[RFC 5/7] block: export blkdev_atomic_write_valid() and refactor api

[Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>]

Export the blkdev_atomic_write_valid() function so that other filesystems
can call it as a part of validating the atomic write operation.

Further, refactor the api to accept a len argument instead of iov_iter to
make it easier to call from other places.

Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
---
 block/fops.c           | 18 ++++++++++--------
 include/linux/blkdev.h |  2 ++
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index 516669ad69e5..5dae95c49720 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -41,8 +41,7 @@ static bool blkdev_dio_unaligned(struct block_device *bdev, loff_t pos,
 		!bdev_iter_is_aligned(bdev, iter);
 }
 
-static bool blkdev_atomic_write_valid(struct block_device *bdev, loff_t pos,
-			      struct iov_iter *iter)
+bool blkdev_atomic_write_valid(struct block_device *bdev, loff_t pos, size_t len)
 {
 	unsigned int atomic_write_unit_min_bytes =
 			queue_atomic_write_unit_min_bytes(bdev_get_queue(bdev));
@@ -53,16 +52,17 @@ static bool blkdev_atomic_write_valid(struct block_device *bdev, loff_t pos,
 		return false;
 	if (pos % atomic_write_unit_min_bytes)
 		return false;
-	if (iov_iter_count(iter) % atomic_write_unit_min_bytes)
+	if (len % atomic_write_unit_min_bytes)
 		return false;
-	if (!is_power_of_2(iov_iter_count(iter)))
+	if (!is_power_of_2(len))
 		return false;
-	if (iov_iter_count(iter) > atomic_write_unit_max_bytes)
+	if (len > atomic_write_unit_max_bytes)
 		return false;
-	if (pos % iov_iter_count(iter))
+	if (pos % len)
 		return false;
 	return true;
 }
+EXPORT_SYMBOL_GPL(blkdev_atomic_write_valid);
 
 #define DIO_INLINE_BIO_VECS 4
 
@@ -81,7 +81,8 @@ static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb,
 	if (blkdev_dio_unaligned(bdev, pos, iter))
 		return -EINVAL;
 
-	if (atomic_write && !blkdev_atomic_write_valid(bdev, pos, iter))
+	if (atomic_write &&
+	    !blkdev_atomic_write_valid(bdev, pos, iov_iter_count(iter)))
 		return -EINVAL;
 
 	if (nr_pages <= DIO_INLINE_BIO_VECS)
@@ -348,7 +349,8 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
 	if (blkdev_dio_unaligned(bdev, pos, iter))
 		return -EINVAL;
 
-	if (atomic_write && !blkdev_atomic_write_valid(bdev, pos, iter))
+	if (atomic_write &&
+	    !blkdev_atomic_write_valid(bdev, pos, iov_iter_count(iter)))
 		return -EINVAL;
 
 	if (iocb->ki_flags & IOCB_ALLOC_CACHE)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f70988083734..5a3124fc191f 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1566,6 +1566,8 @@ static inline int early_lookup_bdev(const char *pathname, dev_t *dev)
 int freeze_bdev(struct block_device *bdev);
 int thaw_bdev(struct block_device *bdev);
 
+bool blkdev_atomic_write_valid(struct block_device *bdev, loff_t pos, size_t len);
+
 struct io_comp_batch {
 	struct request *req_list;
 	bool need_ts;
-- 
2.39.3