core: make settings for unified cgroup hierarchy supersede the ones for legacy hierarchy (#4269)

There are overlapping control group resource settings for the unified and
legacy hierarchies.  To help transition, the settings are translated back and
forth.  When both versions of a given setting are present, the one matching the
cgroup hierarchy type in use is used.  Unfortunately, this is more confusing to
use and document than necessary because there is no clear static precedence.

Update the translation logic so that the settings for the unified hierarchy are
always preferred.  elogind.resource-control man page is updated to reflect the
change and reorganized so that the deprecated settings are at the end in its
own section.

1 files changed, 29 insertions, 31 deletions

diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index ccdab64a6..9e4e99326 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -688,16 +688,16 @@ static void cgroup_context_apply(Unit *u, CGroupMask mask, ManagerState state) {
                 } else {
                         uint64_t shares;
 
-                        if (has_shares)
-                                shares = cgroup_context_cpu_shares(c, state);
-                        else if (has_weight) {
+                        if (has_weight) {
                                 uint64_t weight = cgroup_context_cpu_weight(c, state);
 
                                 shares = cgroup_cpu_weight_to_shares(weight);
 
                                 log_cgroup_compat(u, "Applying [Startup]CpuWeight %" PRIu64 " as [Startup]CpuShares %" PRIu64 " on %s",
                                                   weight, shares, path);
-                        } else
+                        } else if (has_shares)
+                                shares = cgroup_context_cpu_shares(c, state);
+                        else
                                 shares = CGROUP_CPU_SHARES_DEFAULT;
 
                         cgroup_apply_legacy_cpu_config(u, shares, c->cpu_quota_per_sec_usec);
@@ -789,16 +789,16 @@ static void cgroup_context_apply(Unit *u, CGroupMask mask, ManagerState state) {
                         char buf[DECIMAL_STR_MAX(uint64_t)+1];
                         uint64_t weight;
 
-                        if (has_blockio)
-                                weight = cgroup_context_blkio_weight(c, state);
-                        else if (has_io) {
+                        if (has_io) {
                                 uint64_t io_weight = cgroup_context_io_weight(c, state);
 
                                 weight = cgroup_weight_io_to_blkio(cgroup_context_io_weight(c, state));
 
                                 log_cgroup_compat(u, "Applying [Startup]IOWeight %" PRIu64 " as [Startup]BlockIOWeight %" PRIu64,
                                                   io_weight, weight);
-                        } else
+                        } else if (has_blockio)
+                                weight = cgroup_context_blkio_weight(c, state);
+                        else
                                 weight = CGROUP_BLKIO_WEIGHT_DEFAULT;
 
                         xsprintf(buf, "%" PRIu64 "\n", weight);
@@ -807,13 +807,7 @@ static void cgroup_context_apply(Unit *u, CGroupMask mask, ManagerState state) {
                                 log_unit_full(u, IN_SET(r, -ENOENT, -EROFS, -EACCES) ? LOG_DEBUG : LOG_WARNING, r,
                                               "Failed to set blkio.weight: %m");
 
-                        if (has_blockio) {
-                                CGroupBlockIODeviceWeight *w;
-
-                                /* FIXME: no way to reset this list */
-                                LIST_FOREACH(device_weights, w, c->blockio_device_weights)
-                                        cgroup_apply_blkio_device_weight(u, w->path, w->weight);
-                        } else if (has_io) {
+                        if (has_io) {
                                 CGroupIODeviceWeight *w;
 
                                 /* FIXME: no way to reset this list */
@@ -825,18 +819,17 @@ static void cgroup_context_apply(Unit *u, CGroupMask mask, ManagerState state) {
 
                                         cgroup_apply_blkio_device_weight(u, w->path, weight);
                                 }
+                        } else if (has_blockio) {
+                                CGroupBlockIODeviceWeight *w;
+
+                                /* FIXME: no way to reset this list */
+                                LIST_FOREACH(device_weights, w, c->blockio_device_weights)
+                                        cgroup_apply_blkio_device_weight(u, w->path, w->weight);
                         }
                 }
 
                 /* Apply limits and free ones without config. */
-                if (has_blockio) {
-                        CGroupBlockIODeviceBandwidth *b, *next;
-
-                        LIST_FOREACH_SAFE(device_bandwidths, b, next, c->blockio_device_bandwidths) {
-                                if (!cgroup_apply_blkio_device_limit(u, b->path, b->rbps, b->wbps))
-                                        cgroup_context_free_blockio_device_bandwidth(c, b);
-                        }
-                } else if (has_io) {
+                if (has_io) {
                         CGroupIODeviceLimit *l, *next;
 
                         LIST_FOREACH_SAFE(device_limits, l, next, c->io_device_limits) {
@@ -846,13 +839,19 @@ static void cgroup_context_apply(Unit *u, CGroupMask mask, ManagerState state) {
                                 if (!cgroup_apply_blkio_device_limit(u, l->path, l->limits[CGROUP_IO_RBPS_MAX], l->limits[CGROUP_IO_WBPS_MAX]))
                                         cgroup_context_free_io_device_limit(c, l);
                         }
+                } else if (has_blockio) {
+                        CGroupBlockIODeviceBandwidth *b, *next;
+
+                        LIST_FOREACH_SAFE(device_bandwidths, b, next, c->blockio_device_bandwidths)
+                                if (!cgroup_apply_blkio_device_limit(u, b->path, b->rbps, b->wbps))
+                                        cgroup_context_free_blockio_device_bandwidth(c, b);
                 }
         }
 
         if ((mask & CGROUP_MASK_MEMORY) && !is_root) {
                 if (cg_all_unified() > 0) {
-                        uint64_t max = c->memory_max;
-                        uint64_t swap_max = c->memory_swap_max;
+                        uint64_t max;
+                        uint64_t swap_max = CGROUP_LIMIT_MAX;
 
                         if (cgroup_context_has_unified_memory_config(c)) {
                                 max = c->memory_max;
@@ -870,14 +869,13 @@ static void cgroup_context_apply(Unit *u, CGroupMask mask, ManagerState state) {
                         cgroup_apply_unified_memory_limit(u, "memory.swap.max", swap_max);
                 } else {
                         char buf[DECIMAL_STR_MAX(uint64_t) + 1];
-                        uint64_t val = c->memory_limit;
+                        uint64_t val;
 
-                        if (val == CGROUP_LIMIT_MAX) {
+                        if (cgroup_context_has_unified_memory_config(c)) {
                                 val = c->memory_max;
-
-                                if (val != CGROUP_LIMIT_MAX)
-                                        log_cgroup_compat(u, "Applying MemoryMax %" PRIi64 " as MemoryLimit", c->memory_max);
-                        }
+                                log_cgroup_compat(u, "Applying MemoryMax %" PRIi64 " as MemoryLimit", val);
+                        } else
+                                val = c->memory_limit;
 
                         if (val == CGROUP_LIMIT_MAX)
                                 strncpy(buf, "-1\n", sizeof(buf));