[PATCH v6 12/15] xfs: require mmap lock for xfs_break_layouts()

[Dan Williams]

In preparation for adding coordination between truncate operations and
busy dax-pages, extend xfs_break_layouts() to assume it must be called
with the mmap lock held. This locking scheme will be required for
coordinating the break of 'dax layouts' (non-idle dax (ZONE_DEVICE)
pages mapped into the file's address space).

Cc: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Suggested-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 fs/xfs/xfs_file.c  |   14 +++++++++-----
 fs/xfs/xfs_ioctl.c |    5 +----
 fs/xfs/xfs_iops.c  |   10 +++++++---
 fs/xfs/xfs_pnfs.c  |    6 ++++--
 4 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 9ea08326f876..ba969019bf26 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -350,9 +350,16 @@ xfs_file_aio_write_checks(
 	if (error <= 0)
 		return error;
 
+	xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
+	*iolock |= XFS_MMAPLOCK_EXCL;
 	error = xfs_break_layouts(inode, iolock);
-	if (error)
+	if (error) {
+		*iolock &= ~XFS_MMAPLOCK_EXCL;
+		xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
 		return error;
+	}
+	xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
+	*iolock &= ~XFS_MMAPLOCK_EXCL;
 
 	/*
 	 * For changing security info in file_remove_privs() we need i_rwsem
@@ -768,7 +775,7 @@ xfs_file_fallocate(
 	struct xfs_inode	*ip = XFS_I(inode);
 	long			error;
 	enum xfs_prealloc_flags	flags = 0;
-	uint			iolock = XFS_IOLOCK_EXCL;
+	uint			iolock = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
 	loff_t			new_size = 0;
 	bool			do_file_insert = false;
 
@@ -782,9 +789,6 @@ 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)
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 89fb1eb80aae..4151fade4bb1 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -614,7 +614,7 @@ xfs_ioc_space(
 	struct xfs_inode	*ip = XFS_I(inode);
 	struct iattr		iattr;
 	enum xfs_prealloc_flags	flags = 0;
-	uint			iolock = XFS_IOLOCK_EXCL;
+	uint			iolock = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
 	int			error;
 
 	/*
@@ -648,9 +648,6 @@ 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;
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 951e84df5576..d23aa08426f9 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1028,13 +1028,17 @@ xfs_vn_setattr(
 
 	if (iattr->ia_valid & ATTR_SIZE) {
 		struct xfs_inode	*ip = XFS_I(d_inode(dentry));
-		uint			iolock = XFS_IOLOCK_EXCL;
+		uint			iolock;
+
+		xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
+		iolock = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
 
 		error = xfs_break_layouts(d_inode(dentry), &iolock);
-		if (error)
+		if (error) {
+			xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
 			return error;
+		}
 
-		xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
 		error = xfs_vn_setattr_size(dentry, iattr);
 		xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
 	} else {
diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index aa6c5c193f45..9fe661c2d59c 100644
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -38,12 +38,14 @@ xfs_break_layouts(
 	struct xfs_inode	*ip = XFS_I(inode);
 	int			error;
 
-	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL));
+	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL
+				| XFS_MMAPLOCK_EXCL));
 
 	while ((error = break_layout(inode, false) == -EWOULDBLOCK)) {
 		xfs_iunlock(ip, *iolock);
 		error = break_layout(inode, true);
-		*iolock = XFS_IOLOCK_EXCL;
+		*iolock &= ~XFS_IOLOCK_SHARED;
+		*iolock |= XFS_IOLOCK_EXCL;
 		xfs_ilock(ip, *iolock);
 	}