[PATCH 2/4] FIXUP: iomap: aligning to larger than fs block size doesn't make sense

[Christoph Hellwig <hch@lst.de>]

All of the VFS and helpers assume that the file system block size must
be larger or equal to the device block size.  So doing a max of both
doesn't really make much sense.  Siplify the code in iomap_dio_bio_iter
to do a simple if/else.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/direct-io.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index ce9cbd2bace0..8d094d6f5f3e 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -336,17 +336,19 @@ static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio)
 	int nr_pages, ret = 0;
 	u64 copied = 0;
 	size_t orig_count;
-	unsigned int alignment = bdev_logical_block_size(iomap->bdev);
+	unsigned int alignment;
 
 	if ((pos | length) & (bdev_logical_block_size(iomap->bdev) - 1))
 		return -EINVAL;
 
 	/*
-	 * Align to the larger one of bdev and fs block size, to meet the
-	 * alignment requirement of both layers.
+	 * File systems that write out of place and always allocate new blocks
+	 * need each bio to be block aligned as that's the unit of allocation.
 	 */
 	if (dio->flags & IOMAP_DIO_FSBLOCK_ALIGNED)
-		alignment = max(alignment, fs_block_size);
+		alignment = fs_block_size;
+	else
+		alignment = bdev_logical_block_size(iomap->bdev);
 
 	if (dio->flags & IOMAP_DIO_WRITE) {
 		bio_opf |= REQ_OP_WRITE;
-- 
2.47.3