Commit 37fad949 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: snapshot_create_lock 



Add a new lock for snapshot creation - this addresses a few races with
logged operations and snapshot deletion.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent 1e2d3999

fs/bcachefs/bcachefs.h

+1 −0
Original line number Diff line number Diff line
@@ -746,6 +746,7 @@ struct bch_fs { 
	struct snapshot_table __rcu *snapshots;

	size_t			snapshot_table_size;

	struct mutex		snapshot_table_lock;

	struct rw_semaphore	snapshot_create_lock;



	struct work_struct	snapshot_delete_work;

	struct work_struct	snapshot_wait_for_pagecache_and_delete_work;

fs/bcachefs/fs-ioctl.c

+12 −2
Original line number Diff line number Diff line
@@ -318,7 +318,7 @@ static int bch2_ioc_goingdown(struct bch_fs *c, u32 __user *arg) 
	return ret;

}



static long bch2_ioctl_subvolume_create(struct bch_fs *c, struct file *filp,

static long __bch2_ioctl_subvolume_create(struct bch_fs *c, struct file *filp,

					  struct bch_ioctl_subvolume arg)

{

	struct inode *dir;
@@ -440,6 +440,16 @@ static long bch2_ioctl_subvolume_create(struct bch_fs *c, struct file *filp, 
	return error;

}



static long bch2_ioctl_subvolume_create(struct bch_fs *c, struct file *filp,

					struct bch_ioctl_subvolume arg)

{

	down_write(&c->snapshot_create_lock);

	long ret = __bch2_ioctl_subvolume_create(c, filp, arg);

	up_write(&c->snapshot_create_lock);



	return ret;

}



static long bch2_ioctl_subvolume_destroy(struct bch_fs *c, struct file *filp,

				struct bch_ioctl_subvolume arg)

{

fs/bcachefs/io_misc.c

+20 −2
Original line number Diff line number Diff line
@@ -287,9 +287,18 @@ int bch2_truncate(struct bch_fs *c, subvol_inum inum, u64 new_i_size, u64 *i_sec 
	op.v.inum	= cpu_to_le64(inum.inum);

	op.v.new_i_size	= cpu_to_le64(new_i_size);



	return bch2_trans_run(c,

	/*

	 * Logged ops aren't atomic w.r.t. snapshot creation: creating a

	 * snapshot while they're in progress, then crashing, will result in the

	 * resume only proceeding in one of the snapshots

	 */

	down_read(&c->snapshot_create_lock);

	int ret = bch2_trans_run(c,

		bch2_logged_op_start(trans, &op.k_i) ?:

		__bch2_resume_logged_op_truncate(trans, &op.k_i, i_sectors_delta));

	up_read(&c->snapshot_create_lock);



	return ret;

}



/* finsert/fcollapse: */
@@ -491,7 +500,16 @@ int bch2_fcollapse_finsert(struct bch_fs *c, subvol_inum inum, 
	op.v.src_offset	= cpu_to_le64(offset);

	op.v.pos	= cpu_to_le64(insert ? U64_MAX : offset);



	return bch2_trans_run(c,

	/*

	 * Logged ops aren't atomic w.r.t. snapshot creation: creating a

	 * snapshot while they're in progress, then crashing, will result in the

	 * resume only proceeding in one of the snapshots

	 */

	down_read(&c->snapshot_create_lock);

	int ret = bch2_trans_run(c,

		bch2_logged_op_start(trans, &op.k_i) ?:

		__bch2_resume_logged_op_finsert(trans, &op.k_i, i_sectors_delta));

	up_read(&c->snapshot_create_lock);



	return ret;

}

fs/bcachefs/snapshot.c

+10 −3
Original line number Diff line number Diff line
@@ -1447,6 +1447,8 @@ int bch2_delete_dead_snapshots(struct bch_fs *c) 
		}

	}



	down_write(&c->snapshot_create_lock);



	for_each_btree_key(trans, iter, BTREE_ID_snapshots,

			   POS_MIN, 0, k, ret) {

		u32 snapshot = k.k->p.offset;
@@ -1457,6 +1459,9 @@ int bch2_delete_dead_snapshots(struct bch_fs *c) 
	}

	bch2_trans_iter_exit(trans, &iter);



	if (ret)

		goto err_create_lock;



	/*

	 * Fixing children of deleted snapshots can't be done completely

	 * atomically, if we crash between here and when we delete the interior
@@ -1467,14 +1472,14 @@ int bch2_delete_dead_snapshots(struct bch_fs *c) 
				  NULL, NULL, BTREE_INSERT_NOFAIL,

		bch2_fix_child_of_deleted_snapshot(trans, &iter, k, &deleted_interior));

	if (ret)

		goto err;

		goto err_create_lock;



	darray_for_each(deleted, i) {

		ret = commit_do(trans, NULL, NULL, 0,

			bch2_snapshot_node_delete(trans, *i));

		if (ret) {

			bch_err_msg(c, ret, "deleting snapshot %u", *i);

			goto err;

			goto err_create_lock;

		}

	}
@@ -1483,11 +1488,13 @@ int bch2_delete_dead_snapshots(struct bch_fs *c) 
			bch2_snapshot_node_delete(trans, *i));

		if (ret) {

			bch_err_msg(c, ret, "deleting snapshot %u", *i);

			goto err;

			goto err_create_lock;

		}

	}



	clear_bit(BCH_FS_HAVE_DELETED_SNAPSHOTS, &c->flags);

err_create_lock:

	up_write(&c->snapshot_create_lock);

err:

	darray_exit(&deleted_interior);

	darray_exit(&deleted);

fs/bcachefs/super.c

+1 −0
Original line number Diff line number Diff line
@@ -720,6 +720,7 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts) 


	mutex_init(&c->bio_bounce_pages_lock);

	mutex_init(&c->snapshot_table_lock);

	init_rwsem(&c->snapshot_create_lock);



	spin_lock_init(&c->btree_write_error_lock);