT(subclass + XFS_LOCK_INUMORDER <
+			(1 << (XFS_ILOCK_SHIFT - XFS_MMAPLOCK_SHIFT)));
+		lock_mode |= (subclass + XFS_LOCK_INUMORDER) <<
+							XFS_MMAPLOCK_SHIFT;
+	}
+
 	if (lock_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL))
 		lock_mode |= (subclass + XFS_LOCK_INUMORDER) << XFS_ILOCK_SHIFT;
 
@@ -440,10 +502,10 @@ xfs_lock_inodes(
 }
 
 /*
- * xfs_lock_two_inodes() can only be used to lock one type of lock
- * at a time - the iolock or the ilock, but not both at once. If
- * we lock both at once, lockdep will report false positives saying
- * we have violated locking orders.
+ * xfs_lock_two_inodes() can only be used to lock one type of lock at a time -
+ * the iolock, the mmaplock or the ilock, but not more than one at a time. If we
+ * lock more than one at a time, lockdep will report false positives saying we
+ * have violated locking orders.
  */
 void
 xfs_lock_two_inodes(
@@ -455,8 +517,12 @@ xfs_lock_two_inodes(
 	int			attempts = 0;
 	xfs_log_item_t		*lp;
 
-	if (lock_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL))
-		ASSERT((lock_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)) == 0);
+	if (lock_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)) {
+		ASSERT(!(lock_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)));
+		ASSERT(!(lock_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)));
+	} else if (lock_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL))
+		ASSERT(!(lock_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)));
+
 	ASSERT(ip0->i_ino != ip1->i_ino);
 
 	if (ip0->i_ino > ip1->i_ino) {

fs/xfs/xfs_inode.h

@@ -56,6 +56,7 @@ typedef struct xfs_inode {
 	struct xfs_inode_log_item *i_itemp;	/* logging information */
 	mrlock_t		i_lock;		/* inode lock */
 	mrlock_t		i_iolock;	/* inode IO lock */
+	mrlock_t		i_mmaplock;	/* inode mmap IO lock */
 	atomic_t		i_pincount;	/* inode pin count */
 	spinlock_t		i_flags_lock;	/* inode i_flags lock */
 	/* Miscellaneous state. */
@@ -263,15 +264,20 @@ static inline int xfs_isiflocked(struct xfs_inode *ip)
 #define	XFS_IOLOCK_SHARED	(1<<1)
 #define	XFS_ILOCK_EXCL		(1<<2)
 #define	XFS_ILOCK_SHARED	(1<<3)
+#define	XFS_MMAPLOCK_EXCL	(1<<4)
+#define	XFS_MMAPLOCK_SHARED	(1<<5)
 
 #define XFS_LOCK_MASK		(XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED \
-				| XFS_ILOCK_EXCL | XFS_ILOCK_SHARED)
+				| XFS_ILOCK_EXCL | XFS_ILOCK_SHARED \
+				| XFS_MMAPLOCK_EXCL | XFS_MMAPLOCK_SHARED)
 
 #define XFS_LOCK_FLAGS \
 	{ XFS_IOLOCK_EXCL,	"IOLOCK_EXCL" }, \
 	{ XFS_IOLOCK_SHARED,	"IOLOCK_SHARED" }, \
 	{ XFS_ILOCK_EXCL,	"ILOCK_EXCL" }, \
-	{ XFS_ILOCK_SHARED,	"ILOCK_SHARED" }
+	{ XFS_ILOCK_SHARED,	"ILOCK_SHARED" }, \
+	{ XFS_MMAPLOCK_EXCL,	"MMAPLOCK_EXCL" }, \
+	{ XFS_MMAPLOCK_SHARED,	"MMAPLOCK_SHARED" }
 
 
 /*
@@ -302,17 +308,26 @@ static inline int xfs_isiflocked(struct xfs_inode *ip)
 #define XFS_IOLOCK_SHIFT	16
 #define	XFS_IOLOCK_PARENT	(XFS_LOCK_PARENT << XFS_IOLOCK_SHIFT)
 
+#define XFS_MMAPLOCK_SHIFT	20
+
 #define XFS_ILOCK_SHIFT		24
 #define	XFS_ILOCK_PARENT	(XFS_LOCK_PARENT << XFS_ILOCK_SHIFT)
 #define	XFS_ILOCK_RTBITMAP	(XFS_LOCK_RTBITMAP << XFS_ILOCK_SHIFT)
 #define	XFS_ILOCK_RTSUM		(XFS_LOCK_RTSUM << XFS_ILOCK_SHIFT)
 
-#define XFS_IOLOCK_DEP_MASK	0x00ff0000
+#define XFS_IOLOCK_DEP_MASK	0x000f0000
+#define XFS_MMAPLOCK_DEP_MASK	0x00f00000
 #define XFS_ILOCK_DEP_MASK	0xff000000
-#define XFS_LOCK_DEP_MASK	(XFS_IOLOCK_DEP_MASK | XFS_ILOCK_DEP_MASK)
-
-#define XFS_IOLOCK_DEP(flags)	(((flags) & XFS_IOLOCK_DEP_MASK) >> XFS_IOLOCK_SHIFT)
-#define XFS_ILOCK_DEP(flags)	(((flags) & XFS_ILOCK_DEP_MASK) >> XFS_ILOCK_SHIFT)
+#define XFS_LOCK_DEP_MASK	(XFS_IOLOCK_DEP_MASK | \
+				 XFS_MMAPLOCK_DEP_MASK | \
+				 XFS_ILOCK_DEP_MASK)
+
+#define XFS_IOLOCK_DEP(flags)	(((flags) & XFS_IOLOCK_DEP_MASK) \
+					>> XFS_IOLOCK_SHIFT)
+#define XFS_MMAPLOCK_DEP(flags)	(((flags) & XFS_MMAPLOCK_DEP_MASK) \
+					>> XFS_MMAPLOCK_SHIFT)
+#define XFS_ILOCK_DEP(flags)	(((flags) & XFS_ILOCK_DEP_MASK) \
+					>> XFS_ILOCK_SHIFT)
 
 /*
  * For multiple groups support: if S_ISGID bit is set in the parent

fs/xfs/xfs_ioctl.c

@@ -631,7 +631,7 @@ xfs_ioc_space(
 
 	if (filp->f_flags & O_DSYNC)
 		flags |= XFS_PREALLOC_SYNC;
-	if (ioflags & XFS_IO_INVIS)	
+	if (ioflags & XFS_IO_INVIS)
 		flags |= XFS_PREALLOC_INVISIBLE;
 
 	error = mnt_want_write_file(filp);
@@ -643,6 +643,9 @@ xfs_ioc_space(
 	if (error)
 		goto out_unlock;
 
+	xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
+	iolock |= XFS_MMAPLOCK_EXCL;
+
 	switch (bf->l_whence) {
 	case 0: /*SEEK_SET*/
 		break;

fs/xfs/xfs_iops.c

@@ -771,6 +771,7 @@ xfs_setattr_size(
 		return error;
 
 	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
+	ASSERT(xfs_isilocked(ip, XFS_MMAPLOCK_EXCL));
 	ASSERT(S_ISREG(ip->i_d.di_mode));
 	ASSERT((iattr->ia_valid & (ATTR_UID|ATTR_GID|ATTR_ATIME|ATTR_ATIME_SET|
 		ATTR_MTIME_SET|ATTR_KILL_PRIV|ATTR_TIMES_SET)) == 0);
@@ -834,55 +835,27 @@ xfs_setattr_size(
 	inode_dio_wait(inode);
 
 	/*
-	 * Do all the page cache truncate work outside the transaction context
-	 * as the "lock" order is page lock->log space reservation.  i.e.
-	 * locking pages inside the transaction can ABBA deadlock with
-	 * writeback. We have to do the VFS inode size update before we truncate
-	 * the pagecache, however, to avoid racing with page faults beyond the
-	 * new EOF they are not serialised against truncate operations except by
-	 * page locks and size updates.
+	 * We've already locked out new page faults, so now we can safely remove
+	 * pages from the page cache knowing they won't get refaulted until we
+	 * drop the XFS_MMAP_EXCL lock after the extent manipulations are
+	 * complete. The truncate_setsize() call also cleans partial EOF page
+	 * PTEs on extending truncates and hence ensures sub-page block size
+	 * filesystems are correctly handled, too.
 	 *
-	 * Hence we are in a situation where a truncate can fail with ENOMEM
-	 * from xfs_trans_reserve(), but having already truncated the in-memory
-	 * version of the file (i.e. made user visible changes). There's not
-	 * much we can do about this, except to hope that the caller sees ENOMEM
-	 * and retries the truncate operation.
+	 * We have to do all the page cache truncate work outside the
+	 * transaction context as the "lock" order is page lock->log space
+	 * reservation as defined by extent allocation in the writeback path.
+	 * Hence a truncate can fail with ENOMEM from xfs_trans_reserve(), but
+	 * having already truncated the in-memory version of the file (i.e. made
+	 * user visible changes). There's not much we can do about this, except
+	 * to hope that the caller sees ENOMEM and retries the truncate
+	 * operation.
 	 */
 	error = block_truncate_page(inode->i_mapping, newsize, xfs_get_blocks);
 	if (error)
 		return error;
 	truncate_setsize(inode, newsize);
 
-	/*
-	 * The "we can't serialise against page faults" pain gets worse.
-	 *
-	 * If the file is mapped then we have to clean the page at the old EOF
-	 * when extending the file. Extending the file can expose changes the
-	 * underlying page mapping (e.g. from beyond EOF to a hole or
-	 * unwritten), and so on the next attempt to write to that page we need
-	 * to remap it for write. i.e. we need .page_mkwrite() to be called.
-	 * Hence we need to clean the page to clean the pte and so a new write
-	 * fault will be triggered appropriately.
-	 *
-	 * If we do it before we change the inode size, then we can race with a
-	 * page fault that maps the page with exactly the same problem. If we do
-	 * it after we change the file size, then a new page fault can come in
-	 * and allocate space before we've run the rest of the truncate
-	 * transaction. That's kinda grotesque, but it's better than have data
-	 * over a hole, and so that's the lesser evil that has been chosen here.
-	 *
-	 * The real solution, however, is to have some mechanism for locking out
-	 * page faults while a truncate is in progress.
-	 */
-	if (newsize > oldsize && mapping_mapped(VFS_I(ip)->i_mapping)) {
-		error = filemap_write_and_wait_range(
-				VFS_I(ip)->i_mapping,
-				round_down(oldsize, PAGE_CACHE_SIZE),
-				round_up(oldsize, PAGE_CACHE_SIZE) - 1);
-		if (error)
-			return error;
-	}
-
 	tp = xfs_trans_alloc(mp, XFS_TRANS_SETATTR_SIZE);
 	error = xfs_trans_reserve(tp, &M_RES(mp)->tr_itruncate, 0, 0);
 	if (error)
@@ -981,8 +954,12 @@ xfs_vn_setattr(
 
 		xfs_ilock(ip, iolock);
 		error = xfs_break_layouts(dentry->d_inode, &iolock);
-		if (!error)
+		if (!error) {
+			xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
+			iolock |= XFS_MMAPLOCK_EXCL;
+
 			error = xfs_setattr_size(ip, iattr);
+		}
 		xfs_iunlock(ip, iolock);
 	} else {
 		error = xfs_setattr_nonsize(ip, iattr, 0);

fs/xfs/xfs_super.c

@@ -966,6 +966,8 @@ xfs_fs_inode_init_once(
 	atomic_set(&ip->i_pincount, 0);
 	spin_lock_init(&ip->i_flags_lock);
 
+	mrlock_init(&ip->i_mmaplock, MRLOCK_ALLOW_EQUAL_PRI|MRLOCK_BARRIER,
+		     "xfsino", ip->i_ino);
 	mrlock_init(&ip->i_lock, MRLOCK_ALLOW_EQUAL_PRI|MRLOCK_BARRIER,
 		     "xfsino", ip->i_ino);
 }

fs/xfs/xfs_trace.h

@@ -685,6 +685,9 @@ DEFINE_INODE_EVENT(xfs_inode_set_eofblocks_tag);
 DEFINE_INODE_EVENT(xfs_inode_clear_eofblocks_tag);
 DEFINE_INODE_EVENT(xfs_inode_free_eofblocks_invalid);
 
+DEFINE_INODE_EVENT(xfs_filemap_fault);
+DEFINE_INODE_EVENT(xfs_filemap_page_mkwrite);
+
 DECLARE_EVENT_CLASS(xfs_iref_class,
 	TP_PROTO(struct xfs_inode *ip, unsigned long caller_ip),
 	TP_ARGS(ip, caller_ip),