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fs: Optimize Dir.deleteTree for non-deeply-nested directories
`deleteTree` now uses a stack-allocated stack for the first 16 nested directories, and then falls back to the previous implementation (which only keeps 1 directory open at a time) when it runs out of room in its stack. This allows the function to perform as well as a recursive implementation for most use-cases without needing allocation or introducing the possibility of stack overflow.
This commit is contained in:
Ryan Liptak
parent
e9889cd25f
commit
274d19575e
214
lib/std/fs.zig
214
lib/std/fs.zig
@ -2076,7 +2076,6 @@ pub const Dir = struct {
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/// this function recursively removes its entries and then tries again.
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/// This operation is not atomic on most file systems.
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pub fn deleteTree(self: Dir, sub_path: []const u8) DeleteTreeError!void {
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// First, try deleting the item as a file. This way we don't follow sym links.
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if (self.deleteFile(sub_path)) {
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return;
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} else |err| switch (err) {
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@ -2096,31 +2095,196 @@ pub const Dir = struct {
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=> |e| return e,
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}
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const StackItem = struct {
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name: []const u8,
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parent_dir: Dir,
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iter: IterableDir.Iterator,
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};
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var stack = std.BoundedArray(StackItem, 16){};
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defer {
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for (stack.slice()) |*item| {
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item.iter.dir.close();
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}
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}
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var initial_iterable_dir = self.openIterableDir(sub_path, .{ .no_follow = true }) catch |err| switch (err) {
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error.NotDir => {
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// Somehow the sub_path got changed into a file while we were trying to delete the tree.
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// This implies that the dir at the sub_path was deleted at some point so we consider this
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// as a successful delete and return.
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return;
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},
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error.FileNotFound => {
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// That's fine, we were trying to remove this directory anyway.
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return;
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},
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error.InvalidHandle,
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error.AccessDenied,
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error.SymLinkLoop,
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error.ProcessFdQuotaExceeded,
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error.NameTooLong,
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error.SystemFdQuotaExceeded,
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error.NoDevice,
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error.SystemResources,
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error.Unexpected,
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error.InvalidUtf8,
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error.BadPathName,
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error.DeviceBusy,
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=> |e| return e,
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};
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stack.appendAssumeCapacity(StackItem{
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.name = sub_path,
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.parent_dir = self,
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.iter = initial_iterable_dir.iterateAssumeFirstIteration(),
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});
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process_stack: while (stack.len != 0) {
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var top = &(stack.slice()[stack.len - 1]);
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while (try top.iter.next()) |entry| {
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var treat_as_dir = entry.kind == .Directory;
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handle_entry: while (true) {
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if (treat_as_dir) {
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if (stack.ensureUnusedCapacity(1)) {
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var iterable_dir = top.iter.dir.openIterableDir(entry.name, .{ .no_follow = true }) catch |err| switch (err) {
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error.NotDir => {
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treat_as_dir = false;
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continue :handle_entry;
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},
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error.FileNotFound => {
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// That's fine, we were trying to remove this directory anyway.
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break :handle_entry;
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},
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error.InvalidHandle,
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error.AccessDenied,
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error.SymLinkLoop,
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error.ProcessFdQuotaExceeded,
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error.NameTooLong,
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error.SystemFdQuotaExceeded,
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error.NoDevice,
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error.SystemResources,
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error.Unexpected,
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error.InvalidUtf8,
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error.BadPathName,
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error.DeviceBusy,
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=> |e| return e,
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};
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stack.appendAssumeCapacity(StackItem{
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.name = entry.name,
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.parent_dir = top.iter.dir,
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.iter = iterable_dir.iterateAssumeFirstIteration(),
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});
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continue :process_stack;
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} else |_| {
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try top.iter.dir.deleteTreeFallback(entry.name, entry.kind);
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break :handle_entry;
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}
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} else {
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if (top.iter.dir.deleteFile(entry.name)) {
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break :handle_entry;
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} else |err| switch (err) {
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error.FileNotFound => break :handle_entry,
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error.NotDir => unreachable,
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error.IsDir => {
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treat_as_dir = true;
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continue :handle_entry;
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},
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error.AccessDenied,
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error.InvalidUtf8,
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error.SymLinkLoop,
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error.NameTooLong,
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error.SystemResources,
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error.ReadOnlyFileSystem,
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error.FileSystem,
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error.FileBusy,
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error.BadPathName,
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error.Unexpected,
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=> |e| return e,
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}
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}
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}
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}
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top.parent_dir.deleteDir(top.name) catch |err| switch (err) {
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error.FileNotFound => {},
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error.DirNotEmpty => {
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// reset the iterator and try again
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top.iter.reset();
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continue :process_stack;
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},
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else => |e| return e,
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};
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top.iter.dir.close();
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_ = stack.pop();
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}
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}
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/// Fallback version of deleteTree that is less efficient but works on arbitrarily
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/// nested directories without needing recursion or allocation.
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fn deleteTreeFallback(self: Dir, sub_path: []const u8, kind_hint: File.Kind) DeleteTreeError!void {
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start_over: while (true) {
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var iterable_dir = self.openIterableDir(sub_path, .{ .no_follow = true }) catch |err| switch (err) {
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error.NotDir => {
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// Somehow the sub_path got changed into a file while we were trying to delete the tree.
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// This implies that the dir at the sub_path was deleted at some point so we consider this
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// as a successful delete and return.
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return;
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},
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error.FileNotFound => {
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// That's fine, we were trying to remove this directory anyway.
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return;
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},
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error.InvalidHandle,
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error.AccessDenied,
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error.SymLinkLoop,
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error.ProcessFdQuotaExceeded,
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error.NameTooLong,
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error.SystemFdQuotaExceeded,
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error.NoDevice,
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error.SystemResources,
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error.Unexpected,
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error.InvalidUtf8,
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error.BadPathName,
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error.DeviceBusy,
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=> |e| return e,
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var iterable_dir = iterable_dir: {
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var treat_as_dir = kind_hint == .Directory;
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handle_entry: while (true) {
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if (treat_as_dir) {
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break :iterable_dir self.openIterableDir(sub_path, .{ .no_follow = true }) catch |err| switch (err) {
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error.NotDir => {
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treat_as_dir = false;
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continue :handle_entry;
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},
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error.FileNotFound => {
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// That's fine, we were trying to remove this directory anyway.
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return;
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},
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error.InvalidHandle,
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error.AccessDenied,
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error.SymLinkLoop,
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error.ProcessFdQuotaExceeded,
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error.NameTooLong,
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error.SystemFdQuotaExceeded,
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error.NoDevice,
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error.SystemResources,
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error.Unexpected,
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error.InvalidUtf8,
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error.BadPathName,
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error.DeviceBusy,
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=> |e| return e,
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};
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} else {
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if (self.deleteFile(sub_path)) {
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return;
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} else |err| switch (err) {
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error.FileNotFound => return,
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error.NotDir => unreachable,
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error.IsDir => {
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treat_as_dir = true;
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continue :handle_entry;
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},
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error.AccessDenied,
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error.InvalidUtf8,
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error.SymLinkLoop,
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error.NameTooLong,
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error.SystemResources,
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error.ReadOnlyFileSystem,
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error.FileSystem,
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error.FileBusy,
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error.BadPathName,
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error.Unexpected,
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=> |e| return e,
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}
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}
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}
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};
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var cleanup_dir_parent: ?IterableDir = null;
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defer if (cleanup_dir_parent) |*d| d.close();
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