CASSANDRA-21511: Fix page cache eviction for ranges larger than 2 GiB

src/java/org/apache/cassandra/utils/NativeLibrary.java

@@ -226,16 +226,27 @@ public static void trySkipCache(String path, long offset, long len)
     }
 
     public static void trySkipCache(int fd, long offset, long len, String path)
+    {
+        trySkipCache(offset, len, (subOffset, subLength) -> trySkipCache(fd, subOffset, subLength, path));
+    }
+
+    @FunctionalInterface
+    interface SkipCache
+    {
+        void skip(long offset, int len);
+    }
+
+    static void trySkipCache(long offset, long len, SkipCache skipCache)
     {
         if (len == 0)
-            trySkipCache(fd, 0, 0, path);
+            skipCache.skip(0, 0);
 
         while (len > 0)
         {
             int sublen = (int) Math.min(Integer.MAX_VALUE, len);
-            trySkipCache(fd, offset, sublen, path);
+            skipCache.skip(offset, sublen);
             len -= sublen;
-            offset -= sublen;
+            offset += sublen;
         }
     }
 

test/unit/org/apache/cassandra/utils/NativeLibraryTest.java

@@ -18,6 +18,8 @@
  */
 package org.apache.cassandra.utils;
 
+import java.util.ArrayList;
+import java.util.List;
 
 import org.junit.Assert;
 import org.junit.Test;
@@ -41,4 +43,48 @@ public void getPid()
         long pid = NativeLibrary.getProcessID();
         Assert.assertTrue(pid > 0);
     }
+
+    @Test
+    public void testSkipCacheSplitsLargeRangeAtIncreasingOffsets()
+    {
+        long offset = 1024;
+        long length = 2L * Integer.MAX_VALUE + 1;
+        List<long[]> ranges = new ArrayList<>();
+
+        NativeLibrary.trySkipCache(offset, length, (subOffset, subLength) -> ranges.add(new long[]{ subOffset, subLength }));
+
+        Assert.assertEquals(3, ranges.size());
+        assertRange(ranges.get(0), offset, Integer.MAX_VALUE);
+        assertRange(ranges.get(1), offset + Integer.MAX_VALUE, Integer.MAX_VALUE);
+        assertRange(ranges.get(2), offset + 2L * Integer.MAX_VALUE, 1);
+    }
+
+    @Test
+    public void testSkipCacheDoesNotSplitMaximumIntegerRange()
+    {
+        long offset = 4096;
+        List<long[]> ranges = new ArrayList<>();
+
+        NativeLibrary.trySkipCache(offset, Integer.MAX_VALUE, (subOffset, subLength) -> ranges.add(new long[]{ subOffset, subLength }));
+
+        Assert.assertEquals(1, ranges.size());
+        assertRange(ranges.get(0), offset, Integer.MAX_VALUE);
+    }
+
+    @Test
+    public void testSkipCacheZeroLengthTargetsEntireFile()
+    {
+        List<long[]> ranges = new ArrayList<>();
+
+        NativeLibrary.trySkipCache(4096, 0, (subOffset, subLength) -> ranges.add(new long[]{ subOffset, subLength }));
+
+        Assert.assertEquals(1, ranges.size());
+        assertRange(ranges.get(0), 0, 0);
+    }
+
+    private static void assertRange(long[] range, long offset, int length)
+    {
+        Assert.assertEquals(offset, range[0]);
+        Assert.assertEquals(length, range[1]);
+    }
 }