A call into JS can schedule another operation on the same `uv_dir_t`.
In particular, when the handle is closed from the callback for a
directory read operation, there previously was a race condition window:
1. A `dir.read()` operation is submitted to libuv
2. The read operation is finished by libuv, calling `AfterDirRead()`
3. We call into JS
4. JS calls dir.close()
5. libuv posts the close request to a thread in the pool
6. The close request runs, destroying the directory handle
7. `AfterDirRead()` is being exited.
Exiting the `FSReqAfterScope` in step 7 attempts to destroy the original
uv_fs_t` from step 1, which now points to an `uv_dir_t` that has
already been destroyed in step 5.
By forcing the `FSReqAfterScope` to clean up before we call into JS,
we can be sure that no other operations on the same `uv_dir_t` are
submitted concurrently.
This addresses issues observed when running with ASAN/valgrind.
PR-URL: https://github.com/nodejs/node/pull/33274
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
This adds long-requested methods for asynchronously interacting and
iterating through directory entries by using `uv_fs_opendir`,
`uv_fs_readdir`, and `uv_fs_closedir`.
`fs.opendir()` and friends return an `fs.Dir`, which contains methods
for doing reads and cleanup. `fs.Dir` also has the async iterator
symbol exposed.
The `read()` method and friends only return `fs.Dirent`s for this API.
Having a entry type or doing a `stat` call is deemed to be necessary in
the majority of cases, so just returning dirents seems like the logical
choice for a new api.
Reading when there are no more entries returns `null` instead of a
dirent. However the async iterator hides that (and does automatic
cleanup).
The code lives in separate files from the rest of fs, this is done
partially to prevent over-pollution of those (already very large)
files, but also in the case of js allows loading into `fsPromises`.
Due to async_hooks, this introduces a new handle type of `DIRHANDLE`.
This PR does not attempt to make complete optimization of
this feature. Notable future improvements include:
- Moving promise work into C++ land like FileHandle.
- Possibly adding `readv()` to do multi-entry directory reads.
- Aliasing `fs.readdir` to `fs.scandir` and doing a deprecation.
Refs: https://github.com/nodejs/node-v0.x-archive/issues/388
Refs: https://github.com/nodejs/node/issues/583
Refs: https://github.com/libuv/libuv/pull/2057
PR-URL: https://github.com/nodejs/node/pull/29349
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: David Carlier <devnexen@gmail.com>
Joyee Cheung