[Tarantool-patches] [PATCH 12/12] popen: allow to close parent's end of std* fds
Cyrill Gorcunov
gorcunov at gmail.com
Tue Apr 14 16:05:07 MSK 2020
On Tue, Apr 14, 2020 at 02:38:21PM +0300, Alexander Turenko wrote:
> The function popen_shutdown() checks whether std{in,out,err} was piped
> and closes the parent's end. A user should have ability to send EOF for
> child's stdin for stream programs like `grep`. It is better when there
> is a function that encapsulates proper checks, error messages and the
> actual actions.
>
> This commit in particular reverts
> 1ef95b99f6553b246729e7bb5bdc19038043db74 ('popen: remove redundant fd
> check before perform IO'), because now the check is meaningful: an fd
> may become closed before the whole popen handle will be deleted.
>
> Part of #4031
> ---
> src/lib/core/popen.c | 170 ++++++++++++++++++++++++++++++++-----------
> src/lib/core/popen.h | 3 +
> 2 files changed, 130 insertions(+), 43 deletions(-)
>
> diff --git a/src/lib/core/popen.c b/src/lib/core/popen.c
> index 640dffc2b..8760429c2 100644
> --- a/src/lib/core/popen.c
> +++ b/src/lib/core/popen.c
> @@ -34,6 +34,43 @@ static RLIST_HEAD(popen_head);
> static int dev_null_fd_ro = -1;
> static int dev_null_fd_wr = -1;
>
> +static const struct {
> + unsigned int mask;
> + unsigned int mask_devnull;
> + unsigned int mask_close;
> + int fileno;
> + int *dev_null_fd;
> + int parent_idx;
> + int child_idx;
> + bool nonblock;
> +} pfd_map[POPEN_FLAG_FD_STDEND_BIT] = {
> + {
> + .mask = POPEN_FLAG_FD_STDIN,
> + .mask_devnull = POPEN_FLAG_FD_STDIN_DEVNULL,
> + .mask_close = POPEN_FLAG_FD_STDIN_CLOSE,
> + .fileno = STDIN_FILENO,
> + .dev_null_fd = &dev_null_fd_ro,
> + .parent_idx = 1,
> + .child_idx = 0,
> + }, {
> + .mask = POPEN_FLAG_FD_STDOUT,
> + .mask_devnull = POPEN_FLAG_FD_STDOUT_DEVNULL,
> + .mask_close = POPEN_FLAG_FD_STDOUT_CLOSE,
> + .fileno = STDOUT_FILENO,
> + .dev_null_fd = &dev_null_fd_wr,
> + .parent_idx = 0,
> + .child_idx = 1,
> + }, {
> + .mask = POPEN_FLAG_FD_STDERR,
> + .mask_devnull = POPEN_FLAG_FD_STDERR_DEVNULL,
> + .mask_close = POPEN_FLAG_FD_STDERR_CLOSE,
> + .fileno = STDERR_FILENO,
> + .dev_null_fd = &dev_null_fd_wr,
> + .parent_idx = 0,
> + .child_idx = 1,
> + },
> +};
> +
> /**
> * Register popen handle in a pids map.
> */
> @@ -213,7 +250,8 @@ handle_free(struct popen_handle *handle)
> * Returns 0 if so and -1 otherwise (and set a diag).
> */
> static inline int
> -popen_may_io(struct popen_handle *handle, unsigned int io_flags)
> +popen_may_io(struct popen_handle *handle, unsigned int idx,
> + unsigned int io_flags, bool allow_closed)
> {
> if (!(io_flags & handle->flags)) {
> diag_set(IllegalParams, "popen: handle does not support the "
> @@ -221,6 +259,12 @@ popen_may_io(struct popen_handle *handle, unsigned int io_flags)
> return -1;
> }
>
> + if (! allow_closed && handle->ios[idx].fd < 0) {
> + diag_set(IllegalParams, "popen: attempt to operate on a closed "
> + "file descriptor");
> + return -1;
> + }
> +
> return 0;
> }
>
> @@ -299,6 +343,7 @@ stdX_str(unsigned int index)
> * - count: data is too big.
> * - flags: POPEN_FLAG_FD_STDIN bit is unset.
> * - handle: handle does not support the requested IO operation.
> + * - handle: attempt to operate on a closed fd.
> * - SocketError: an IO error occurs at write().
> * - TimedOut: @a timeout quota is exceeded.
> * - FiberIsCancelled: cancelled by an outside code.
> @@ -327,11 +372,11 @@ popen_write_timeout(struct popen_handle *handle, const void *buf,
> return -1;
> }
>
> - if (popen_may_io(handle, flags) != 0)
> - return -1;
> -
> int idx = STDIN_FILENO;
>
> + if (popen_may_io(handle, idx, flags, false) != 0)
> + return -1;
> +
> say_debug("popen: %d: write idx [%s:%d] buf %p count %zu "
> "fds %d timeout %.9g",
> handle->pid, stdX_str(idx), idx, buf, count,
> @@ -362,6 +407,7 @@ popen_write_timeout(struct popen_handle *handle, const void *buf,
> * - count: buffer is too big.
> * - flags: stdout and stdrr are both choosen or both missed
> * - handle: handle does not support the requested IO operation.
> + * - handle: attempt to operate on a closed fd.
> * - SocketError: an IO error occurs at read().
> * - TimedOut: @a timeout quota is exceeded.
> * - FiberIsCancelled: cancelled by an outside code.
> @@ -390,12 +436,12 @@ popen_read_timeout(struct popen_handle *handle, void *buf,
> return -1;
> }
>
> - if (popen_may_io(handle, flags) != 0)
> - return -1;
> -
> int idx = flags & POPEN_FLAG_FD_STDOUT ?
> STDOUT_FILENO : STDERR_FILENO;
>
> + if (popen_may_io(handle, idx, flags, false) != 0)
> + return -1;
> +
> say_debug("popen: %d: read idx [%s:%d] buf %p count %zu "
> "fds %d timeout %.9g",
> handle->pid, stdX_str(idx), idx, buf, count,
> @@ -405,6 +451,80 @@ popen_read_timeout(struct popen_handle *handle, void *buf,
> timeout);
> }
...
> +int
> +popen_shutdown(struct popen_handle *handle, unsigned int flags)
> +{
> + assert(handle != NULL);
> +
> + if ((flags & (POPEN_FLAG_FD_STDIN |
> + POPEN_FLAG_FD_STDOUT |
> + POPEN_FLAG_FD_STDERR)) == 0) {
> + diag_set(IllegalParams,
> + "popen: neither stdin, stdout nor stderr is choosen");
> + return -1;
> + }
> +
> + /* Verify the operation. */
> + for (int idx = STDIN_FILENO; idx < POPEN_FLAG_FD_STDEND_BIT; ++idx) {
for (size_t i = 0; i < lengthof(pfd_map); i++)
We already do a build time check for STDIN_x proper mapping to numbers,
lets make it shorter.
> + /* Operate only on asked fds. */
> + unsigned int op_mask = pfd_map[idx].mask;
> + if ((flags & op_mask) == 0)
> + continue;
> +
> + if (popen_may_io(handle, idx, op_mask, true) != 0)
> + return -1;
> + }
> +
> + /* Perform the operation. */
> + for (int idx = STDIN_FILENO; idx < POPEN_FLAG_FD_STDEND_BIT; ++idx) {
> + /* Operate only on asked fds. */
> + unsigned int op_mask = pfd_map[idx].mask;
> + if ((flags & op_mask) == 0)
> + continue;
> +
> + /* Skip already closed fds. */
> + if (handle->ios[idx].fd < 0)
> + continue;
> +
> + say_debug("popen: %d: shutdown idx [%s:%d] fd %s",
> + handle->pid, stdX_str(idx), idx,
> + handle->ios[idx].fd);
> + coio_close_io(loop(), &handle->ios[idx]);
> + }
I don't get why we need two for() cycles? Also, I don't like that we
mangle popen_may_io(). The shutdown is special. Why not do something like
for (size_t idx = 0; i < lengthof(pfd_map); i++) {
unsigned int op_mask = pfd_map[idx].mask;
if ((flags & op_mask) == 0)
continue;
if (handle->ios[idx].fd < 0)
continue;
...
}
Can't we do something like that?
Cyrill
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