Commit a42fa643 authored by Goldwyn Rodrigues's avatar Goldwyn Rodrigues Committed by David Sterba
Browse files

btrfs: call iomap_dio_complete() without inode_lock 



If direct writes are called with O_DIRECT | O_DSYNC, it will result in a
deadlock because iomap_dio_rw() is called under i_rwsem which calls:

  iomap_dio_complete()
    generic_write_sync()
      btrfs_sync_file()

btrfs_sync_file() requires i_rwsem, so call __iomap_dio_rw() with the
i_rwsem locked, and call iomap_dio_complete() after unlocking i_rwsem.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarGoldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 502756b3

fs/btrfs/file.c

+11 −13
Original line number Diff line number Diff line
@@ -1906,6 +1906,7 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from) 
	loff_t endbyte;

	ssize_t err;

	unsigned int ilock_flags = 0;

	struct iomap_dio *dio = NULL;



	if (iocb->ki_flags & IOCB_NOWAIT)

		ilock_flags |= BTRFS_ILOCK_TRY;
@@ -1948,22 +1949,19 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from) 
		goto buffered;

	}



	/*

	 * 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,

	dio = __iomap_dio_rw(iocb, from, &btrfs_dio_iomap_ops,

			     &btrfs_dio_ops, is_sync_kiocb(iocb));



	if (written == -ENOTBLK)

		written = 0;



	btrfs_inode_unlock(inode, ilock_flags);



	if (IS_ERR_OR_NULL(dio)) {

		err = PTR_ERR_OR_ZERO(dio);

		if (err < 0 && err != -ENOTBLK)

			goto out;

	} else {

		written = iomap_dio_complete(dio);

	}



	if (written < 0 || !iov_iter_count(from)) {

		err = written;

		goto out;