From 2c905207db37c691d4abef868165ad5ea2dd0f4f Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Mon, 25 May 2020 00:37:26 +0200 Subject: core: improve log messages when we cannot process a mount point Whenever we pick up a new line in /proc/self/mountinfo and want to synthesize a new mount unit from it, let's say which one it is. Moreover, downgrade the log message when we encounter a mount point with an overly long name to LOG_WARNING, since it's generally fine to ignore such mount points. Also, attach a catalog entry to explain the situation further. Prompted-By: #15221 --- catalog/systemd.catalog.in | 31 +++++++++++++++++++++++++++++++ src/core/mount.c | 27 ++++++++++++++++++++++++--- src/systemd/sd-messages.h | 5 +++++ 3 files changed, 60 insertions(+), 3 deletions(-) diff --git a/catalog/systemd.catalog.in b/catalog/systemd.catalog.in index 3342d59422..b29ba6d65b 100644 --- a/catalog/systemd.catalog.in +++ b/catalog/systemd.catalog.in @@ -435,3 +435,34 @@ hyphen and otherwise fully numeric. For further details on strict and relaxed user/group name rules, see: https://systemd.io/USER_NAMES + +-- 1b3bb94037f04bbf81028e135a12d293 +Subject: Failed to generate valid unit name from path '@MOUNT_POINT@'. +Defined-By: systemd +Support: %SUPPORT_URL% + +The following mount point path could not be converted into a valid .mount +unit name: + + @MOUNT_POINT@ + +Typically this means that the path to the mount point is longer than allowed +for valid unit names. + +systemd dynamically synthesizes .mount units for all mount points appearing on +the system. For that a simple escaping algorithm is applied: the absolute path +name is used, with all "/" characters replaced by "-" (the leading one is +removed). Moreover, any non-alphanumeric characters (as well as any of ":", +"-", "_", ".", "\") are replaced by "\xNN" where "NN" is the hexadecimal code +of the character. Finally, ".mount" is suffixed. The resulting string must be +under 256 characters in length to be a valid unit name. This restriction is +made in order for all unit names to also be suitable as file names. If a mount +point appears that — after escaping — is longer than this limit it cannot be +mapped to a unit. In this case systemd will refrain from synthesizing a unit +and cannot be used to manage the mount point. It will not appear in the service +manager's unit table and thus also not be torn down safely and automatically at +system shutdown. + +It is generally recommended to avoid such overly long mount point paths, or — +if used anyway – manage them independently of systemd, i.e. establish them as +well as tear them down automatically at system shutdown by other software. diff --git a/src/core/mount.c b/src/core/mount.c index 48500b4932..86a6098332 100644 --- a/src/core/mount.c +++ b/src/core/mount.c @@ -1672,9 +1672,30 @@ static int mount_setup_unit( if (!is_path(where)) return 0; + /* Mount unit names have to be (like all other unit names) short enough to fit into file names. This + * means there's a good chance that overly long mount point paths after mangling them to look like a + * unit name would result in unit names we don't actually consider valid. This should be OK however + * as such long mount point paths should not happen on regular systems — and if they appear + * nonetheless they are generally synthesized by software, and thus managed by that other + * software. Having such long names just means you cannot use systemd to manage those specific mount + * points, which should be an OK restriction to make. After all we don't have to be able to manage + * all mount points in the world — as long as we don't choke on them when we encounter them. */ r = unit_name_from_path(where, ".mount", &e); - if (r < 0) - return log_error_errno(r, "Failed to generate unit name from path '%s': %m", where); + if (r < 0) { + static RateLimit rate_limit = { /* Let's log about this at warning level at most once every + * 5s. Given that we generate this whenever we read the file + * otherwise we probably shouldn't flood the logs with + * this */ + .interval = 5 * USEC_PER_SEC, + .burst = 1, + }; + + return log_struct_errno( + ratelimit_below(&rate_limit) ? LOG_WARNING : LOG_DEBUG, r, + "MESSAGE_ID=" SD_MESSAGE_MOUNT_POINT_PATH_NOT_SUITABLE_STR, + "MOUNT_POINT=%s", where, + LOG_MESSAGE("Failed to generate valid unit name from path '%s', ignoring mount point: %m", where)); + } u = manager_get_unit(m, e); if (u) @@ -1684,7 +1705,7 @@ static int mount_setup_unit( * by the sysadmin having called mount(8) directly. */ r = mount_setup_new_unit(m, e, what, where, options, fstype, &flags, &u); if (r < 0) - return log_warning_errno(r, "Failed to set up mount unit: %m"); + return log_warning_errno(r, "Failed to set up mount unit for '%s': %m", where); /* If the mount changed properties or state, let's notify our clients */ if (flags & (MOUNT_PROC_JUST_CHANGED|MOUNT_PROC_JUST_MOUNTED)) diff --git a/src/systemd/sd-messages.h b/src/systemd/sd-messages.h index 162b650e64..f5dd0a04c7 100644 --- a/src/systemd/sd-messages.h +++ b/src/systemd/sd-messages.h @@ -161,6 +161,11 @@ _SD_BEGIN_DECLARATIONS; #define SD_MESSAGE_UNSAFE_USER_NAME SD_ID128_MAKE(b6,1f,da,c6,12,e9,4b,91,82,28,5b,99,88,43,06,1f) #define SD_MESSAGE_UNSAFE_USER_NAME_STR SD_ID128_MAKE_STR(b6,1f,da,c6,12,e9,4b,91,82,28,5b,99,88,43,06,1f) +#define SD_MESSAGE_MOUNT_POINT_PATH_NOT_SUITABLE \ + SD_ID128_MAKE(1b,3b,b9,40,37,f0,4b,bf,81,02,8e,13,5a,12,d2,93) +#define SD_MESSAGE_MOUNT_POINT_PATH_NOT_SUITABLE_STR \ + SD_ID128_MAKE_STR(1b,3b,b9,40,37,f0,4b,bf,81,02,8e,13,5a,12,d2,93) + _SD_END_DECLARATIONS; #endif -- cgit v1.2.1