[PATCH 2/5] exfat: add iomap direct I/O support

[Namjae Jeon <linkinjeon@kernel.org>]

Add iomap-based direct I/O support to the exfat filesystem. This replaces
the previous exfat_direct_IO() implementation that used
blockdev_direct_IO() with the modern iomap_dio_rw() interface.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/exfat/file.c  | 30 ++++++++++++++++++++++++++++--
 fs/exfat/inode.c | 45 +--------------------------------------------
 2 files changed, 29 insertions(+), 46 deletions(-)

diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 756846b774c4..2a9263b4433b 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -698,7 +698,13 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 			goto unlock;
 	}
 
-	ret = __generic_file_write_iter(iocb, iter);
+	if (iocb->ki_flags & IOCB_DIRECT) {
+		ret = iomap_dio_rw(iocb, iter, &exfat_write_iomap_ops,
+				&exfat_write_dio_ops, 0, NULL, 0);
+		if (ret == -ENOTBLK)
+			ret = 0;
+	} else
+		ret = __generic_file_write_iter(iocb, iter);
 	if (ret < 0)
 		goto unlock;
 
@@ -725,11 +731,31 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 static ssize_t exfat_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);
+	ssize_t ret;
 
 	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
 		return -EIO;
 
-	return generic_file_read_iter(iocb, iter);
+	inode_lock_shared(inode);
+	if (iocb->ki_flags & IOCB_DIRECT) {
+		size_t count = iov_iter_count(iter);
+
+		if ((iocb->ki_pos | count) & (inode->i_sb->s_blocksize - 1)) {
+			ret = -EINVAL;
+			goto inode_unlock;
+		}
+
+		file_accessed(iocb->ki_filp);
+		ret = iomap_dio_rw(iocb, iter, &exfat_read_iomap_ops, NULL, 0,
+				NULL, 0);
+	} else {
+		ret = generic_file_read_iter(iocb, iter);
+	}
+
+inode_unlock:
+	inode_unlock_shared(inode);
+
+	return ret;
 }
 
 static vm_fault_t exfat_page_mkwrite(struct vm_fault *vmf)
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index cc54cce65a31..2985b5d736f6 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -478,49 +478,6 @@ static int exfat_write_end(const struct kiocb *iocb,
 	return err;
 }
 
-static ssize_t exfat_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
-{
-	struct address_space *mapping = iocb->ki_filp->f_mapping;
-	struct inode *inode = mapping->host;
-	struct exfat_inode_info *ei = EXFAT_I(inode);
-	loff_t pos = iocb->ki_pos;
-	loff_t size = pos + iov_iter_count(iter);
-	int rw = iov_iter_rw(iter);
-	ssize_t ret;
-
-	/*
-	 * Need to use the DIO_LOCKING for avoiding the race
-	 * condition of exfat_get_block() and ->truncate().
-	 */
-	ret = blockdev_direct_IO(iocb, inode, iter, exfat_get_block);
-	if (ret < 0) {
-		if (rw == WRITE && ret != -EIOCBQUEUED)
-			exfat_write_failed(mapping, size);
-
-		return ret;
-	}
-
-	size = pos + ret;
-
-	if (rw == WRITE) {
-		/*
-		 * If the block had been partially written before this write,
-		 * ->valid_size will not be updated in exfat_get_block(),
-		 * update it here.
-		 */
-		if (ei->valid_size < size) {
-			ei->valid_size = size;
-			mark_inode_dirty(inode);
-		}
-	} else if (pos < ei->valid_size && ei->valid_size < size) {
-		/* zero the unwritten part in the partially written block */
-		iov_iter_revert(iter, size - ei->valid_size);
-		iov_iter_zero(size - ei->valid_size, iter);
-	}
-
-	return ret;
-}
-
 static sector_t exfat_aop_bmap(struct address_space *mapping, sector_t block)
 {
 	sector_t blocknr;
@@ -552,7 +509,7 @@ static const struct address_space_operations exfat_aops = {
 	.writepages	= exfat_writepages,
 	.write_begin	= exfat_write_begin,
 	.write_end	= exfat_write_end,
-	.direct_IO	= exfat_direct_IO,
+	.direct_IO	= noop_direct_IO,
 	.bmap		= exfat_aop_bmap,
 	.migrate_folio	= buffer_migrate_folio,
 };
-- 
2.25.1