xz: Use non-blocking I/O for the input file.
diff --git a/src/xz/file_io.c b/src/xz/file_io.c
index 6598ef6..fd22dc4 100644
--- a/src/xz/file_io.c
+++ b/src/xz/file_io.c
@@ -17,6 +17,7 @@
#ifdef TUKLIB_DOSLIKE
# include <io.h>
#else
+# include <poll.h>
static bool warn_fchown;
#endif
@@ -41,6 +42,11 @@
static bool try_sparse = true;
#ifndef TUKLIB_DOSLIKE
+/// File status flags of standard input. This is used by io_open_src()
+/// and io_close_src().
+static int stdin_flags;
+static bool restore_stdin_flags = false;
+
/// Original file status flags of standard output. This is used by
/// io_open_dest() and io_close_dest() to save and restore the flags.
static int stdout_flags;
@@ -84,6 +90,47 @@
}
+#ifndef TUKLIB_DOSLIKE
+/// \brief Waits for input or output to become available
+static bool
+io_wait(file_pair *pair, bool is_reading)
+{
+ struct pollfd pfd[1];
+
+ if (is_reading) {
+ pfd[0].fd = pair->src_fd;
+ pfd[0].events = POLLIN;
+ } else {
+ pfd[0].fd = pair->dest_fd;
+ pfd[0].events = POLLOUT;
+ }
+
+ while (true) {
+ const int ret = poll(pfd, 1, -1);
+
+ if (ret == -1) {
+ if (errno == EINTR) {
+ if (user_abort)
+ return true;
+
+ continue;
+ }
+
+ if (errno == EAGAIN)
+ continue;
+
+ message_error(_("%s: poll() failed: %s"),
+ is_reading ? pair->src_name
+ : pair->dest_name,
+ strerror(errno));
+ }
+
+ return false;
+ }
+}
+#endif
+
+
/// \brief Unlink a file
///
/// This tries to verify that the file being unlinked really is the file that
@@ -293,6 +340,27 @@
pair->src_fd = STDIN_FILENO;
#ifdef TUKLIB_DOSLIKE
setmode(STDIN_FILENO, O_BINARY);
+#else
+ // Enable O_NONBLOCK for stdin.
+ stdin_flags = fcntl(STDIN_FILENO, F_GETFL);
+ if (stdin_flags == -1) {
+ message_error(_("Error getting the file status flags "
+ "from standard input: %s"),
+ strerror(errno));
+ return true;
+ }
+
+ if ((stdin_flags & O_NONBLOCK) == 0) {
+ if (fcntl(STDIN_FILENO, F_SETFL,
+ stdin_flags | O_NONBLOCK) == -1) {
+ message_error(_("Error setting O_NONBLOCK "
+ "on standard input: %s"),
+ strerror(errno));
+ return true;
+ }
+
+ restore_stdin_flags = true;
+ }
#endif
#ifdef HAVE_POSIX_FADVISE
// It will fail if stdin is a pipe and that's fine.
@@ -314,13 +382,12 @@
int flags = O_RDONLY | O_BINARY | O_NOCTTY;
#ifndef TUKLIB_DOSLIKE
- // If we accept only regular files, we need to be careful to avoid
- // problems with special files like devices and FIFOs. O_NONBLOCK
- // prevents blocking when opening such files. When we want to accept
- // special files, we must not use O_NONBLOCK, or otherwise we won't
- // block waiting e.g. FIFOs to become readable.
- if (reg_files_only)
- flags |= O_NONBLOCK;
+ // Use non-blocking I/O:
+ // - It prevents blocking when opening FIFOs and some other
+ // special files, which is good if we want to accept only
+ // regular files.
+ // - It can help avoiding some race conditions with signal handling.
+ flags |= O_NONBLOCK;
#endif
#if defined(O_NOFOLLOW)
@@ -348,30 +415,13 @@
(void)follow_symlinks;
#endif
- // Try to open the file. If we are accepting non-regular files,
- // unblock the caught signals so that open() can be interrupted
- // if it blocks e.g. due to a FIFO file.
- if (!reg_files_only)
- signals_unblock();
-
- // Maybe this wouldn't need a loop, since all the signal handlers for
- // which we don't use SA_RESTART set user_abort to true. But it
- // doesn't hurt to have it just in case.
- do {
- pair->src_fd = open(pair->src_name, flags);
- } while (pair->src_fd == -1 && errno == EINTR && !user_abort);
-
- if (!reg_files_only)
- signals_block();
+ // Try to open the file. Signals have been blocked so EINTR shouldn't
+ // be possible.
+ pair->src_fd = open(pair->src_name, flags);
if (pair->src_fd == -1) {
- // If we were interrupted, don't display any error message.
- if (errno == EINTR) {
- // All the signals that don't have SA_RESTART
- // set user_abort.
- assert(user_abort);
- return true;
- }
+ // Signals (that have a signal handler) have been blocked.
+ assert(errno != EINTR);
#ifdef O_NOFOLLOW
// Give an understandable error message if the reason
@@ -430,22 +480,6 @@
return true;
}
-#ifndef TUKLIB_DOSLIKE
- // Drop O_NONBLOCK, which is used only when we are accepting only
- // regular files. After the open() call, we want things to block
- // instead of giving EAGAIN.
- if (reg_files_only) {
- flags = fcntl(pair->src_fd, F_GETFL);
- if (flags == -1)
- goto error_msg;
-
- flags &= ~O_NONBLOCK;
-
- if (fcntl(pair->src_fd, F_SETFL, flags) == -1)
- goto error_msg;
- }
-#endif
-
// Stat the source file. We need the result also when we copy
// the permissions, and when unlinking.
//
@@ -505,6 +539,18 @@
goto error;
}
}
+
+ // If it is something else than a regular file, wait until
+ // there is input available. This way reading from FIFOs
+ // will work when open() is used with O_NONBLOCK.
+ if (!S_ISREG(pair->src_st.st_mode)) {
+ signals_unblock();
+ const bool ret = io_wait(pair, true);
+ signals_block();
+
+ if (ret)
+ goto error;
+ }
#endif
#ifdef HAVE_POSIX_FADVISE
@@ -560,6 +606,17 @@
static void
io_close_src(file_pair *pair, bool success)
{
+ if (restore_stdin_flags) {
+ assert(pair->src_fd == STDIN_FILENO);
+
+ restore_stdin_flags = false;
+
+ if (fcntl(STDIN_FILENO, F_SETFL, stdin_flags) == -1)
+ message_error(_("Error restoring the status flags "
+ "to standard input: %s"),
+ strerror(errno));
+ }
+
if (pair->src_fd != STDIN_FILENO && pair->src_fd != -1) {
#ifdef TUKLIB_DOSLIKE
(void)close(pair->src_fd);
@@ -872,6 +929,15 @@
continue;
}
+#ifndef TUKLIB_DOSLIKE
+ if (errno == EAGAIN || errno == EWOULDBLOCK) {
+ if (!io_wait(pair, true))
+ continue;
+
+ return SIZE_MAX;
+ }
+#endif
+
message_error(_("%s: Read error: %s"),
pair->src_name, strerror(errno));
