Commit 7ce22f62 authored by David Sterba's avatar David Sterba
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btrfs: use on-stack variable for block reserve in btrfs_truncate() 



We can avoid potential memory allocation failure in btrfs_truncate() as
the block reserve lifetime is limited to the scope of the function. This
requires +48 bytes on stack.

Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent ec41c345

fs/btrfs/inode.c

+10 −12
Original line number Diff line number Diff line
@@ -7606,7 +7606,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback) 
	};

	struct btrfs_root *root = inode->root;

	struct btrfs_fs_info *fs_info = root->fs_info;

	struct btrfs_block_rsv *rsv;

	struct btrfs_block_rsv rsv;

	int ret;

	struct btrfs_trans_handle *trans;

	u64 mask = fs_info->sectorsize - 1;
@@ -7648,11 +7648,9 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback) 
	 * 2) fs_info->trans_block_rsv - this will have 1 items worth left for

	 * updating the inode.

	 */

	rsv = btrfs_alloc_block_rsv(fs_info, BTRFS_BLOCK_RSV_TEMP);

	if (!rsv)

		return -ENOMEM;

	rsv->size = min_size;

	rsv->failfast = true;

	btrfs_init_metadata_block_rsv(fs_info, &rsv, BTRFS_BLOCK_RSV_TEMP);

	rsv.size = min_size;

	rsv.failfast = true;



	/*

	 * 1 for the truncate slack space
@@ -7665,7 +7663,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback) 
	}



	/* Migrate the slack space for the truncate to our reserve */

	ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv, rsv,

	ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv, &rsv,

				      min_size, false);

	/*

	 * We have reserved 2 metadata units when we started the transaction and
@@ -7677,7 +7675,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback) 
		goto out;

	}



	trans->block_rsv = rsv;

	trans->block_rsv = &rsv;



	while (1) {

		struct extent_state *cached_state = NULL;
@@ -7720,9 +7718,9 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback) 
			break;

		}



		btrfs_block_rsv_release(fs_info, rsv, -1, NULL);

		btrfs_block_rsv_release(fs_info, &rsv, -1, NULL);

		ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv,

					      rsv, min_size, false);

					      &rsv, min_size, false);

		/*

		 * We have reserved 2 metadata units when we started the

		 * transaction and min_size matches 1 unit, so this should never
@@ -7731,7 +7729,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback) 
		if (WARN_ON(ret))

			break;



		trans->block_rsv = rsv;

		trans->block_rsv = &rsv;

	}



	/*
@@ -7770,7 +7768,7 @@ static int btrfs_truncate(struct btrfs_inode *inode, bool skip_writeback) 
		btrfs_btree_balance_dirty(fs_info);

	}

out:

	btrfs_free_block_rsv(fs_info, rsv);

	btrfs_block_rsv_release(fs_info, &rsv, (u64)-1, NULL);

	/*

	 * So if we truncate and then write and fsync we normally would just

	 * write the extents that changed, which is a problem if we need to