xfs: extend writeback requests to handle rt cow correctly

If we have shared realtime files and the rt extent size is larger than a
single fs block, we need to extend writeback requests to be aligned to
rt extent size granularity because we cannot share partial rt extents.
The front end should have set us up for this by dirtying the relevant
ranges.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 36 insertions, 4 deletions

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index c8c15c3c3147..e68d69022550 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -470,12 +470,41 @@ static const struct iomap_writeback_ops xfs_writeback_ops = {
 	.discard_page		= xfs_discard_page,
 };
 
+/*
+ * Extend the writeback range to allocation unit granularity and alignment.
+ * This is a requirement for blocksize > pagesize scenarios such as realtime
+ * copy on write, since we can only share full rt extents.
+ */
+static void
+xfs_vm_writepage_extend(
+	struct xfs_inode		*ip,
+	struct writeback_control	*wbc)
+{
+	unsigned int			bsize = xfs_inode_alloc_unitsize(ip);
+	long long int			pages_to_write;
+
+	wbc->range_start = rounddown_64(wbc->range_start, bsize);
+	if (wbc->range_end != LLONG_MAX)
+		wbc->range_end = roundup_64(wbc->range_end, bsize);
+
+	if (wbc->nr_to_write == LONG_MAX)
+		return;
+
+	pages_to_write = roundup_64(wbc->range_end - wbc->range_start,
+				    PAGE_SIZE);
+	if (pages_to_write >= LONG_MAX)
+		pages_to_write = LONG_MAX;
+	if (wbc->nr_to_write < pages_to_write)
+		wbc->nr_to_write = pages_to_write;
+}
+
 STATIC int
 xfs_vm_writepages(
-	struct address_space	*mapping,
-	struct writeback_control *wbc)
+	struct address_space		*mapping,
+	struct writeback_control	*wbc)
 {
-	struct xfs_writepage_ctx wpc = { };
+	struct xfs_writepage_ctx	wpc = { };
+	struct xfs_inode		*ip = XFS_I(mapping->host);
 
 	/*
 	 * Writing back data in a transaction context can result in recursive
@@ -484,7 +513,10 @@ xfs_vm_writepages(
 	if (WARN_ON_ONCE(current->journal_info))
 		return 0;
 
-	xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
+	if (xfs_inode_needs_cow_around(ip))
+		xfs_vm_writepage_extend(ip, wbc);
+
+	xfs_iflags_clear(ip, XFS_ITRUNCATED);
 	return iomap_writepages(mapping, wbc, &wpc.ctx, &xfs_writeback_ops);
 }