Btrfs: fix hash overflow handling

The handling for directory crc hash overflows was fairly obscure,
split_leaf returns EOVERFLOW when we try to extend the item and that is
supposed to bubble up to userland.  For a while it did so, but along the
way we added better handling of errors and forced the FS readonly if we
hit IO errors during the directory insertion.

Along the way, we started testing only for EEXIST and the EOVERFLOW case
was dropped.  The end result is that we may force the FS readonly if we
catch a directory hash bucket overflow.

This fixes a few problem spots.  First I add tests for EOVERFLOW in the
places where we can safely just return the error up the chain.

btrfs_rename is harder though, because it tries to insert the new
directory item only after it has already unlinked anything the rename
was going to overwrite.  Rather than adding very complex logic, I added
a helper to test for the hash overflow case early while it is still safe
to bail out.

Snapshot and subvolume creation had a similar problem, so they are using
the new helper now too.

Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Reported-by: Pascal Junod <pascal@junod.info>
static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
				       u64 off, u64 olen, u64 destoff)
{
	struct inode *inode = fdentry(file)->d_inode;
	struct btrfs_root *root = BTRFS_I(inode)->root;
	struct fd src_file;
	struct inode *src;
	struct btrfs_trans_handle *trans;
	struct btrfs_path *path;
	struct extent_buffer *leaf;
	char *buf;
	struct btrfs_key key;
	u32 nritems;
	int slot;
	int ret;
	u64 len = olen;
	u64 bs = root->fs_info->sb->s_blocksize;

	/*
	 * TODO:
	 * - split compressed inline extents.  annoying: we need to
	 *   decompress into destination's address_space (the file offset
	 *   may change, so source mapping won't do), then recompress (or
	 *   otherwise reinsert) a subrange.
	 * - allow ranges within the same file to be cloned (provided
	 *   they don't overlap)?
	 */

	/* the destination must be opened for writing */
	if (!(file->f_mode & FMODE_WRITE) || (file->f_flags & O_APPEND))
		return -EINVAL;

	if (btrfs_root_readonly(root))
		return -EROFS;

	ret = mnt_want_write_file(file);
	if (ret)
		return ret;

	src_file = fdget(srcfd);
	if (!src_file.file) {
		ret = -EBADF;
		goto out_drop_write;
	}

	ret = -EXDEV;
	if (src_file.file->f_path.mnt != file->f_path.mnt)
		goto out_fput;

	src = src_file.file->f_dentry->d_inode;

	ret = -EINVAL;
	if (src == inode)
		goto out_fput;

	/* the src must be open for reading */
	if (!(src_file.file->f_mode & FMODE_READ))
		goto out_fput;

	/* don't make the dst file partly checksummed */
	if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) !=
	    (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM))
		goto out_fput;

	ret = -EISDIR;
	if (S_ISDIR(src->i_mode) || S_ISDIR(inode->i_mode))
		goto out_fput;

	ret = -EXDEV;
	if (src->i_sb != inode->i_sb)
		goto out_fput;

	ret = -ENOMEM;
	buf = vmalloc(btrfs_level_size(root, 0));
	if (!buf)
		goto out_fput;

	path = btrfs_alloc_path();
	if (!path) {
		vfree(buf);
		goto out_fput;
	}
	path->reada = 2;

	if (inode < src) {
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
		mutex_lock_nested(&src->i_mutex, I_MUTEX_CHILD);
	} else {
		mutex_lock_nested(&src->i_mutex, I_MUTEX_PARENT);
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
	}

	/* determine range to clone */
	ret = -EINVAL;
	if (off + len > src->i_size || off + len < off)
		goto out_unlock;
	if (len == 0)
		olen = len = src->i_size - off;
	/* if we extend to eof, continue to block boundary */
	if (off + len == src->i_size)
		len = ALIGN(src->i_size, bs) - off;

	/* verify the end result is block aligned */
	if (!IS_ALIGNED(off, bs) || !IS_ALIGNED(off + len, bs) ||
	    !IS_ALIGNED(destoff, bs))
		goto out_unlock;

	if (destoff > inode->i_size) {
		ret = btrfs_cont_expand(inode, inode->i_size, destoff);
		if (ret)
			goto out_unlock;
	}

	/* truncate page cache pages from target inode range */
	truncate_inode_pages_range(&inode->i_data, destoff,
				   PAGE_CACHE_ALIGN(destoff + len) - 1);

	/* do any pending delalloc/csum calc on src, one way or
	   another, and lock file content */
	while (1) {
		struct btrfs_ordered_extent *ordered;
		lock_extent(&BTRFS_I(src)->io_tree, off, off + len - 1);
		ordered = btrfs_lookup_first_ordered_extent(src, off + len - 1);
		if (!ordered &&
		    !test_range_bit(&BTRFS_I(src)->io_tree, off, off + len - 1,
				    EXTENT_DELALLOC, 0, NULL))
			break;
		unlock_extent(&BTRFS_I(src)->io_tree, off, off + len - 1);
		if (ordered)
			btrfs_put_ordered_extent(ordered);
		btrfs_wait_ordered_range(src, off, len);
	}

	/* clone data */
	key.objectid = btrfs_ino(src);
	key.type = BTRFS_EXTENT_DATA_KEY;
	key.offset = 0;

	while (1) {
		/*
		 * note the key will change type as we walk through the
		 * tree.
		 */
		ret = btrfs_search_slot(NULL, BTRFS_I(src)->root, &key, path,
				0, 0);
		if (ret < 0)
			goto out;

		nritems = btrfs_header_nritems(path->nodes[0]);
		if (path->slots[0] >= nritems) {
			ret = btrfs_next_leaf(BTRFS_I(src)->root, path);
			if (ret < 0)
				goto out;
			if (ret > 0)
				break;
			nritems = btrfs_header_nritems(path->nodes[0]);
		}
		leaf = path->nodes[0];
		slot = path->slots[0];

		btrfs_item_key_to_cpu(leaf, &key, slot);
		if (btrfs_key_type(&key) > BTRFS_EXTENT_DATA_KEY ||
		    key.objectid != btrfs_ino(src))
			break;

		if (btrfs_key_type(&key) == BTRFS_EXTENT_DATA_KEY) {
			struct btrfs_file_extent_item *extent;
			int type;
			u32 size;
			struct btrfs_key new_key;
			u64 disko = 0, diskl = 0;
			u64 datao = 0, datal = 0;
			u8 comp;
			u64 endoff;

			size = btrfs_item_size_nr(leaf, slot);
			read_extent_buffer(leaf, buf,
					   btrfs_item_ptr_offset(leaf, slot),
					   size);

			extent = btrfs_item_ptr(leaf, slot,
						struct btrfs_file_extent_item);
			comp = btrfs_file_extent_compression(leaf, extent);
			type = btrfs_file_extent_type(leaf, extent);
			if (type == BTRFS_FILE_EXTENT_REG ||
			    type == BTRFS_FILE_EXTENT_PREALLOC) {
				disko = btrfs_file_extent_disk_bytenr(leaf,
								      extent);
				diskl = btrfs_file_extent_disk_num_bytes(leaf,
								 extent);
				datao = btrfs_file_extent_offset(leaf, extent);
				datal = btrfs_file_extent_num_bytes(leaf,
								    extent);
			} else if (type == BTRFS_FILE_EXTENT_INLINE) {
				/* take upper bound, may be compressed */
				datal = btrfs_file_extent_ram_bytes(leaf,
								    extent);
			}
			btrfs_release_path(path);

			if (key.offset + datal <= off ||
			    key.offset >= off + len - 1)
				goto next;

			memcpy(&new_key, &key, sizeof(new_key));
			new_key.objectid = btrfs_ino(inode);
			if (off <= key.offset)
				new_key.offset = key.offset + destoff - off;
			else
				new_key.offset = destoff;

			/*
			 * 1 - adjusting old extent (we may have to split it)
			 * 1 - add new extent
			 * 1 - inode update
			 */
			trans = btrfs_start_transaction(root, 3);
			if (IS_ERR(trans)) {
				ret = PTR_ERR(trans);
				goto out;
			}

			if (type == BTRFS_FILE_EXTENT_REG ||
			    type == BTRFS_FILE_EXTENT_PREALLOC) {
				/*
				 *    a  | --- range to clone ---|  b
				 * | ------------- extent ------------- |
				 */

				/* substract range b */
				if (key.offset + datal > off + len)
					datal = off + len - key.offset;

				/* substract range a */
				if (off > key.offset) {
					datao += off - key.offset;
					datal -= off - key.offset;
				}

				ret = btrfs_drop_extents(trans, root, inode,
							 new_key.offset,
							 new_key.offset + datal,
							 1);
				if (ret) {
					btrfs_abort_transaction(trans, root,
								ret);
					btrfs_end_transaction(trans, root);
					goto out;
				}

				ret = btrfs_insert_empty_item(trans, root, path,
							      &new_key, size);
				if (ret) {
					btrfs_abort_transaction(trans, root,
								ret);
					btrfs_end_transaction(trans, root);
					goto out;
				}

				leaf = path->nodes[0];
				slot = path->slots[0];
				write_extent_buffer(leaf, buf,
					    btrfs_item_ptr_offset(leaf, slot),
					    size);

				extent = btrfs_item_ptr(leaf, slot,
						struct btrfs_file_extent_item);

				/* disko == 0 means it's a hole */
				if (!disko)
					datao = 0;

				btrfs_set_file_extent_offset(leaf, extent,
							     datao);
				btrfs_set_file_extent_num_bytes(leaf, extent,
								datal);
				if (disko) {
					inode_add_bytes(inode, datal);
					ret = btrfs_inc_extent_ref(trans, root,
							disko, diskl, 0,
							root->root_key.objectid,
							btrfs_ino(inode),
							new_key.offset - datao,
							0);
					if (ret) {
						btrfs_abort_transaction(trans,
									root,
									ret);
						btrfs_end_transaction(trans,
								      root);
						goto out;

					}
				}
			} else if (type == BTRFS_FILE_EXTENT_INLINE) {
				u64 skip = 0;
				u64 trim = 0;
				if (off > key.offset) {
					skip = off - key.offset;
					new_key.offset += skip;
				}

				if (key.offset + datal > off + len)
					trim = key.offset + datal - (off + len);

				if (comp && (skip || trim)) {
					ret = -EINVAL;
					btrfs_end_transaction(trans, root);
					goto out;
				}
				size -= skip + trim;
				datal -= skip + trim;

				ret = btrfs_drop_extents(trans, root, inode,
							 new_key.offset,
							 new_key.offset + datal,
							 1);
				if (ret) {
					btrfs_abort_transaction(trans, root,
								ret);
					btrfs_end_transaction(trans, root);
					goto out;
				}

				ret = btrfs_insert_empty_item(trans, root, path,
							      &new_key, size);
				if (ret) {
					btrfs_abort_transaction(trans, root,
								ret);
					btrfs_end_transaction(trans, root);
					goto out;
				}

				if (skip) {
					u32 start =
					  btrfs_file_extent_calc_inline_size(0);
					memmove(buf+start, buf+start+skip,
						datal);
				}

				leaf = path->nodes[0];
				slot = path->slots[0];
				write_extent_buffer(leaf, buf,
					    btrfs_item_ptr_offset(leaf, slot),
					    size);
				inode_add_bytes(inode, datal);
			}

			btrfs_mark_buffer_dirty(leaf);
			btrfs_release_path(path);

			inode_inc_iversion(inode);
			inode->i_mtime = inode->i_ctime = CURRENT_TIME;

			/*
			 * we round up to the block size at eof when
			 * determining which extents to clone above,
			 * but shouldn't round up the file size
			 */
			endoff = new_key.offset + datal;
			if (endoff > destoff+olen)
				endoff = destoff+olen;
			if (endoff > inode->i_size)
				btrfs_i_size_write(inode, endoff);

			ret = btrfs_update_inode(trans, root, inode);
			if (ret) {
				btrfs_abort_transaction(trans, root, ret);
				btrfs_end_transaction(trans, root);
				goto out;
			}
			ret = btrfs_end_transaction(trans, root);
		}
next:
		btrfs_release_path(path);
		key.offset++;
	}
	ret = 0;
out:
	btrfs_release_path(path);
	unlock_extent(&BTRFS_I(src)->io_tree, off, off + len - 1);
out_unlock:
	mutex_unlock(&src->i_mutex);
	mutex_unlock(&inode->i_mutex);
	vfree(buf);
	btrfs_free_path(path);
out_fput:
	fdput(src_file);
out_drop_write:
	mnt_drop_write_file(file);
	return ret;
}

static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
				       u64 off, u64 olen, u64 destoff)
{
	struct inode *inode = fdentry(file)->d_inode;
	struct btrfs_root *root = BTRFS_I(inode)->root;
	struct fd src_file;
	struct inode *src;
	struct btrfs_trans_handle *trans;
	struct btrfs_path *path;
	struct extent_buffer *leaf;
	char *buf;
	struct btrfs_key key;
	u32 nritems;
	int slot;
	int ret;
	u64 len = olen;
	u64 bs = root->fs_info->sb->s_blocksize;

	/*
	 * TODO:
	 * - split compressed inline extents.  annoying: we need to
	 *   decompress into destination's address_space (the file offset
	 *   may change, so source mapping won't do), then recompress (or
	 *   otherwise reinsert) a subrange.
	 * - allow ranges within the same file to be cloned (provided
	 *   they don't overlap)?
	 */

	/* the destination must be opened for writing */
	if (!(file->f_mode & FMODE_WRITE) || (file->f_flags & O_APPEND))
		return -EINVAL;

	if (btrfs_root_readonly(root))
		return -EROFS;

	ret = mnt_want_write_file(file);
	if (ret)
		return ret;

	src_file = fdget(srcfd);
	if (!src_file.file) {
		ret = -EBADF;
		goto out_drop_write;
	}

	ret = -EXDEV;
	if (src_file.file->f_path.mnt != file->f_path.mnt)
		goto out_fput;

	src = src_file.file->f_dentry->d_inode;

	ret = -EINVAL;
	if (src == inode)
		goto out_fput;

	/* the src must be open for reading */
	if (!(src_file.file->f_mode & FMODE_READ))
		goto out_fput;

	/* don't make the dst file partly checksummed */
	if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) !=
	    (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM))
		goto out_fput;

	ret = -EISDIR;
	if (S_ISDIR(src->i_mode) || S_ISDIR(inode->i_mode))
		goto out_fput;

	ret = -EXDEV;
	if (src->i_sb != inode->i_sb)
		goto out_fput;

	ret = -ENOMEM;
	buf = vmalloc(btrfs_level_size(root, 0));
	if (!buf)
		goto out_fput;

	path = btrfs_alloc_path();
	if (!path) {
		vfree(buf);
		goto out_fput;
	}
	path->reada = 2;

	if (inode < src) {
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
		mutex_lock_nested(&src->i_mutex, I_MUTEX_CHILD);
	} else {
		mutex_lock_nested(&src->i_mutex, I_MUTEX_PARENT);
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
	}

	/* determine range to clone */
	ret = -EINVAL;
	if (off + len > src->i_size || off + len < off)
		goto out_unlock;
	if (len == 0)
		olen = len = src->i_size - off;
	/* if we extend to eof, continue to block boundary */
	if (off + len == src->i_size)
		len = ALIGN(src->i_size, bs) - off;

	/* verify the end result is block aligned */
	if (!IS_ALIGNED(off, bs) || !IS_ALIGNED(off + len, bs) ||
	    !IS_ALIGNED(destoff, bs))
		goto out_unlock;

	if (destoff > inode->i_size) {
		ret = btrfs_cont_expand(inode, inode->i_size, destoff);
		if (ret)
			goto out_unlock;
	}

	/* truncate page cache pages from target inode range */
	truncate_inode_pages_range(&inode->i_data, destoff,
				   PAGE_CACHE_ALIGN(destoff + len) - 1);

	/* do any pending delalloc/csum calc on src, one way or
	   another, and lock file content */
	while (1) {
		struct btrfs_ordered_extent *ordered;
		lock_extent(&BTRFS_I(src)->io_tree, off, off + len - 1);
		ordered = btrfs_lookup_first_ordered_extent(src, off + len - 1);
		if (!ordered &&
		    !test_range_bit(&BTRFS_I(src)->io_tree, off, off + len - 1,
				    EXTENT_DELALLOC, 0, NULL))
			break;
		unlock_extent(&BTRFS_I(src)->io_tree, off, off + len - 1);
		if (ordered)
			btrfs_put_ordered_extent(ordered);
		btrfs_wait_ordered_range(src, off, len);
	}

	/* clone data */
	key.objectid = btrfs_ino(src);
	key.type = BTRFS_EXTENT_DATA_KEY;
	key.offset = 0;

	while (1) {
		/*
		 * note the key will change type as we walk through the
		 * tree.
		 */
		ret = btrfs_search_slot(NULL, BTRFS_I(src)->root, &key, path,
				0, 0);
		if (ret < 0)
			goto out;

		nritems = btrfs_header_nritems(path->nodes[0]);
		if (path->slots[0] >= nritems) {
			ret = btrfs_next_leaf(BTRFS_I(src)->root, path);
			if (ret < 0)
				goto out;
			if (ret > 0)
				break;
			nritems = btrfs_header_nritems(path->nodes[0]);
		}
		leaf = path->nodes[0];
		slot = path->slots[0];

		btrfs_item_key_to_cpu(leaf, &key, slot);
		if (btrfs_key_type(&key) > BTRFS_EXTENT_DATA_KEY ||
		    key.objectid != btrfs_ino(src))
			break;

		if (btrfs_key_type(&key) == BTRFS_EXTENT_DATA_KEY) {
			struct btrfs_file_extent_item *extent;
			int type;
			u32 size;
			struct btrfs_key new_key;
			u64 disko = 0, diskl = 0;
			u64 datao = 0, datal = 0;
			u8 comp;
			u64 endoff;

			size = btrfs_item_size_nr(leaf, slot);
			read_extent_buffer(leaf, buf,
					   btrfs_item_ptr_offset(leaf, slot),
					   size);

			extent = btrfs_item_ptr(leaf, slot,
						struct btrfs_file_extent_item);
			comp = btrfs_file_extent_compression(leaf, extent);
			type = btrfs_file_extent_type(leaf, extent);
			if (type == BTRFS_FILE_EXTENT_REG ||
			    type == BTRFS_FILE_EXTENT_PREALLOC) {
				disko = btrfs_file_extent_disk_bytenr(leaf,
								      extent);
				diskl = btrfs_file_extent_disk_num_bytes(leaf,
								 extent);
				datao = btrfs_file_extent_offset(leaf, extent);
				datal = btrfs_file_extent_num_bytes(leaf,
								    extent);
			} else if (type == BTRFS_FILE_EXTENT_INLINE) {
				/* take upper bound, may be compressed */
				datal = btrfs_file_extent_ram_bytes(leaf,
								    extent);
			}
			btrfs_release_path(path);

			if (key.offset + datal <= off ||
			    key.offset >= off + len - 1)
				goto next;

			memcpy(&new_key, &key, sizeof(new_key));
			new_key.objectid = btrfs_ino(inode);
			if (off <= key.offset)
				new_key.offset = key.offset + destoff - off;
			else
				new_key.offset = destoff;

			/*
			 * 1 - adjusting old extent (we may have to split it)
			 * 1 - add new extent
			 * 1 - inode update
			 */
			trans = btrfs_start_transaction(root, 3);
			if (IS_ERR(trans)) {
				ret = PTR_ERR(trans);
				goto out;
			}

			if (type == BTRFS_FILE_EXTENT_REG ||
			    type == BTRFS_FILE_EXTENT_PREALLOC) {
				/*
				 *    a  | --- range to clone ---|  b
				 * | ------------- extent ------------- |
				 */

				/* substract range b */
				if (key.offset + datal > off + len)
					datal = off + len - key.offset;

				/* substract range a */
				if (off > key.offset) {
					datao += off - key.offset;
					datal -= off - key.offset;
				}

				ret = btrfs_drop_extents(trans, root, inode,
							 new_key.offset,
							 new_key.offset + datal,
							 1);
				if (ret) {
					btrfs_abort_transaction(trans, root,
								ret);
					btrfs_end_transaction(trans, root);
					goto out;
				}

				ret = btrfs_insert_empty_item(trans, root, path,
							      &new_key, size);
				if (ret) {
					btrfs_abort_transaction(trans, root,
								ret);
					btrfs_end_transaction(trans, root);
					goto out;
				}

				leaf = path->nodes[0];
				slot = path->slots[0];
				write_extent_buffer(leaf, buf,
					    btrfs_item_ptr_offset(leaf, slot),
					    size);

				extent = btrfs_item_ptr(leaf, slot,
						struct btrfs_file_extent_item);

				/* disko == 0 means it's a hole */
				if (!disko)
					datao = 0;

				btrfs_set_file_extent_offset(leaf, extent,
							     datao);
				btrfs_set_file_extent_num_bytes(leaf, extent,
								datal);
				if (disko) {
					inode_add_bytes(inode, datal);
					ret = btrfs_inc_extent_ref(trans, root,
							disko, diskl, 0,
							root->root_key.objectid,
							btrfs_ino(inode),
							new_key.offset - datao,
							0);
					if (ret) {
						btrfs_abort_transaction(trans,
									root,
									ret);
						btrfs_end_transaction(trans,
								      root);
						goto out;

					}
				}
			} else if (type == BTRFS_FILE_EXTENT_INLINE) {
				u64 skip = 0;
				u64 trim = 0;
				if (off > key.offset) {
					skip = off - key.offset;
					new_key.offset += skip;
				}

				if (key.offset + datal > off + len)
					trim = key.offset + datal - (off + len);

				if (comp && (skip || trim)) {
					ret = -EINVAL;
					btrfs_end_transaction(trans, root);
					goto out;
				}
				size -= skip + trim;
				datal -= skip + trim;

				ret = btrfs_drop_extents(trans, root, inode,
							 new_key.offset,
							 new_key.offset + datal,
							 1);
				if (ret) {
					btrfs_abort_transaction(trans, root,
								ret);
					btrfs_end_transaction(trans, root);
					goto out;
				}

				ret = btrfs_insert_empty_item(trans, root, path,
							      &new_key, size);
				if (ret) {
					btrfs_abort_transaction(trans, root,
								ret);
					btrfs_end_transaction(trans, root);
					goto out;
				}

				if (skip) {
					u32 start =
					  btrfs_file_extent_calc_inline_size(0);
					memmove(buf+start, buf+start+skip,
						datal);
				}

				leaf = path->nodes[0];
				slot = path->slots[0];
				write_extent_buffer(leaf, buf,
					    btrfs_item_ptr_offset(leaf, slot),
					    size);
				inode_add_bytes(inode, datal);
			}

			btrfs_mark_buffer_dirty(leaf);
			btrfs_release_path(path);

			inode_inc_iversion(inode);
			inode->i_mtime = inode->i_ctime = CURRENT_TIME;

			/*
			 * we round up to the block size at eof when
			 * determining which extents to clone above,
			 * but shouldn't round up the file size
			 */
			endoff = new_key.offset + datal;
			if (endoff > destoff+olen)
				endoff = destoff+olen;
			if (endoff > inode->i_size)
				btrfs_i_size_write(inode, endoff);

			ret = btrfs_update_inode(trans, root, inode);
			if (ret) {
				btrfs_abort_transaction(trans, root, ret);
				btrfs_end_transaction(trans, root);
				goto out;
			}
			ret = btrfs_end_transaction(trans, root);
		}
next:
		btrfs_release_path(path);
		key.offset++;
	}
	ret = 0;
out:
	btrfs_release_path(path);
	unlock_extent(&BTRFS_I(src)->io_tree, off, off + len - 1);
out_unlock:
	mutex_unlock(&src->i_mutex);
	mutex_unlock(&inode->i_mutex);
	vfree(buf);
	btrfs_free_path(path);
out_fput:
	fdput(src_file);
out_drop_write:
	mnt_drop_write_file(file);
	return ret;
}
