Commit 973a4326 authored by Mark Harmstone's avatar Mark Harmstone Committed by David Sterba
Browse files

btrfs: don't sleep in btrfs_encoded_read() if IOCB_NOWAIT is set 



Change btrfs_encoded_read() so that it returns -EAGAIN rather than sleeps
if IOCB_NOWAIT is set in iocb->ki_flags. The conditions that require
sleeping are: inode lock, writeback, extent lock, ordered range.

Signed-off-by: default avatarMark Harmstone <maharmstone@fb.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 26efd447

fs/btrfs/inode.c

+44 −11
Original line number Diff line number Diff line
@@ -8983,12 +8983,16 @@ static ssize_t btrfs_encoded_read_inline( 
	unsigned long ptr;

	void *tmp;

	ssize_t ret;

	const bool nowait = (iocb->ki_flags & IOCB_NOWAIT);



	path = btrfs_alloc_path();

	if (!path) {

		ret = -ENOMEM;

		goto out;

	}



	path->nowait = nowait;



	ret = btrfs_lookup_file_extent(NULL, root, path, btrfs_ino(inode),

				       extent_start, 0);

	if (ret) {
@@ -9198,11 +9202,15 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter, 
	size_t count = iov_iter_count(iter);

	u64 start, lockend;

	struct extent_map *em;

	const bool nowait = (iocb->ki_flags & IOCB_NOWAIT);

	bool unlocked = false;



	file_accessed(iocb->ki_filp);



	btrfs_inode_lock(inode, BTRFS_ILOCK_SHARED);

	ret = btrfs_inode_lock(inode,

			       BTRFS_ILOCK_SHARED | (nowait ? BTRFS_ILOCK_TRY : 0));

	if (ret)

		return ret;



	if (iocb->ki_pos >= inode->vfs_inode.i_size) {

		btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
@@ -9215,6 +9223,29 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter, 
	 */

	lockend = start + BTRFS_MAX_UNCOMPRESSED - 1;



	if (nowait) {

		struct btrfs_ordered_extent *ordered;



		if (filemap_range_needs_writeback(inode->vfs_inode.i_mapping,

						  start, lockend)) {

			ret = -EAGAIN;

			goto out_unlock_inode;

		}



		if (!try_lock_extent(io_tree, start, lockend, cached_state)) {

			ret = -EAGAIN;

			goto out_unlock_inode;

		}



		ordered = btrfs_lookup_ordered_range(inode, start,

						     lockend - start + 1);

		if (ordered) {

			btrfs_put_ordered_extent(ordered);

			unlock_extent(io_tree, start, lockend, cached_state);

			ret = -EAGAIN;

			goto out_unlock_inode;

		}

	} else {

		for (;;) {

			struct btrfs_ordered_extent *ordered;
@@ -9222,6 +9253,7 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter, 
						       lockend - start + 1);

			if (ret)

				goto out_unlock_inode;



			lock_extent(io_tree, start, lockend, cached_state);

			ordered = btrfs_lookup_ordered_range(inode, start,

							     lockend - start + 1);
@@ -9231,6 +9263,7 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter, 
			unlock_extent(io_tree, start, lockend, cached_state);

			cond_resched();

		}

	}



	em = btrfs_get_extent(inode, NULL, start, lockend - start + 1);

	if (IS_ERR(em)) {