From 9c68b5675ffd11f2a3f9123446b54c2d0eea4682 Mon Sep 17 00:00:00 2001

From: Yu Watanabe <watanabe.yu+github@gmail.com>

Date: Wed, 1 Sep 2021 04:16:21 +0900

Subject: [PATCH] udev-node: save information about device node and priority in

 symlink

Previously, we only store device IDs in /run/udev/links, and when

creating/removing device node symlink, we create sd_device object

corresponds to the IDs and read device node and priority from the

object. That requires parsing uevent and udev database files.

This makes link_find_prioritized() get the most prioritzed device node

without parsing the files.

(cherry picked from commit 377a83f0d80376456d9be203796f66f543a8b943)

Related: #1977994

---

 src/udev/udev-node.c | 172 ++++++++++++++++++++++++++++++-------------

 1 file changed, 121 insertions(+), 51 deletions(-)

diff --git a/src/udev/udev-node.c b/src/udev/udev-node.c

index 4496a2bd9b..5d6aae0bd4 100644

--- a/src/udev/udev-node.c

+++ b/src/udev/udev-node.c

@@ -18,6 +18,7 @@

 #include "fs-util.h"

 #include "hexdecoct.h"

 #include "mkdir.h"

+#include "parse-util.h"

 #include "path-util.h"

 #include "selinux-util.h"

 #include "smack-util.h"

@@ -28,9 +29,9 @@

 #include "udev-node.h"

 #include "user-util.h"

-#define CREATE_LINK_MAX_RETRIES 128

-#define LINK_UPDATE_MAX_RETRIES 128

-#define TOUCH_FILE_MAX_RETRIES  128

+#define CREATE_LINK_MAX_RETRIES        128

+#define LINK_UPDATE_MAX_RETRIES        128

+#define CREATE_STACK_LINK_MAX_RETRIES  128

 #define UDEV_NODE_HASH_KEY SD_ID128_MAKE(b9,6a,f1,ce,40,31,44,1a,9e,19,ec,8b,ae,f3,e3,2f)

 static int create_symlink(const char *target, const char *slink) {

@@ -175,39 +176,67 @@ static int link_find_prioritized(sd_device *dev, bool add, const char *stackdir,

                 return r;

         FOREACH_DIRENT_ALL(dent, dir, break) {

-                _cleanup_(sd_device_unrefp) sd_device *dev_db = NULL;

-                const char *devnode;

-                int db_prio = 0;

+                _cleanup_free_ char *path = NULL, *buf = NULL;

+                int tmp_prio;

-                if (dent->d_name[0] == '\0')

-                        break;

                 if (dent->d_name[0] == '.')

                         continue;

-                log_device_debug(dev, "Found '%s' claiming '%s'", dent->d_name, stackdir);

-

-                /* did we find ourself? */

+                /* skip ourself */

                 if (streq(dent->d_name, id))

                         continue;

-                if (sd_device_new_from_device_id(&dev_db, dent->d_name) < 0)

-                        continue;

+                path = path_join(stackdir, dent->d_name);

+                if (!path)

+                        return -ENOMEM;

-                if (sd_device_get_devname(dev_db, &devnode) < 0)

-                        continue;

+                if (readlink_malloc(path, &buf) >= 0) {

+                        char *devnode;

-                if (device_get_devlink_priority(dev_db, &db_prio) < 0)

-                        continue;

+                        /* New format. The devnode and priority can be obtained from symlink. */

-                if (target && db_prio <= priority)

-                        continue;

+                        devnode = strchr(buf, ':');

+                        if (!devnode || devnode == buf)

+                                continue;

-                log_device_debug(dev_db, "Device claims priority %i for '%s'", db_prio, stackdir);

+                        *(devnode++) = '\0';

+                        if (!path_startswith(devnode, "/dev"))

+                                continue;

-                r = free_and_strdup(&target, devnode);

-                if (r < 0)

-                        return r;

-                priority = db_prio;

+                        if (safe_atoi(buf, &tmp_prio) < 0)

+                                continue;

+

+                        if (target && tmp_prio <= priority)

+                                continue;

+

+                        r = free_and_strdup(&target, devnode);

+                        if (r < 0)

+                                return r;

+                } else {

+                        _cleanup_(sd_device_unrefp) sd_device *tmp_dev = NULL;

+                        const char *devnode;

+

+                        /* Old format. The devnode and priority must be obtained from uevent and

+                         * udev database files. */

+

+                        if (sd_device_new_from_device_id(&tmp_dev, dent->d_name) < 0)

+                                continue;

+

+                        if (device_get_devlink_priority(tmp_dev, &tmp_prio) < 0)

+                                continue;

+

+                        if (target && tmp_prio <= priority)

+                                continue;

+

+                        if (sd_device_get_devname(tmp_dev, &devnode) < 0)

+                                continue;

+

+                        r = free_and_strdup(&target, devnode);

+                        if (r < 0)

+                                return r;

+                }

+

+                priority = tmp_prio;

         }

         *ret = TAKE_PTR(target);

@@ -256,10 +285,72 @@ toolong:

         return size - 1;

 }

+static int update_stack_directory(sd_device *dev, const char *dirname, bool add) {

+        _cleanup_free_ char *filename = NULL, *data = NULL, *buf = NULL;

+        const char *devname, *id;

+        int priority, r;

+

+        assert(dev);

+        assert(dirname);

+

+        r = device_get_device_id(dev, &id;;

+        if (r < 0)

+                return log_device_debug_errno(dev, r, "Failed to get device id: %m");

+

+        filename = path_join(dirname, id);

+        if (!filename)

+                return log_oom_debug();

+

+        if (!add) {

+                if (unlink(filename) < 0 && errno != ENOENT)

+                        log_device_debug_errno(dev, errno, "Failed to remove %s, ignoring: %m", filename);

+

+                (void) rmdir(dirname);

+                return 0;

+        }

+

+        r = sd_device_get_devname(dev, &devname);

+        if (r < 0)

+                return log_device_debug_errno(dev, r, "Failed to get device node: %m");

+

+        r = device_get_devlink_priority(dev, &priority);

+        if (r < 0)

+                return log_device_debug_errno(dev, r, "Failed to get priority of device node symlink: %m");

+

+        if (asprintf(&data, "%i:%s", priority, devname) < 0)

+                return log_oom_debug();

+

+        if (readlink_malloc(filename, &buf) >= 0 && streq(buf, data))

+                return 0;

+

+        if (unlink(filename) < 0 && errno != ENOENT)

+                log_device_debug_errno(dev, errno, "Failed to remove %s, ignoring: %m", filename);

+

+        for (unsigned j = 0; j < CREATE_STACK_LINK_MAX_RETRIES; j++) {

+                /* This may fail with -ENOENT when the parent directory is removed during

+                 * creating the file by another udevd worker. */

+                r = mkdir_p(dirname, 0755);

+                if (r == -ENOENT)

+                        continue;

+                if (r < 0)

+                        return log_device_debug_errno(dev, r, "Failed to create directory %s: %m", dirname);

+

+                if (symlink(data, filename) < 0) {

+                        if (errno == ENOENT)

+                                continue;

+                        return log_device_debug_errno(dev, errno, "Failed to create symbolic link %s: %m", filename);

+                }

+

+                return 0;

+        }

+

+        return log_device_debug_errno(dev, SYNTHETIC_ERRNO(ELOOP), "Failed to create symbolic link %s: %m", filename);

+}

+

 /* manage "stack of names" with possibly specified device priorities */

 static int link_update(sd_device *dev, const char *slink_in, bool add) {

-        _cleanup_free_ char *slink = NULL, *filename = NULL, *dirname = NULL;

-        const char *slink_name, *id;

+        _cleanup_free_ char *slink = NULL, *dirname = NULL;

+        const char *slink_name;

         char name_enc[NAME_MAX+1];

         int i, r, retries;

@@ -279,35 +370,14 @@ static int link_update(sd_device *dev, const char *slink_in, bool add) {

                 return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL),

                                               "Invalid symbolic link of device node: %s", slink);

-        r = device_get_device_id(dev, &id;;

-        if (r < 0)

-                return log_device_debug_errno(dev, r, "Failed to get device id: %m");

-

         (void) udev_node_escape_path(slink_name, name_enc, sizeof(name_enc));

-        dirname = path_join("/run/udev/links/", name_enc);

+        dirname = path_join("/run/udev/links", name_enc);

         if (!dirname)

                 return log_oom_debug();

-        filename = path_join(dirname, id);

-        if (!filename)

-                return log_oom_debug();

-

-        if (!add) {

-                if (unlink(filename) < 0 && errno != ENOENT)

-                        log_device_debug_errno(dev, errno, "Failed to remove %s, ignoring: %m", filename);

-

-                (void) rmdir(dirname);

-        } else {

-                for (unsigned j = 0; j < TOUCH_FILE_MAX_RETRIES; j++) {

-                        /* This may fail with -ENOENT when the parent directory is removed during

-                         * creating the file by another udevd worker. */

-                        r = touch_file(filename, /* parents= */ true, USEC_INFINITY, UID_INVALID, GID_INVALID, 0444);

-                        if (r != -ENOENT)

-                                break;

-                }

-                if (r < 0)

-                        return log_device_debug_errno(dev, r, "Failed to create %s: %m", filename);

-        }

+        r = update_stack_directory(dev, dirname, add);

+        if (r < 0)

+                return r;

         /* If the database entry is not written yet we will just do one iteration and possibly wrong symlink

          * will be fixed in the second invocation. */