btrfs: add BTRFS_IOC_ENCODED_WRITE

The implementation resembles direct I/O: we have to flush any ordered
extents, invalidate the page cache, and do the io tree/delalloc/extent
map/ordered extent dance. From there, we can reuse the compression code
with a minor modification to distinguish the write from writeback. This
also creates inline extents when possible.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 53 insertions, 11 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 7b4a5458ca9b..c7a56909be8c 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2037,12 +2037,43 @@ out:
 	return err < 0 ? err : written;
 }
 
-static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
-				    struct iov_iter *from)
+static ssize_t btrfs_encoded_write(struct kiocb *iocb, struct iov_iter *from,
+			const struct btrfs_ioctl_encoded_io_args *encoded)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(file);
+	loff_t count;
+	ssize_t ret;
+
+	btrfs_inode_lock(inode, 0);
+	count = encoded->len;
+	ret = generic_write_checks_count(iocb, &count);
+	if (ret == 0 && count != encoded->len) {
+		/*
+		 * The write got truncated by generic_write_checks_count(). We
+		 * can't do a partial encoded write.
+		 */
+		ret = -EFBIG;
+	}
+	if (ret || encoded->len == 0)
+		goto out;
+
+	ret = btrfs_write_check(iocb, from, encoded->len);
+	if (ret < 0)
+		goto out;
+
+	ret = btrfs_do_encoded_write(iocb, from, encoded);
+out:
+	btrfs_inode_unlock(inode, 0);
+	return ret;
+}
+
+ssize_t btrfs_do_write_iter(struct kiocb *iocb, struct iov_iter *from,
+			    const struct btrfs_ioctl_encoded_io_args *encoded)
 {
 	struct file *file = iocb->ki_filp;
 	struct btrfs_inode *inode = BTRFS_I(file_inode(file));
-	ssize_t num_written = 0;
+	ssize_t num_written, num_sync;
 	const bool sync = iocb->ki_flags & IOCB_DSYNC;
 
 	/*
@@ -2053,22 +2084,28 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 	if (BTRFS_FS_ERROR(inode->root->fs_info))
 		return -EROFS;
 
-	if (!(iocb->ki_flags & IOCB_DIRECT) &&
-	    (iocb->ki_flags & IOCB_NOWAIT))
+	if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
 		return -EOPNOTSUPP;
 
 	if (sync)
 		atomic_inc(&inode->sync_writers);
 
-	if (iocb->ki_flags & IOCB_DIRECT)
-		num_written = btrfs_direct_write(iocb, from);
-	else
-		num_written = btrfs_buffered_write(iocb, from);
+	if (encoded) {
+		num_written = btrfs_encoded_write(iocb, from, encoded);
+		num_sync = encoded->len;
+	} else if (iocb->ki_flags & IOCB_DIRECT) {
+		num_written = num_sync = btrfs_direct_write(iocb, from);
+	} else {
+		num_written = num_sync = btrfs_buffered_write(iocb, from);
+	}
 
 	btrfs_set_inode_last_sub_trans(inode);
 
-	if (num_written > 0)
-		num_written = generic_write_sync(iocb, num_written);
+	if (num_sync > 0) {
+		num_sync = generic_write_sync(iocb, num_sync);
+		if (num_sync < 0)
+			num_written = num_sync;
+	}
 
 	if (sync)
 		atomic_dec(&inode->sync_writers);
@@ -2077,6 +2114,11 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 	return num_written;
 }
 
+static ssize_t btrfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	return btrfs_do_write_iter(iocb, from, NULL);
+}
+
 int btrfs_release_file(struct inode *inode, struct file *filp)
 {
 	struct btrfs_file_private *private = filp->private_data;