Quota: Implement DetermineStoragePressure().

This function will allow QuotaManager to identify the state of
storage pressure when given information about disk capacity and usage.
QuotaManager will ultimately use this signal to dispatch a storage pressure event to script.

This change also moves the kStoragePressureEvent flag from content_features to quota_features so that it can be accessed from quota code, and content can never be included in storage.
This flag will remain accessible from content.

Design Doc: https://docs.google.com/document/d/1-ZzFe7ITnzW-G7uymhv_obPwfQjJwzA6wh10tfl5tCw/edit

Bug: 1088004
Change-Id: I84387f0599dde3404ffbae9014bf389bd0039ba0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2252032
Commit-Queue: Lexi Stavrakos <astavrakos@google.com>
Reviewed-by: Jarryd Goodman <jarrydg@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Darwin Huang <huangdarwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790575}

chrome/browser/about_flags.cc

@@ -164,6 +164,7 @@
 #include "services/media_session/public/cpp/features.h"
 #include "services/network/public/cpp/features.h"
 #include "services/network/public/cpp/network_switches.h"
+#include "storage/browser/quota/quota_features.h"
 #include "third_party/blink/public/common/experiments/memory_ablation_experiment.h"
 #include "third_party/blink/public/common/features.h"
 #include "third_party/blink/public/common/forcedark/forcedark_switches.h"
@@ -3995,7 +3996,7 @@ const FeatureEntry kFeatureEntries[] = {
     {"enable-storage-pressure-event",
      flag_descriptions::kStoragePressureEventName,
      flag_descriptions::kStoragePressureEventDescription, kOsAll,
-     FEATURE_VALUE_TYPE(features::kStoragePressureEvent)},
+     FEATURE_VALUE_TYPE(storage::features::kStoragePressureEvent)},
 
     {"enable-storage-pressure-ui", flag_descriptions::kStoragePressureUIName,
      flag_descriptions::kStoragePressureUIDescription, kOsAll,

content/public/common/content_features.cc

@@ -624,10 +624,6 @@ const base::Feature kSiteIsolationEnforcementForFileSystemApi{
 const base::Feature kSpareRendererForSitePerProcess{
     "SpareRendererForSitePerProcess", base::FEATURE_ENABLED_BY_DEFAULT};
 
-// Enables Storage Pressure Event.
-const base::Feature kStoragePressureEvent{"StoragePressureEvent",
-                                          base::FEATURE_DISABLED_BY_DEFAULT};
-
 // Enables Storage Pressure notifications and settings pages.
 const base::Feature kStoragePressureUI {
   "StoragePressureUI",

content/public/common/content_features.h

@@ -136,7 +136,6 @@ CONTENT_EXPORT extern const base::Feature
     kSiteIsolationEnforcementForFileSystemApi;
 CONTENT_EXPORT extern const base::Feature kSmsReceiver;
 CONTENT_EXPORT extern const base::Feature kSpareRendererForSitePerProcess;
-CONTENT_EXPORT extern const base::Feature kStoragePressureEvent;
 CONTENT_EXPORT extern const base::Feature kStoragePressureUI;
 CONTENT_EXPORT extern const base::Feature kStorageServiceOutOfProcess;
 CONTENT_EXPORT extern const base::Feature kStorageServiceSandbox;

storage/browser/quota/quota_features.cc

@@ -37,5 +37,9 @@ constexpr base::FeatureParam<double> kIncognitoQuotaRatioLowerBound{
 constexpr base::FeatureParam<double> kIncognitoQuotaRatioUpperBound{
     &kIncognitoDynamicQuota, "IncognitoQuotaRatioUpperBound", 0.2};
 
+// Enables Storage Pressure Event.
+const base::Feature kStoragePressureEvent{"StoragePressureEvent",
+                                          base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace features
 }  // namespace storage

storage/browser/quota/quota_features.h

@@ -26,6 +26,9 @@ extern const base::Feature kIncognitoDynamicQuota;
 extern const base::FeatureParam<double> kIncognitoQuotaRatioLowerBound;
 extern const base::FeatureParam<double> kIncognitoQuotaRatioUpperBound;
 
+COMPONENT_EXPORT(STORAGE_BROWSER)
+extern const base::Feature kStoragePressureEvent;
+
 }  // namespace features
 
 }  // namespace storage

storage/browser/quota/quota_manager.cc

@@ -17,11 +17,11 @@
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
-#include "base/feature_list.h"
 #include "base/files/file_util.h"
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/numerics/safe_conversions.h"
+#include "base/rand_util.h"
 #include "base/sequence_checker.h"
 #include "base/sequenced_task_runner.h"
 #include "base/single_thread_task_runner.h"
@@ -60,6 +60,12 @@ constexpr double kStoragePressureThresholdRatio = 2;
 constexpr base::TimeDelta kStoragePressureCheckDiskStatsInterval =
     base::TimeDelta::FromMinutes(5);
 
+// Modifies a given value by a uniformly random amount from
+// -percent to +percent.
+int64_t RandomizeByPercent(int64_t value, int percent) {
+  double random_percent = (base::RandDouble() - 0.5) * percent * 2;
+  return value * (1 + (random_percent / 100.0));
+}
 }  // namespace
 
 // Heuristics: assuming average cloud server allows a few Gigs storage
@@ -185,10 +191,12 @@ void DidGetUsageAndQuotaStripBreakdown(
 
 }  // namespace
 
+constexpr int64_t QuotaManager::kGBytes;
 constexpr int64_t QuotaManager::kNoLimit;
 constexpr int64_t QuotaManager::kPerHostPersistentQuotaLimit;
 constexpr int QuotaManager::kEvictionIntervalInMilliSeconds;
 constexpr int QuotaManager::kThresholdOfErrorsToBeDenylisted;
+constexpr int QuotaManager::kThresholdRandomizationPercent;
 constexpr char QuotaManager::kDatabaseName[];
 constexpr char QuotaManager::kDaysBetweenRepeatedOriginEvictionsHistogram[];
 constexpr char QuotaManager::kEvictedOriginAccessedCountHistogram[];
@@ -1485,6 +1493,25 @@ void QuotaManager::SimulateStoragePressure(const url::Origin origin) {
   storage_pressure_callback_.Run(origin);
 }
 
+void QuotaManager::DetermineStoragePressure(int64_t free_space,
+                                            int64_t total_space) {
+  if (!base::FeatureList::IsEnabled(features::kStoragePressureEvent)) {
+    return;
+  }
+  int64_t threshold_bytes =
+      RandomizeByPercent(kGBytes, kThresholdRandomizationPercent);
+  int64_t threshold = RandomizeByPercent(
+      static_cast<int64_t>(total_space *
+                           (kThresholdRandomizationPercent / 100.0)),
+      kThresholdRandomizationPercent);
+  threshold = std::min(threshold_bytes, threshold);
+
+  if (free_space < threshold) {
+    // TODO(https://crbug.com/1096549): Implement StoragePressureEvent
+    // dispatching.
+  }
+}
+
 void QuotaManager::SetStoragePressureCallback(
     base::RepeatingCallback<void(url::Origin)> storage_pressure_callback) {
   storage_pressure_callback_ = storage_pressure_callback;

storage/browser/quota/quota_manager.h

@@ -121,6 +121,7 @@ class COMPONENT_EXPORT(STORAGE_BROWSER) QuotaManager
                               int64_t quota,
                               blink::mojom::UsageBreakdownPtr usage_breakdown)>;
 
+  static constexpr int64_t kGBytes = 1024 * 1024 * 1024;
   static constexpr int64_t kNoLimit = INT64_MAX;
   static constexpr int64_t kMBytes = 1024 * 1024;
   static constexpr int kMinutesInMilliSeconds = 60 * 1000;
@@ -260,6 +261,7 @@ class COMPONENT_EXPORT(STORAGE_BROWSER) QuotaManager
   static constexpr int kEvictionIntervalInMilliSeconds =
       30 * kMinutesInMilliSeconds;
   static constexpr int kThresholdOfErrorsToBeDenylisted = 3;
+  static constexpr int kThresholdRandomizationPercent = 5;
 
   static constexpr char kDatabaseName[] = "QuotaManager";
   static constexpr char kDaysBetweenRepeatedOriginEvictionsHistogram[] =
@@ -433,6 +435,14 @@ class COMPONENT_EXPORT(STORAGE_BROWSER) QuotaManager
   // callback.
   void SimulateStoragePressure(const url::Origin origin);
 
+  // Evaluates disk statistics to identify storage pressure
+  // (low disk space availability) and starts the storage
+  // pressure event dispatch if appropriate.
+  // TODO(crbug.com/1088004): Implement UsageAndQuotaInfoGatherer::Completed()
+  // to use DetermineStoragePressure().
+  // TODO(crbug.com/1102433): Define and explain StoragePressure in the README.
+  void DetermineStoragePressure(int64_t free_space, int64_t total_space);
+
   void PostTaskAndReplyWithResultForDBThread(
       const base::Location& from_here,
       base::OnceCallback<bool(QuotaDatabase*)> task,