iomap: simplify io_flags and io_type in struct iomap_ioend

The ioend fields for distinct types of I/O are a bit complicated.
Consolidate them into a single io_flag field with it's own flags
decoupled from the iomap flags.  This also prepares for adding a new
flag that is unrelated to both of the iomap namespaces.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250206064035.2323428-3-hch@lst.de
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

3 files changed, 46 insertions, 25 deletions

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 7952bf004bdb..d8d271107e60 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1605,13 +1605,10 @@ iomap_ioend_can_merge(struct iomap_ioend *ioend, struct iomap_ioend *next)
 {
 	if (ioend->io_bio.bi_status != next->io_bio.bi_status)
 		return false;
-	if (next->io_flags & IOMAP_F_BOUNDARY)
+	if (next->io_flags & IOMAP_IOEND_BOUNDARY)
 		return false;
-	if ((ioend->io_flags & IOMAP_F_SHARED) ^
-	    (next->io_flags & IOMAP_F_SHARED))
-		return false;
-	if ((ioend->io_type == IOMAP_UNWRITTEN) ^
-	    (next->io_type == IOMAP_UNWRITTEN))
+	if ((ioend->io_flags & IOMAP_IOEND_NOMERGE_FLAGS) !=
+	    (next->io_flags & IOMAP_IOEND_NOMERGE_FLAGS))
 		return false;
 	if (ioend->io_offset + ioend->io_size != next->io_offset)
 		return false;
@@ -1709,7 +1706,8 @@ static int iomap_submit_ioend(struct iomap_writepage_ctx *wpc, int error)
 }
 
 static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
-		struct writeback_control *wbc, struct inode *inode, loff_t pos)
+		struct writeback_control *wbc, struct inode *inode, loff_t pos,
+		u16 ioend_flags)
 {
 	struct iomap_ioend *ioend;
 	struct bio *bio;
@@ -1724,8 +1722,7 @@ static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
 
 	ioend = iomap_ioend_from_bio(bio);
 	INIT_LIST_HEAD(&ioend->io_list);
-	ioend->io_type = wpc->iomap.type;
-	ioend->io_flags = wpc->iomap.flags;
+	ioend->io_flags = ioend_flags;
 	if (pos > wpc->iomap.offset)
 		wpc->iomap.flags &= ~IOMAP_F_BOUNDARY;
 	ioend->io_inode = inode;
@@ -1737,14 +1734,13 @@ static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
 	return ioend;
 }
 
-static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t pos)
+static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t pos,
+		u16 ioend_flags)
 {
-	if (wpc->iomap.offset == pos && (wpc->iomap.flags & IOMAP_F_BOUNDARY))
-		return false;
-	if ((wpc->iomap.flags & IOMAP_F_SHARED) !=
-	    (wpc->ioend->io_flags & IOMAP_F_SHARED))
+	if (ioend_flags & IOMAP_IOEND_BOUNDARY)
 		return false;
-	if (wpc->iomap.type != wpc->ioend->io_type)
+	if ((ioend_flags & IOMAP_IOEND_NOMERGE_FLAGS) !=
+	    (wpc->ioend->io_flags & IOMAP_IOEND_NOMERGE_FLAGS))
 		return false;
 	if (pos != wpc->ioend->io_offset + wpc->ioend->io_size)
 		return false;
@@ -1779,14 +1775,23 @@ static int iomap_add_to_ioend(struct iomap_writepage_ctx *wpc,
 {
 	struct iomap_folio_state *ifs = folio->private;
 	size_t poff = offset_in_folio(folio, pos);
+	unsigned int ioend_flags = 0;
 	int error;
 
-	if (!wpc->ioend || !iomap_can_add_to_ioend(wpc, pos)) {
+	if (wpc->iomap.type == IOMAP_UNWRITTEN)
+		ioend_flags |= IOMAP_IOEND_UNWRITTEN;
+	if (wpc->iomap.flags & IOMAP_F_SHARED)
+		ioend_flags |= IOMAP_IOEND_SHARED;
+	if (pos == wpc->iomap.offset && (wpc->iomap.flags & IOMAP_F_BOUNDARY))
+		ioend_flags |= IOMAP_IOEND_BOUNDARY;
+
+	if (!wpc->ioend || !iomap_can_add_to_ioend(wpc, pos, ioend_flags)) {
 new_ioend:
 		error = iomap_submit_ioend(wpc, 0);
 		if (error)
 			return error;
-		wpc->ioend = iomap_alloc_ioend(wpc, wbc, inode, pos);
+		wpc->ioend = iomap_alloc_ioend(wpc, wbc, inode, pos,
+				ioend_flags);
 	}
 
 	if (!bio_add_folio(&wpc->ioend->io_bio, folio, len, poff))
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index aa88895673d8..8e60ceeb1520 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -114,7 +114,7 @@ xfs_end_ioend(
 	 */
 	error = blk_status_to_errno(ioend->io_bio.bi_status);
 	if (unlikely(error)) {
-		if (ioend->io_flags & IOMAP_F_SHARED) {
+		if (ioend->io_flags & IOMAP_IOEND_SHARED) {
 			xfs_reflink_cancel_cow_range(ip, offset, size, true);
 			xfs_bmap_punch_delalloc_range(ip, XFS_DATA_FORK, offset,
 					offset + size);
@@ -125,9 +125,9 @@ xfs_end_ioend(
 	/*
 	 * Success: commit the COW or unwritten blocks if needed.
 	 */
-	if (ioend->io_flags & IOMAP_F_SHARED)
+	if (ioend->io_flags & IOMAP_IOEND_SHARED)
 		error = xfs_reflink_end_cow(ip, offset, size);
-	else if (ioend->io_type == IOMAP_UNWRITTEN)
+	else if (ioend->io_flags & IOMAP_IOEND_UNWRITTEN)
 		error = xfs_iomap_write_unwritten(ip, offset, size, false);
 
 	if (!error && xfs_ioend_is_append(ioend))
@@ -410,7 +410,7 @@ xfs_submit_ioend(
 	nofs_flag = memalloc_nofs_save();
 
 	/* Convert CoW extents to regular */
-	if (!status && (ioend->io_flags & IOMAP_F_SHARED)) {
+	if (!status && (ioend->io_flags & IOMAP_IOEND_SHARED)) {
 		status = xfs_reflink_convert_cow(XFS_I(ioend->io_inode),
 				ioend->io_offset, ioend->io_size);
 	}
@@ -418,8 +418,8 @@ xfs_submit_ioend(
 	memalloc_nofs_restore(nofs_flag);
 
 	/* send ioends that might require a transaction to the completion wq */
-	if (xfs_ioend_is_append(ioend) || ioend->io_type == IOMAP_UNWRITTEN ||
-	    (ioend->io_flags & IOMAP_F_SHARED))
+	if (xfs_ioend_is_append(ioend) ||
+	    (ioend->io_flags & (IOMAP_IOEND_UNWRITTEN | IOMAP_IOEND_SHARED)))
 		ioend->io_bio.bi_end_io = xfs_end_bio;
 
 	if (status)
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index dc8df4f779d4..9583f6456165 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -328,12 +328,28 @@ sector_t iomap_bmap(struct address_space *mapping, sector_t bno,
 		const struct iomap_ops *ops);
 
 /*
+ * Flags for iomap_ioend->io_flags.
+ */
+/* shared COW extent */
+#define IOMAP_IOEND_SHARED		(1U << 0)
+/* unwritten extent */
+#define IOMAP_IOEND_UNWRITTEN		(1U << 1)
+/* don't merge into previous ioend */
+#define IOMAP_IOEND_BOUNDARY		(1U << 2)
+
+/*
+ * Flags that if set on either ioend prevent the merge of two ioends.
+ * (IOMAP_IOEND_BOUNDARY also prevents merges, but only one-way)
+ */
+#define IOMAP_IOEND_NOMERGE_FLAGS \
+	(IOMAP_IOEND_SHARED | IOMAP_IOEND_UNWRITTEN)
+
+/*
  * Structure for writeback I/O completions.
  */
 struct iomap_ioend {
 	struct list_head	io_list;	/* next ioend in chain */
-	u16			io_type;
-	u16			io_flags;	/* IOMAP_F_* */
+	u16			io_flags;	/* IOMAP_IOEND_* */
 	struct inode		*io_inode;	/* file being written to */
 	size_t			io_size;	/* size of data within eof */
 	loff_t			io_offset;	/* offset in the file */