block/fs: Pass an iocb to generic_atomic_write_valid()

Darrick and Hannes both thought it better that generic_atomic_write_valid()
should be passed a struct iocb, and not just the member of that struct
which is referenced; see [0] and [1].

I think that makes a more generic and clean API, so make that change.

[0] https://lore.kernel.org/linux-block/680ce641-729b-4150-b875-531a98657682@suse.de/
[1] https://lore.kernel.org/linux-xfs/20240620212401.GA3058325@frogsfrogsfrogs/

Fixes: c34fc6f ("fs: Initial atomic write support")
Suggested-by: Darrick J. Wong <djwong@kernel.org>
Suggested-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20241019125113.369994-2-john.g.garry@oracle.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/fops.c

@@ -35,13 +35,13 @@ static blk_opf_t dio_bio_write_op(struct kiocb *iocb)
 	return opf;
 }
 
-static bool blkdev_dio_invalid(struct block_device *bdev, loff_t pos,
+static bool blkdev_dio_invalid(struct block_device *bdev, struct kiocb *iocb,
 				struct iov_iter *iter, bool is_atomic)
 {
-	if (is_atomic && !generic_atomic_write_valid(iter, pos))
+	if (is_atomic && !generic_atomic_write_valid(iocb, iter))
 		return true;
 
-	return pos & (bdev_logical_block_size(bdev) - 1) ||
+	return iocb->ki_pos & (bdev_logical_block_size(bdev) - 1) ||
 		!bdev_iter_is_aligned(bdev, iter);
 }
 
@@ -374,7 +374,7 @@ static ssize_t blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 	if (!iov_iter_count(iter))
 		return 0;
 
-	if (blkdev_dio_invalid(bdev, iocb->ki_pos, iter, is_atomic))
+	if (blkdev_dio_invalid(bdev, iocb, iter, is_atomic))
 		return -EINVAL;
 
 	nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_VECS + 1);

fs/read_write.c

@@ -1830,7 +1830,7 @@ int generic_file_rw_checks(struct file *file_in, struct file *file_out)
 	return 0;
 }
 
-bool generic_atomic_write_valid(struct iov_iter *iter, loff_t pos)
+bool generic_atomic_write_valid(struct kiocb *iocb, struct iov_iter *iter)
 {
 	size_t len = iov_iter_count(iter);
 
@@ -1840,7 +1840,7 @@ bool generic_atomic_write_valid(struct iov_iter *iter, loff_t pos)
 	if (!is_power_of_2(len))
 		return false;
 
-	if (!IS_ALIGNED(pos, len))
+	if (!IS_ALIGNED(iocb->ki_pos, len))
 		return false;
 
 	return true;

include/linux/fs.h

@@ -3721,6 +3721,6 @@ static inline bool vfs_empty_path(int dfd, const char __user *path)
 	return !c;
 }
 
-bool generic_atomic_write_valid(struct iov_iter *iter, loff_t pos);
+bool generic_atomic_write_valid(struct kiocb *iocb, struct iov_iter *iter);
 
 #endif /* _LINUX_FS_H */