[PATCH 7/7] iomap: error out on file IO when there is no inline_data buffer

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

From: Darrick J. Wong <djwong@xxxxxxxxxx>

Return IO errors if an ->iomap_begin implementation returns an
IOMAP_INLINE buffer but forgets to set the inline_data pointer.
Filesystems should never do this, but we could help fs developers (me)
fix their bugs by handling this more gracefully than crashing the
kernel.

Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
---
 fs/iomap/buffered-io.c |   15 ++++++++++-----
 fs/iomap/direct-io.c   |    3 +++
 2 files changed, 13 insertions(+), 5 deletions(-)


diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 53324b0222de6b..2e5ed4d8fa6a81 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -351,6 +351,9 @@ static int iomap_read_inline_data(const struct iomap_iter *iter,
 	size_t size = i_size_read(iter->inode) - iomap->offset;
 	size_t offset = offset_in_folio(folio, iomap->offset);
 
+	if (WARN_ON_ONCE(iomap->inline_data == NULL))
+		return -EIO;
+
 	if (folio_test_uptodate(folio))
 		return 0;
 
@@ -905,7 +908,7 @@ static bool __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
 	return true;
 }
 
-static void iomap_write_end_inline(const struct iomap_iter *iter,
+static bool iomap_write_end_inline(const struct iomap_iter *iter,
 		struct folio *folio, loff_t pos, size_t copied)
 {
 	const struct iomap *iomap = &iter->iomap;
@@ -914,12 +917,16 @@ static void iomap_write_end_inline(const struct iomap_iter *iter,
 	WARN_ON_ONCE(!folio_test_uptodate(folio));
 	BUG_ON(!iomap_inline_data_valid(iomap));
 
+	if (WARN_ON_ONCE(iomap->inline_data == NULL))
+		return false;
+
 	flush_dcache_folio(folio);
 	addr = kmap_local_folio(folio, pos);
 	memcpy(iomap_inline_data(iomap, pos), addr, copied);
 	kunmap_local(addr);
 
 	mark_inode_dirty(iter->inode);
+	return true;
 }
 
 /*
@@ -932,10 +939,8 @@ static bool iomap_write_end(struct iomap_iter *iter, size_t len, size_t copied,
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 	loff_t pos = iter->pos;
 
-	if (srcmap->type == IOMAP_INLINE) {
-		iomap_write_end_inline(iter, folio, pos, copied);
-		return true;
-	}
+	if (srcmap->type == IOMAP_INLINE)
+		return iomap_write_end_inline(iter, folio, pos, copied);
 
 	if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
 		size_t bh_written;
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 1bf450f00f01c3..03fc68eaa16c6c 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -528,6 +528,9 @@ static int iomap_dio_inline_iter(struct iomap_iter *iomi, struct iomap_dio *dio)
 	loff_t pos = iomi->pos;
 	u64 copied;
 
+	if (WARN_ON_ONCE(inline_data == NULL))
+		return -EIO;
+
 	if (WARN_ON_ONCE(!iomap_inline_data_valid(iomap)))
 		return -EIO;