fs/dax: create a common implementation to break DAX layouts

Prior to freeing a block file systems supporting FS DAX must check that
the associated pages are both unmapped from user-space and not undergoing
DMA or other access from eg.  get_user_pages().  This is achieved by
unmapping the file range and scanning the FS DAX page-cache to see if any
pages within the mapping have an elevated refcount.

This is done using two functions - dax_layout_busy_page_range() which
returns a page to wait for the refcount to become idle on.  Rather than
open-code this introduce a common implementation to both unmap and wait
for the page to become idle.

Link: https://lkml.kernel.org/r/c4d381e41fc618296cee2820403c166d80599d5c.1740713401.git-series.apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Asahi Lina <lina@asahilina.net>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: linmiaohe <linmiaohe@huawei.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Michael "Camp Drill Sergeant" Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 7 insertions, 19 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 1b5613dfed7f..d4f07e02b28b 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -2735,21 +2735,17 @@ xfs_mmaplock_two_inodes_and_break_dax_layout(
 	struct xfs_inode	*ip2)
 {
 	int			error;
-	bool			retry;
 	struct page		*page;
 
 	if (ip1->i_ino > ip2->i_ino)
 		swap(ip1, ip2);
 
 again:
-	retry = false;
 	/* Lock the first inode */
 	xfs_ilock(ip1, XFS_MMAPLOCK_EXCL);
-	error = xfs_break_dax_layouts(VFS_I(ip1), &retry);
-	if (error || retry) {
+	error = xfs_break_dax_layouts(VFS_I(ip1));
+	if (error) {
 		xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL);
-		if (error == 0 && retry)
-			goto again;
 		return error;
 	}
 
@@ -2764,7 +2760,7 @@ again:
 	 * for this nested lock case.
 	 */
 	page = dax_layout_busy_page(VFS_I(ip2)->i_mapping);
-	if (page && page_ref_count(page) != 1) {
+	if (!dax_page_is_idle(page)) {
 		xfs_iunlock(ip2, XFS_MMAPLOCK_EXCL);
 		xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL);
 		goto again;
@@ -3008,19 +3004,11 @@ xfs_wait_dax_page(
 
 int
 xfs_break_dax_layouts(
-	struct inode		*inode,
-	bool			*retry)
+	struct inode		*inode)
 {
-	struct page		*page;
-
 	xfs_assert_ilocked(XFS_I(inode), XFS_MMAPLOCK_EXCL);
 
-	page = dax_layout_busy_page(inode->i_mapping);
-	if (!page)
-		return 0;
-
-	*retry = true;
-	return dax_wait_page_idle(page, xfs_wait_dax_page, inode);
+	return dax_break_layout_inode(inode, xfs_wait_dax_page);
 }
 
 int
@@ -3038,8 +3026,8 @@ xfs_break_layouts(
 		retry = false;
 		switch (reason) {
 		case BREAK_UNMAP:
-			error = xfs_break_dax_layouts(inode, &retry);
-			if (error || retry)
+			error = xfs_break_dax_layouts(inode);
+			if (error)
 				break;
 			fallthrough;
 		case BREAK_WRITE: