repart: Rework Minimize= option settings

Instead of having Minimize= take a boolean let's allow for two
different ways to enable it. "best" means we want the most minimal
image possible, which currently is only possible for read-only
filesystems but can be extended in the future with bisection
to find the most minimal possible size.

We also add "guess", which is the current behavior, where we
populate once and use the sparse size to make a reasonable guess
on a size that fits all the sources without needing to O(log(n))
tries to find the most minimal size.

1 files changed, 24 insertions, 4 deletions

diff --git a/src/partition/repart.c b/src/partition/repart.c
index b70c54e531..80cd7daba3 100644
--- a/src/partition/repart.c
+++ b/src/partition/repart.c
@@ -178,6 +178,14 @@ typedef enum VerityMode {
         _VERITY_MODE_INVALID = -EINVAL,
 } VerityMode;
 
+typedef enum MinimizeMode {
+        MINIMIZE_OFF,
+        MINIMIZE_BEST,
+        MINIMIZE_GUESS,
+        _MINIMIZE_MODE_MAX,
+        _MINIMIZE_MODE_INVALID = -EINVAL,
+} MinimizeMode;
+
 typedef struct Partition {
         char *definition_path;
         char **drop_in_files;
@@ -221,7 +229,7 @@ typedef struct Partition {
         EncryptMode encrypt;
         VerityMode verity;
         char *verity_match_key;
-        bool minimize;
+        MinimizeMode minimize;
 
         uint64_t gpt_flags;
         int no_auto;
@@ -284,8 +292,15 @@ static const char *verity_mode_table[_VERITY_MODE_MAX] = {
         [VERITY_SIG]  = "signature",
 };
 
+static const char *minimize_mode_table[_MINIMIZE_MODE_MAX] = {
+        [MINIMIZE_OFF]   = "off",
+        [MINIMIZE_BEST]  = "best",
+        [MINIMIZE_GUESS] = "guess",
+};
+
 DEFINE_PRIVATE_STRING_TABLE_LOOKUP_FROM_STRING_WITH_BOOLEAN(encrypt_mode, EncryptMode, ENCRYPT_KEY_FILE);
 DEFINE_PRIVATE_STRING_TABLE_LOOKUP(verity_mode, VerityMode);
+DEFINE_PRIVATE_STRING_TABLE_LOOKUP_FROM_STRING_WITH_BOOLEAN(minimize_mode, MinimizeMode, MINIMIZE_BEST);
 
 static uint64_t round_down_size(uint64_t v, uint64_t p) {
         return (v / p) * p;
@@ -1532,6 +1547,7 @@ static int config_parse_uuid(
 }
 
 static DEFINE_CONFIG_PARSE_ENUM_WITH_DEFAULT(config_parse_verity, verity_mode, VerityMode, VERITY_OFF, "Invalid verity mode");
+static DEFINE_CONFIG_PARSE_ENUM_WITH_DEFAULT(config_parse_minimize, minimize_mode, MinimizeMode, MINIMIZE_OFF, "Invalid minimize mode");
 
 static int partition_read_definition(Partition *p, const char *path, const char *const *conf_file_dirs) {
 
@@ -1559,7 +1575,7 @@ static int partition_read_definition(Partition *p, const char *path, const char
                 { "Partition", "NoAuto",          config_parse_tristate,    0, &p->no_auto           },
                 { "Partition", "GrowFileSystem",  config_parse_tristate,    0, &p->growfs            },
                 { "Partition", "SplitName",       config_parse_string,      0, &p->split_name_format },
-                { "Partition", "Minimize",        config_parse_bool,        0, &p->minimize          },
+                { "Partition", "Minimize",        config_parse_minimize,    0, &p->minimize          },
                 {}
         };
         int r;
@@ -1616,10 +1632,14 @@ static int partition_read_definition(Partition *p, const char *path, const char
                         return log_oom();
         }
 
-        if (p->minimize && !p->format)
+        if (p->minimize != MINIMIZE_OFF && !p->format)
                 return log_syntax(NULL, LOG_ERR, path, 1, SYNTHETIC_ERRNO(EINVAL),
                                   "Minimize= can only be enabled if Format= is set");
 
+        if (p->minimize == MINIMIZE_BEST && !fstype_is_ro(p->format))
+                return log_syntax(NULL, LOG_ERR, path, 1, SYNTHETIC_ERRNO(EINVAL),
+                                  "Minimize=best can only be used with read-only filesystems");
+
         if ((!strv_isempty(p->copy_files) || !strv_isempty(p->make_directories)) && !mkfs_supports_root_option(p->format) && geteuid() != 0)
                 return log_syntax(NULL, LOG_ERR, path, 1, SYNTHETIC_ERRNO(EPERM),
                                   "Need to be root to populate %s filesystems with CopyFiles=/MakeDirectories=",
@@ -5282,7 +5302,7 @@ static int context_minimize(Context *context) {
                 if (!p->format)
                         continue;
 
-                if (!p->minimize)
+                if (p->minimize == MINIMIZE_OFF)
                         continue;
 
                 if (!partition_needs_populate(p))