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Lunev" , Eric Blake , Vladimir Sementsov-Ogievskiy , Hanna Reitz , Michael Tokarev Subject: [Stable-7.2.5 05/14] qemu-nbd: fix regression with qemu-nbd --fork run over ssh Date: Tue, 25 Jul 2023 17:09:59 +0300 Message-Id: <20230725141009.3372529-5-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: "Denis V. Lunev" Commit e6df58a5578fee7a50bbf36f4a50a2781cff855d Author: Hanna Reitz Date: Wed May 8 23:18:18 2019 +0200 qemu-nbd: Do not close stderr has introduced an interesting regression. Original behavior of ssh somehost qemu-nbd /home/den/tmp/file -f raw --fork was the following: * qemu-nbd was started as a daemon * the command execution is done and ssh exited with success The patch has changed this behavior and 'ssh' command now hangs forever. According to the normal specification of the daemon() call, we should endup with STDERR pointing to /dev/null. That should be done at the very end of the successful startup sequence when the pipe to the bootstrap process (used for diagnostics) is no longer needed. This could be achived in the same way as done for 'qemu-nbd -c' case. That was commit 0eaf453e, also fixing up e6df58a5. STDOUT copying to STDERR does the trick. This also leads to proper 'ssh' connection closing which fixes my original problem. Signed-off-by: Denis V. Lunev CC: Eric Blake CC: Vladimir Sementsov-Ogievskiy CC: Hanna Reitz CC: Message-ID: <20230717145544.194786-3-den@openvz.org> Reviewed-by: Eric Blake Signed-off-by: Eric Blake (cherry picked from commit 5c56dd27a2c905c9cf2472d2fd057621ce5fd00d) Signed-off-by: Michael Tokarev diff --git a/qemu-nbd.c b/qemu-nbd.c index 89afd2e749..bcdb74ff13 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -274,6 +274,7 @@ static void *show_parts(void *arg) struct NbdClientOpts { char *device; + bool fork_process; }; static void *nbd_client_thread(void *arg) @@ -317,7 +318,7 @@ static void *nbd_client_thread(void *arg) /* update partition table */ pthread_create(&show_parts_thread, NULL, show_parts, opts->device); - if (verbose) { + if (verbose && !opts->fork_process) { fprintf(stderr, "NBD device %s is now connected to %s\n", opts->device, srcpath); } else { @@ -579,7 +580,6 @@ int main(int argc, char **argv) bool writethrough = false; /* Client will flush as needed. */ bool fork_process = false; bool list = false; - int old_stderr = -1; unsigned socket_activation; const char *pid_file_name = NULL; const char *selinux_label = NULL; @@ -934,11 +934,6 @@ int main(int argc, char **argv) } else if (pid == 0) { close(stderr_fd[0]); - /* Remember parent's stderr if we will be restoring it. */ - if (fork_process) { - old_stderr = dup(STDERR_FILENO); - } - ret = qemu_daemon(1, 0); /* Temporarily redirect stderr to the parent's pipe... */ @@ -1129,6 +1124,7 @@ int main(int argc, char **argv) int ret; struct NbdClientOpts opts = { .device = device, + .fork_process = fork_process, }; ret = pthread_create(&client_thread, NULL, nbd_client_thread, &opts); @@ -1157,8 +1153,7 @@ int main(int argc, char **argv) } if (fork_process) { - dup2(old_stderr, STDERR_FILENO); - close(old_stderr); + dup2(STDOUT_FILENO, STDERR_FILENO); } state = RUNNING;