btrfs: split btrfs_direct_IO to read and write

The read and write DIO don't have anything in common except for the
call to iomap_dio_rw. Extract the write call into a new function to get
rid of conditional statements for direct write.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -28,6 +28,7 @@
 #include <linux/dynamic_debug.h>
 #include <linux/refcount.h>
 #include <linux/crc32c.h>
+#include <linux/iomap.h>
 #include "extent-io-tree.h"
 #include "extent_io.h"
 #include "extent_map.h"
@@ -3065,7 +3066,9 @@ int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end);
 void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start,
 					  u64 end, int uptodate);
 extern const struct dentry_operations btrfs_dentry_operations;
-ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter);
+extern const struct iomap_ops btrfs_dio_iomap_ops;
+extern const struct iomap_dio_ops btrfs_dio_ops;
+extern const struct iomap_dio_ops btrfs_sync_dops;
 
 /* ioctl.c */
 long btrfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);

fs/btrfs/file.c

@@ -1782,21 +1782,67 @@ again:
 	return num_written ? num_written : ret;
 }
 
-static ssize_t __btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
+static ssize_t check_direct_IO(struct btrfs_fs_info *fs_info,
+			       const struct iov_iter *iter, loff_t offset)
+{
+	const u32 blocksize_mask = fs_info->sectorsize - 1;
+
+	if (offset & blocksize_mask)
+		return -EINVAL;
+
+	if (iov_iter_alignment(iter) & blocksize_mask)
+		return -EINVAL;
+
+	return 0;
+}
+
+static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file_inode(file);
-	loff_t pos;
+	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
-	ssize_t written;
+	loff_t pos = iocb->ki_pos;
+	ssize_t written = 0;
+	bool relock = false;
 	ssize_t written_buffered;
 	loff_t endbyte;
 	int err;
 
-	written = btrfs_direct_IO(iocb, from);
+	if (check_direct_IO(fs_info, from, pos))
+		goto buffered;
+
+	/*
+	 * If the write DIO is beyond EOF, we need to update the isize, but it
+	 * is protected by inode lock. So we cannot unlock it here.
+	 */
+	if (pos + iov_iter_count(from) <= inode->i_size) {
+		inode_unlock(inode);
+		relock = true;
+	}
+	down_read(&BTRFS_I(inode)->dio_sem);
+
+	/*
+	 * This is actually a sync iocb, so we need our fancy endio to know if
+	 * we need to sync.
+	 */
+	if (current->journal_info)
+		written = iomap_dio_rw(iocb, from, &btrfs_dio_iomap_ops,
+				       &btrfs_sync_dops, is_sync_kiocb(iocb));
+	else
+		written = iomap_dio_rw(iocb, from, &btrfs_dio_iomap_ops,
+				       &btrfs_dio_ops, is_sync_kiocb(iocb));
+
+	if (written == -ENOTBLK)
+		written = 0;
+
+	up_read(&BTRFS_I(inode)->dio_sem);
+	if (relock)
+		inode_lock(inode);
 
 	if (written < 0 || !iov_iter_count(from))
 		return written;
 
+buffered:
 	pos = iocb->ki_pos;
 	written_buffered = btrfs_buffered_write(iocb, from);
 	if (written_buffered < 0) {
@@ -1970,7 +2016,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 			iocb->ki_flags &= ~IOCB_DSYNC;
 			current->journal_info = BTRFS_DIO_SYNC_STUB;
 		}
-		num_written = __btrfs_direct_write(iocb, from);
+		num_written = btrfs_direct_write(iocb, from);
 
 		/*
 		 * As stated above, we cleared journal_info, so we need to do
@@ -3545,16 +3591,47 @@ static int btrfs_file_open(struct inode *inode, struct file *filp)
 	return generic_file_open(inode, filp);
 }
 
+static int check_direct_read(struct btrfs_fs_info *fs_info,
+			     const struct iov_iter *iter, loff_t offset)
+{
+	int ret;
+	int i, seg;
+
+	ret = check_direct_IO(fs_info, iter, offset);
+	if (ret < 0)
+		return ret;
+
+	if (!iter_is_iovec(iter))
+		return 0;
+
+	for (seg = 0; seg < iter->nr_segs; seg++)
+		for (i = seg + 1; i < iter->nr_segs; i++)
+			if (iter->iov[seg].iov_base == iter->iov[i].iov_base)
+				return -EINVAL;
+	return 0;
+}
+
+static ssize_t btrfs_direct_read(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+	ssize_t ret;
+
+	if (check_direct_read(btrfs_sb(inode->i_sb), to, iocb->ki_pos))
+		return 0;
+
+	inode_lock_shared(inode);
+	ret = iomap_dio_rw(iocb, to, &btrfs_dio_iomap_ops, &btrfs_dio_ops,
+			   is_sync_kiocb(iocb));
+	inode_unlock_shared(inode);
+	return ret;
+}
+
 static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
 	ssize_t ret = 0;
 
 	if (iocb->ki_flags & IOCB_DIRECT) {
-		struct inode *inode = file_inode(iocb->ki_filp);
+		ret = btrfs_direct_read(iocb, to);
-
-		inode_lock_shared(inode);
-		ret = btrfs_direct_IO(iocb, to);
-		inode_unlock_shared(inode);
 		if (ret < 0 || !iov_iter_count(to) ||
 		    iocb->ki_pos >= i_size_read(file_inode(iocb->ki_filp)))
 			return ret;

fs/btrfs/inode.c

@@ -7954,39 +7954,6 @@ out_err:
 	return BLK_QC_T_NONE;
 }
 
-static ssize_t check_direct_IO(struct btrfs_fs_info *fs_info,
-			       const struct iov_iter *iter, loff_t offset)
-{
-	int seg;
-	int i;
-	unsigned int blocksize_mask = fs_info->sectorsize - 1;
-	ssize_t retval = -EINVAL;
-
-	if (offset & blocksize_mask)
-		goto out;
-
-	if (iov_iter_alignment(iter) & blocksize_mask)
-		goto out;
-
-	/* If this is a write we don't need to check anymore */
-	if (iov_iter_rw(iter) != READ || !iter_is_iovec(iter))
-		return 0;
-	/*
-	 * Check to make sure we don't have duplicate iov_base's in this
-	 * iovec, if so return EINVAL, otherwise we'll get csum errors
-	 * when reading back.
-	 */
-	for (seg = 0; seg < iter->nr_segs; seg++) {
-		for (i = seg + 1; i < iter->nr_segs; i++) {
-			if (iter->iov[seg].iov_base == iter->iov[i].iov_base)
-				goto out;
-		}
-	}
-	retval = 0;
-out:
-	return retval;
-}
-
 static inline int btrfs_maybe_fsync_end_io(struct kiocb *iocb, ssize_t size,
 					   int error, unsigned flags)
 {
@@ -8011,72 +7978,20 @@ static inline int btrfs_maybe_fsync_end_io(struct kiocb *iocb, ssize_t size,
 	return 0;
 }
 
-static const struct iomap_ops btrfs_dio_iomap_ops = {
+const struct iomap_ops btrfs_dio_iomap_ops = {
 	.iomap_begin            = btrfs_dio_iomap_begin,
 	.iomap_end              = btrfs_dio_iomap_end,
 };
 
-static const struct iomap_dio_ops btrfs_dio_ops = {
+const struct iomap_dio_ops btrfs_dio_ops = {
 	.submit_io		= btrfs_submit_direct,
 };
 
-static const struct iomap_dio_ops btrfs_sync_dops = {
+const struct iomap_dio_ops btrfs_sync_dops = {
 	.submit_io		= btrfs_submit_direct,
 	.end_io			= btrfs_maybe_fsync_end_io,
 };
 
-ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
-{
-	struct file *file = iocb->ki_filp;
-	struct inode *inode = file->f_mapping->host;
-	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
-	struct extent_changeset *data_reserved = NULL;
-	loff_t offset = iocb->ki_pos;
-	size_t count = 0;
-	bool relock = false;
-	ssize_t ret;
-
-	if (check_direct_IO(fs_info, iter, offset))
-		return 0;
-
-	count = iov_iter_count(iter);
-	if (iov_iter_rw(iter) == WRITE) {
-		/*
-		 * If the write DIO is beyond the EOF, we need update
-		 * the isize, but it is protected by i_mutex. So we can
-		 * not unlock the i_mutex at this case.
-		 */
-		if (offset + count <= inode->i_size) {
-			inode_unlock(inode);
-			relock = true;
-		}
-		down_read(&BTRFS_I(inode)->dio_sem);
-	}
-
-	/*
-	 * We have are actually a sync iocb, so we need our fancy endio to know
-	 * if we need to sync.
-	 */
-	if (current->journal_info)
-		ret = iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops,
-				   &btrfs_sync_dops, is_sync_kiocb(iocb));
-	else
-		ret = iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops,
-				   &btrfs_dio_ops, is_sync_kiocb(iocb));
-
-	if (ret == -ENOTBLK)
-		ret = 0;
-
-	if (iov_iter_rw(iter) == WRITE)
-		up_read(&BTRFS_I(inode)->dio_sem);
-
-	if (relock)
-		inode_lock(inode);
-
-	extent_changeset_free(data_reserved);
-	return ret;
-}
-
 static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 			u64 start, u64 len)
 {