From 96dc1b72f3fb5d344538984121e11e5804905145 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>

Date: Wed, 13 Nov 2013 00:42:22 -0500

Subject: [PATCH] journald: do not free space when disk space runs low

Before, journald would remove journal files until both MaxUse= and

KeepFree= settings would be satisfied. The first one depends (if set

automatically) on the size of the file system and is constant.  But

the second one depends on current use of the file system, and a spike

in disk usage would cause journald to delete journal files, trying to

reach usage which would leave 15% of the disk free. This behaviour is

surprising for the user who doesn't expect his logs to be purged when

disk usage goes above 85%, which on a large disk could be some

gigabytes from being full. In addition attempting to keep 15% free

provides an attack vector where filling the disk sufficiently disposes

of almost all logs.

Instead, obey KeepFree= only as a limit on adding additional files.

When replacing old files with new, ignore KeepFree=. This means that

if journal disk usage reached some high point that at some later point

start to violate the KeepFree= constraint, journald will not add files

to go above this point, but it will stay (slightly) below it. When

journald is restarted, it forgets the previous maximum usage value,

and sets the limit based on the current usage, so if disk remains to

be filled, journald might use one journal-file-size less on each

restart, if restarts happen just after rotation. This seems like a

reasonable compromise between implementation complexity and robustness.

---

 man/journald.conf.xml                   | 39 +++++++++++++++++++++++----------

 src/journal/journal-file.h              |  1 +

 src/journal/journal-vacuum.c            |  6 ++---

 src/journal/journal-vacuum.h            |  2 +-

 src/journal/journald-server.c           | 22 ++++++++++++++-----

 src/journal/test-journal-interleaving.c |  4 ++--

 src/journal/test-journal.c              |  4 ++--

 src/shared/macro.h                      |  7 ++++++

 8 files changed, 58 insertions(+), 27 deletions(-)

diff --git a/man/journald.conf.xml b/man/journald.conf.xml

index b362c5d..e0796e1 100644

--- a/man/journald.conf.xml

+++ b/man/journald.conf.xml

@@ -250,20 +250,35 @@

                                 <para><varname>SystemMaxUse=</varname>

                                 and <varname>RuntimeMaxUse=</varname>

                                 control how much disk space the

-                                journal may use up at

-                                maximum. Defaults to 10% of the size

-                                of the respective file

-                                system. <varname>SystemKeepFree=</varname>

-                                and

+                                journal may use up at maximum.

+                                <varname>SystemKeepFree=</varname> and

                                 <varname>RuntimeKeepFree=</varname>

                                 control how much disk space

-                                systemd-journald shall always leave

-                                free for other uses. Defaults to 15%

-                                of the size of the respective file

-                                system. systemd-journald will respect

-                                both limits, i.e. use the smaller of

-                                the two values.

-                                <varname>SystemMaxFileSize=</varname>

+                                systemd-journald shall leave free for

+                                other uses.

+                                <command>systemd-journald</command>

+                                will respect both limits and use the

+                                smaller of the two values.</para>

+

+                                <para>The first pair defaults to 10%

+                                and the second to 15% of the size of

+                                the respective file system. If the

+                                file system is nearly full and either

+                                <varname>SystemKeepFree=</varname> or

+                                <varname>RuntimeKeepFree=</varname> is

+                                violated when systemd-journald is

+                                started, the value will be raised to

+                                percentage that is actually free. This

+                                means that if before there was enough

+                                free space and journal files were

+                                created, and subsequently something

+                                else causes the file system to fill

+                                up, journald will stop using more

+                                space, but it'll will not removing

+                                existing files to go reduce footprint

+                                either.</para>

+

+                                <para><varname>SystemMaxFileSize=</varname>

                                 and

                                 <varname>RuntimeMaxFileSize=</varname>

                                 control how large individual journal

diff --git a/src/journal/journal-file.h b/src/journal/journal-file.h

index 0bd23f7..2e06b57 100644

--- a/src/journal/journal-file.h

+++ b/src/journal/journal-file.h

@@ -37,6 +37,7 @@

 typedef struct JournalMetrics {

         uint64_t max_use;

+        uint64_t use;

         uint64_t max_size;

         uint64_t min_size;

         uint64_t keep_free;

diff --git a/src/journal/journal-vacuum.c b/src/journal/journal-vacuum.c

index d4a1c6c..8b07f65 100644

--- a/src/journal/journal-vacuum.c

+++ b/src/journal/journal-vacuum.c

@@ -150,7 +150,6 @@ static int journal_file_empty(int dir_fd, const char *name) {

 int journal_directory_vacuum(

                 const char *directory,

                 uint64_t max_use,

-                uint64_t min_free,

                 usec_t max_retention_usec,

                 usec_t *oldest_usec) {

@@ -164,7 +163,7 @@ int journal_directory_vacuum(

         assert(directory);

-        if (max_use <= 0 && min_free <= 0 && max_retention_usec <= 0)

+        if (max_use <= 0 && max_retention_usec <= 0)

                 return 0;

         if (max_retention_usec > 0) {

@@ -310,8 +309,7 @@ int journal_directory_vacuum(

                 }

                 if ((max_retention_usec <= 0 || list[i].realtime >= retention_limit) &&

-                    (max_use <= 0 || sum <= max_use) &&

-                    (min_free <= 0 || (uint64_t) ss.f_bavail * (uint64_t) ss.f_bsize >= min_free))

+                    (max_use <= 0 || sum <= max_use))

                         break;

                 if (unlinkat(dirfd(d), list[i].filename, 0) >= 0) {

diff --git a/src/journal/journal-vacuum.h b/src/journal/journal-vacuum.h

index f5e3e52..bc30c3a 100644

--- a/src/journal/journal-vacuum.h

+++ b/src/journal/journal-vacuum.h

@@ -23,4 +23,4 @@

 #include <inttypes.h>

-int journal_directory_vacuum(const char *directory, uint64_t max_use, uint64_t min_free, usec_t max_retention_usec, usec_t *oldest_usec);

+int journal_directory_vacuum(const char *directory, uint64_t max_use, usec_t max_retention_usec, usec_t *oldest_usec);

diff --git a/src/journal/journald-server.c b/src/journal/journald-server.c

index 1fcb3d5..cd2cfe9 100644

--- a/src/journal/journald-server.c

+++ b/src/journal/journald-server.c

@@ -158,9 +158,18 @@ static uint64_t available_space(Server *s, bool verbose) {

         }

         ss_avail = ss.f_bsize * ss.f_bavail;

-        avail = ss_avail > m->keep_free ? ss_avail - m->keep_free : 0;

-        s->cached_available_space = MIN(m->max_use, avail) > sum ? MIN(m->max_use, avail) - sum : 0;

+        /* If we reached a high mark, we will always allow this much

+         * again, unless usage goes above max_use. This watermark

+         * value is cached so that we don't give up space on pressure,

+         * but hover below the maximum usage. */

+

+        if (m->use < sum)

+                m->use = sum;

+

+        avail = LESS_BY(ss_avail, m->keep_free);

+

+        s->cached_available_space = LESS_BY(MIN(m->max_use, avail), sum);

         s->cached_available_space_timestamp = ts;

         if (verbose) {

@@ -168,13 +177,14 @@ static uint64_t available_space(Server *s, bool verbose) {

                         fb4[FORMAT_BYTES_MAX], fb5[FORMAT_BYTES_MAX];

                 server_driver_message(s, SD_MESSAGE_JOURNAL_USAGE,

-                                      "%s journal is using %s (max %s, leaving %s of free %s, current limit %s).",

+                                      "%s journal is using %s (max allowed %s, "

+                                      "trying to leave %s free of %s available → current limit %s).",

                                       s->system_journal ? "Permanent" : "Runtime",

                                       format_bytes(fb1, sizeof(fb1), sum),

                                       format_bytes(fb2, sizeof(fb2), m->max_use),

                                       format_bytes(fb3, sizeof(fb3), m->keep_free),

                                       format_bytes(fb4, sizeof(fb4), ss_avail),

-                                      format_bytes(fb5, sizeof(fb5), MIN(m->max_use, avail)));

+                                      format_bytes(fb5, sizeof(fb5), s->cached_available_space + sum));

         }

         return s->cached_available_space;

@@ -378,7 +388,7 @@ void server_vacuum(Server *s) {

         if (s->system_journal) {

                 char *p = strappenda("/var/log/journal/", ids);

-                r = journal_directory_vacuum(p, s->system_metrics.max_use, s->system_metrics.keep_free, s->max_retention_usec, &s->oldest_file_usec);

+                r = journal_directory_vacuum(p, s->system_metrics.max_use, s->max_retention_usec, &s->oldest_file_usec);

                 if (r < 0 && r != -ENOENT)

                         log_error("Failed to vacuum %s: %s", p, strerror(-r));

         }

@@ -386,7 +396,7 @@ void server_vacuum(Server *s) {

         if (s->runtime_journal) {

                 char *p = strappenda("/run/log/journal/", ids);

-                r = journal_directory_vacuum(p, s->runtime_metrics.max_use, s->runtime_metrics.keep_free, s->max_retention_usec, &s->oldest_file_usec);

+                r = journal_directory_vacuum(p, s->runtime_metrics.max_use, s->max_retention_usec, &s->oldest_file_usec);

                 if (r < 0 && r != -ENOENT)

                         log_error("Failed to vacuum %s: %s", p, strerror(-r));

         }

diff --git a/src/journal/test-journal-interleaving.c b/src/journal/test-journal-interleaving.c

index 1a058ea..974fa3b 100644

--- a/src/journal/test-journal-interleaving.c

+++ b/src/journal/test-journal-interleaving.c

@@ -194,7 +194,7 @@ static void test_skip(void (*setup)(void))

         if (arg_keep)

                 log_info("Not removing %s", t);

         else {

-                journal_directory_vacuum(".", 3000000, 0, 0, NULL);

+                journal_directory_vacuum(".", 3000000, 0, NULL);

                 assert_se(rm_rf_dangerous(t, false, true, false) >= 0);

         }

@@ -279,7 +279,7 @@ static void test_sequence_numbers(void) {

         if (arg_keep)

                 log_info("Not removing %s", t);

         else {

-                journal_directory_vacuum(".", 3000000, 0, 0, NULL);

+                journal_directory_vacuum(".", 3000000, 0, NULL);

                 assert_se(rm_rf_dangerous(t, false, true, false) >= 0);

         }

diff --git a/src/journal/test-journal.c b/src/journal/test-journal.c

index 190c426..3b8778d 100644

--- a/src/journal/test-journal.c

+++ b/src/journal/test-journal.c

@@ -126,7 +126,7 @@ static void test_non_empty(void) {

         if (arg_keep)

                 log_info("Not removing %s", t);

         else {

-                journal_directory_vacuum(".", 3000000, 0, 0, NULL);

+                journal_directory_vacuum(".", 3000000, 0, NULL);

                 assert_se(rm_rf_dangerous(t, false, true, false) >= 0);

         }

@@ -165,7 +165,7 @@ static void test_empty(void) {

         if (arg_keep)

                 log_info("Not removing %s", t);

         else {

-                journal_directory_vacuum(".", 3000000, 0, 0, NULL);

+                journal_directory_vacuum(".", 3000000, 0, NULL);

                 assert_se(rm_rf_dangerous(t, false, true, false) >= 0);

         }

diff --git a/src/shared/macro.h b/src/shared/macro.h

index d4f92b6..bc5b3c1 100644

--- a/src/shared/macro.h

+++ b/src/shared/macro.h

@@ -114,6 +114,13 @@ static inline size_t ALIGN_TO(size_t l, size_t ali) {

                         _a < _b ? _a : _b;      \

                 })

+#define LESS_BY(A,B)                            \

+        __extension__ ({                        \

+                        typeof(A) _A = (A);     \

+                        typeof(B) _B = (B);     \

+                        _A > _B ? _A - _B : 0;  \

+                })

+

 #ifndef CLAMP

 #define CLAMP(x, low, high)                                             \

         __extension__ ({                                                \