[PATCH 35/40] btrfs: allocate dio_data on stack

[Christoph Hellwig <hch@xxxxxx>]

Make use of the new iomap_iter->private field to avoid a memory
allocation per iomap range.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/btrfs/inode.c | 36 ++++++++++++++----------------------
 1 file changed, 14 insertions(+), 22 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ab3ff4747266a..adcd392caa78e 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7511,10 +7511,11 @@ static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
 		loff_t length, unsigned int flags, struct iomap *iomap,
 		struct iomap *srcmap)
 {
+	struct iomap_iter *iter = container_of(iomap, struct iomap_iter, iomap);
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct extent_map *em;
 	struct extent_state *cached_state = NULL;
-	struct btrfs_dio_data *dio_data = NULL;
+	struct btrfs_dio_data *dio_data = iter->private;
 	u64 lockstart, lockend;
 	const bool write = !!(flags & IOMAP_WRITE);
 	int ret = 0;
@@ -7541,21 +7542,15 @@ static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
 			return ret;
 	}
 
-	dio_data = kzalloc(sizeof(*dio_data), GFP_NOFS);
-	if (!dio_data)
-		return -ENOMEM;
-
-	iomap->private = dio_data;
-
+	dio_data->submitted = 0;
+	dio_data->data_reserved = NULL;
 
 	/*
 	 * If this errors out it's because we couldn't invalidate pagecache for
 	 * this range and we need to fallback to buffered.
 	 */
-	if (lock_extent_direct(inode, lockstart, lockend, &cached_state, write)) {
-		ret = -ENOTBLK;
-		goto err;
-	}
+	if (lock_extent_direct(inode, lockstart, lockend, &cached_state, write))
+		return -ENOTBLK;
 
 	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, len);
 	if (IS_ERR(em)) {
@@ -7664,24 +7659,22 @@ static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
 unlock_err:
 	unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
 			     &cached_state);
-err:
-	kfree(dio_data);
-
 	return ret;
 }
 
 static int btrfs_dio_iomap_end(struct inode *inode, loff_t pos, loff_t length,
 		ssize_t written, unsigned int flags, struct iomap *iomap)
 {
-	int ret = 0;
-	struct btrfs_dio_data *dio_data = iomap->private;
+	struct iomap_iter *iter = container_of(iomap, struct iomap_iter, iomap);
+	struct btrfs_dio_data *dio_data = iter->private;
 	size_t submitted = dio_data->submitted;
 	const bool write = !!(flags & IOMAP_WRITE);
+	int ret = 0;
 
 	if (!write && (iomap->type == IOMAP_HOLE)) {
 		/* If reading from a hole, unlock and return */
 		unlock_extent(&BTRFS_I(inode)->io_tree, pos, pos + length - 1);
-		goto out;
+		return 0;
 	}
 
 	if (submitted < length) {
@@ -7698,10 +7691,6 @@ static int btrfs_dio_iomap_end(struct inode *inode, loff_t pos, loff_t length,
 
 	if (write)
 		extent_changeset_free(dio_data->data_reserved);
-out:
-	kfree(dio_data);
-	iomap->private = NULL;
-
 	return ret;
 }
 
@@ -7935,7 +7924,7 @@ static void btrfs_submit_direct(const struct iomap_iter *iter,
 	int ret;
 	blk_status_t status;
 	struct btrfs_io_geometry geom;
-	struct btrfs_dio_data *dio_data = iter->iomap.private;
+	struct btrfs_dio_data *dio_data = iter->private;
 	struct extent_map *em = NULL;
 
 	dip = btrfs_create_dio_private(dio_bio, inode, file_offset);
@@ -8062,6 +8051,9 @@ static const struct iomap_dio_ops btrfs_dio_ops = {
 ssize_t btrfs_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 		size_t done_before)
 {
+	struct btrfs_dio_data data;
+
+	iocb->private = &data;
 	return iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops, &btrfs_dio_ops,
 			   IOMAP_DIO_PARTIAL, done_before);
 }
-- 
2.30.2