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Commit b0c0ea63 authored by David Sterba's avatar David Sterba
Browse files

btrfs: allocate root item at snapshot ioctl time 



The actual snapshot creation is delayed until transaction commit. If we
cannot get enough memory for the root item there, we have to fail the
whole transaction commit which is bad. So we'll allocate the memory at
the ioctl call and pass it along with the pending_snapshot struct. The
potential ENOMEM will be returned to the caller of snapshot ioctl.

Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent a1ee7362

fs/btrfs/ioctl.c

+9 −0
Original line number Diff line number Diff line
@@ -659,6 +659,13 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir, 
	if (!pending_snapshot)

		return -ENOMEM;



	pending_snapshot->root_item = kzalloc(sizeof(struct btrfs_root_item),

			GFP_NOFS);

	if (!pending_snapshot->root_item) {

		ret = -ENOMEM;

		goto free_pending;

	}



	atomic_inc(&root->will_be_snapshoted);

	smp_mb__after_atomic();

	btrfs_wait_for_no_snapshoting_writes(root);
@@ -738,6 +745,8 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir, 
dec_and_free:

	if (atomic_dec_and_test(&root->will_be_snapshoted))

		wake_up_atomic_t(&root->will_be_snapshoted);

free_pending:

	kfree(pending_snapshot->root_item);

	kfree(pending_snapshot);



	return ret;

fs/btrfs/transaction.c

+3 −6
Original line number Diff line number Diff line
@@ -1325,11 +1325,8 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, 
		return 0;

	}



	new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);

	if (!new_root_item) {

		pending->error = -ENOMEM;

		goto root_item_alloc_fail;

	}

	ASSERT(pending->root_item);

	new_root_item = pending->root_item;



	pending->error = btrfs_find_free_objectid(tree_root, &objectid);

	if (pending->error)
@@ -1562,7 +1559,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, 
	btrfs_clear_skip_qgroup(trans);

no_free_objectid:

	kfree(new_root_item);

root_item_alloc_fail:

	pending->root_item = NULL;

	btrfs_free_path(path);

	return ret;

}

fs/btrfs/transaction.h

+1 −0
Original line number Diff line number Diff line
@@ -137,6 +137,7 @@ struct btrfs_pending_snapshot { 
	struct dentry *dentry;

	struct inode *dir;

	struct btrfs_root *root;

	struct btrfs_root_item *root_item;

	struct btrfs_root *snap;

	struct btrfs_qgroup_inherit *inherit;

	/* block reservation for the operation */