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([2a01:e0a:999:a3a0:45f5:4d94:4aa8:def4]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-422f61277fesm187080885e9.21.2024.06.18.04.17.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Jun 2024 04:17:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20230601.gappssmtp.com; s=20230601; t=1718709471; x=1719314271; darn=nongnu.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=0v7uteVDRSl1sGyj9u/oI9Vuada/Ql0A0kiqrgdJeqs=; b=mnspmBi0Anu1zFxbNwIKdtstLiaX9N4zne5PM69Jd4LXMjjvViYYUZwjbjqcac3C0A X7hStAG+iCNWXgBf3UISIoQHomoXnj6R+y9zgmliGlk3+TJgtmJ3dEwEX2hSAus8U2po x6q8zBWX4PUX/ClfN7OVIFsQEu8iK0ol1dSWnx5KJBL1dsGVN9JCxZBSVFcy0JWmxf6o KCszksEXc8bOLwbh045bkFOgMfkkUPCe0cumMPNWOuwt7nQLppY702BAcBQ02X8YJlId 6FxGYIHWRUCHCrb9iESb7E9Zob1phRAD9tHq496j+j40zS8dlHwfdh1uF2MaVFwqe3b+ hetQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718709471; x=1719314271; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=0v7uteVDRSl1sGyj9u/oI9Vuada/Ql0A0kiqrgdJeqs=; b=AoEtosz7emIVh+1OCph8IhUodgsZgcM7n9/lktEGJbuLJMnxugrt+5EE7iodzMaYbN /n905e/6vwv7Bsx8qFGOYRh6/Ldb4XcC+B7r5sVVp7O1hHlm0hkUFww4Nkqh93/94G5W D+5x3eGQwAReklfPF4nFQipsAbGyDXGXw57abOvAtttsenFf+LuknZ1Bi9Bng/uMrZKP pv3VGeGg/ttcght5UOVusH3b4dzJXyPRtBjuwCNsHMF5kX9RowRlHrVKS1579eEkJPVi eGDJ/gJG8V5MDUI1Pj9J+drwCII4ci0FqLQRjLeCVcaTZZlwCVhrcO34G3uE233p9L68 hRjg== X-Gm-Message-State: AOJu0Yz1Xjtg38J7zPW+Hdi3HiKJFvOI2dMmYVRGY78F3RiH3poJdy81 3MqlFA2qetpem3pS4rKDazMXyEo9OqU/4UmZrrBB7t+CRAibJe4SrL0jfgEY0DECvMT1oakp9pY 1MIM= X-Google-Smtp-Source: AGHT+IHJhzfdRXObyvyABps8k3QmuRbwQEV7jTQFTwOaYg7gf4pd38aGjCmqdbUWA8lV9haNh9Aejw== X-Received: by 2002:a05:651c:1a1e:b0:2ea:8442:2096 with SMTP id 38308e7fff4ca-2ec0e47f142mr76313541fa.2.1718709470899; Tue, 18 Jun 2024 04:17:50 -0700 (PDT) From: =?UTF-8?q?Cl=C3=A9ment=20L=C3=A9ger?= To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Cl=C3=A9ment=20L=C3=A9ger?= , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Peter Maydell , Jason Wang Subject: [PATCH v2] osdep: add a qemu_close_all_open_fd() helper Date: Tue, 18 Jun 2024 13:17:03 +0200 Message-ID: <20240618111704.63092-1-cleger@rivosinc.com> X-Mailer: git-send-email 2.45.2 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::232; envelope-from=cleger@rivosinc.com; helo=mail-lj1-x232.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @rivosinc-com.20230601.gappssmtp.com) X-ZM-MESSAGEID: 1718709513077100001 Since commit 03e471c41d8b ("qemu_init: increase NOFILE soft limit on POSIX"), the maximum number of file descriptors that can be opened are raised to nofile.rlim_max. On recent debian distro, this yield a maximum of 1073741816 file descriptors. Now, when forking to start qemu-bridge-helper, this actually calls close() on the full possible file descriptor range (more precisely [3 - sysconf(_SC_OPEN_MAX)]) which takes a considerable amount of time. In order to reduce that time, factorize existing code to close all open files descriptors in a new qemu_close_all_open_fd() function. This function uses various methods to close all the open file descriptors ranging from the most efficient one to the least one. It also accepts an ordered array of file descriptors that should not be closed since this is required by the callers that calls it after forking. Signed-off-by: Cl=C3=A9ment L=C3=A9ger ---- v2: - Factorize async_teardown.c close_fds implementation as well as tap.c ones - Apply checkpatch - v1: https://lore.kernel.org/qemu-devel/20240617162520.4045016-1-cleger@r= ivosinc.com/ --- include/qemu/osdep.h | 8 +++ net/tap.c | 31 ++++++----- system/async-teardown.c | 37 +------------ util/osdep.c | 115 ++++++++++++++++++++++++++++++++++++++++ 4 files changed, 141 insertions(+), 50 deletions(-) diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index f61edcfdc2..9369a97d3d 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -755,6 +755,14 @@ static inline void qemu_reset_optind(void) =20 int qemu_fdatasync(int fd); =20 +/** + * Close all open file descriptors except the ones supplied in the @skip a= rray + * + * @skip: ordered array of distinct file descriptors that should not be cl= osed + * @nskip: number of entries in the @skip array. + */ +void qemu_close_all_open_fd(const int *skip, unsigned int nskip); + /** * Sync changes made to the memory mapped file back to the backing * storage. For POSIX compliant systems this will fallback diff --git a/net/tap.c b/net/tap.c index 51f7aec39d..6fc3939078 100644 --- a/net/tap.c +++ b/net/tap.c @@ -385,6 +385,21 @@ static TAPState *net_tap_fd_init(NetClientState *peer, return s; } =20 +static void close_all_fds_after_fork(int excluded_fd) +{ + const int skip_fd[] =3D {0, 1, 2, 3, excluded_fd}; + unsigned int nskip =3D ARRAY_SIZE(skip_fd); + + /* + * skip_fd must be an ordered array of distinct fds, exclude + * excluded_fd if already included in the [0 - 3] range + */ + if (excluded_fd <=3D 3) { + nskip--; + } + qemu_close_all_open_fd(skip_fd, nskip); +} + static void launch_script(const char *setup_script, const char *ifname, int fd, Error **errp) { @@ -400,13 +415,7 @@ static void launch_script(const char *setup_script, co= nst char *ifname, return; } if (pid =3D=3D 0) { - int open_max =3D sysconf(_SC_OPEN_MAX), i; - - for (i =3D 3; i < open_max; i++) { - if (i !=3D fd) { - close(i); - } - } + close_all_fds_after_fork(fd); parg =3D args; *parg++ =3D (char *)setup_script; *parg++ =3D (char *)ifname; @@ -490,17 +499,11 @@ static int net_bridge_run_helper(const char *helper, = const char *bridge, return -1; } if (pid =3D=3D 0) { - int open_max =3D sysconf(_SC_OPEN_MAX), i; char *fd_buf =3D NULL; char *br_buf =3D NULL; char *helper_cmd =3D NULL; =20 - for (i =3D 3; i < open_max; i++) { - if (i !=3D sv[1]) { - close(i); - } - } - + close_all_fds_after_fork(sv[1]); fd_buf =3D g_strdup_printf("%s%d", "--fd=3D", sv[1]); =20 if (strrchr(helper, ' ') || strrchr(helper, '\t')) { diff --git a/system/async-teardown.c b/system/async-teardown.c index 396963c091..9148ee8d04 100644 --- a/system/async-teardown.c +++ b/system/async-teardown.c @@ -26,40 +26,6 @@ =20 static pid_t the_ppid; =20 -/* - * Close all open file descriptors. - */ -static void close_all_open_fd(void) -{ - struct dirent *de; - int fd, dfd; - DIR *dir; - -#ifdef CONFIG_CLOSE_RANGE - int r =3D close_range(0, ~0U, 0); - if (!r) { - /* Success, no need to try other ways. */ - return; - } -#endif - - dir =3D opendir("/proc/self/fd"); - if (!dir) { - /* If /proc is not mounted, there is nothing that can be done. */ - return; - } - /* Avoid closing the directory. */ - dfd =3D dirfd(dir); - - for (de =3D readdir(dir); de; de =3D readdir(dir)) { - fd =3D atoi(de->d_name); - if (fd !=3D dfd) { - close(fd); - } - } - closedir(dir); -} - static void hup_handler(int signal) { /* Check every second if this process has been reparented. */ @@ -85,9 +51,8 @@ static int async_teardown_fn(void *arg) /* * Close all file descriptors that might have been inherited from the * main qemu process when doing clone, needed to make libvirt happy. - * Not using close_range for increased compatibility with older kernel= s. */ - close_all_open_fd(); + qemu_close_all_open_fd(NULL, 0); =20 /* Set up a handler for SIGHUP and unblock SIGHUP. */ sigaction(SIGHUP, &sa, NULL); diff --git a/util/osdep.c b/util/osdep.c index 5d23bbfbec..f3710710e3 100644 --- a/util/osdep.c +++ b/util/osdep.c @@ -625,3 +625,118 @@ int qemu_fdatasync(int fd) return fsync(fd); #endif } + +#ifdef CONFIG_LINUX +static bool qemu_close_all_open_fd_proc(const int *skip, unsigned int nski= p) +{ + struct dirent *de; + int fd, dfd; + bool close_fd; + DIR *dir; + int i; + + dir =3D opendir("/proc/self/fd"); + if (!dir) { + /* If /proc is not mounted, there is nothing that can be done. */ + return false; + } + /* Avoid closing the directory. */ + dfd =3D dirfd(dir); + + for (de =3D readdir(dir); de; de =3D readdir(dir)) { + fd =3D atoi(de->d_name); + close_fd =3D true; + if (fd =3D=3D dfd) { + close_fd =3D false; + } else { + for (i =3D 0; i < nskip; i++) { + if (fd =3D=3D skip[i]) { + close_fd =3D false; + break; + } + } + } + if (close_fd) { + close(fd); + } + } + closedir(dir); + + return true; +} +#else +static bool qemu_close_all_open_fd_proc(const int *skip, unsigned int nski= p) +{ + return false; +} +#endif + +#ifdef CONFIG_CLOSE_RANGE +static bool qemu_close_all_open_fd_close_range(const int *skip, + unsigned int nskip) +{ + int max_fd =3D sysconf(_SC_OPEN_MAX) - 1; + int first =3D 0, last =3D max_fd; + int cur_skip =3D 0, ret; + + do { + if (nskip) { + while (first =3D=3D skip[cur_skip]) { + cur_skip++; + first++; + } + if (cur_skip < nskip) { + last =3D skip[cur_skip] - 1; + } + if (last > max_fd) { + last =3D max_fd; + /* + * We can directly skip the remaining skip fds since the c= urrent + * one is already above the maximum supported one. + */ + cur_skip =3D nskip; + } + if (first > last) { + break; + } + } + ret =3D close_range(first, last, 0); + if (ret < 0) { + return false; + } + first =3D last + 1; + last =3D max_fd; + } while (cur_skip < nskip); + + return true; +} +#else +static bool qemu_close_all_open_fd_close_range(const int *skip, + unsigned int nskip) +{ + return false; +} +#endif + +void qemu_close_all_open_fd(const int *skip, unsigned int nskip) +{ + int open_max =3D sysconf(_SC_OPEN_MAX); + int cur_skip =3D 0, i; + + if (qemu_close_all_open_fd_close_range(skip, nskip)) { + return; + } + + if (qemu_close_all_open_fd_proc(skip, nskip)) { + return; + } + + /* Fallback */ + for (i =3D 0; i < open_max; i++) { + if (i =3D=3D skip[cur_skip]) { + cur_skip++; + continue; + } + close(i); + } +} --=20 2.45.2