samueldlightfoot commented on code in PR #4178:
URL: https://github.com/apache/cassandra/pull/4178#discussion_r2758160436
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src/java/org/apache/cassandra/io/util/FileUtils.java:
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@@ -740,14 +741,54 @@ public static void deleteDirectoryIfEmpty(Path path)
throws IOException
}
}
+ public static boolean isDirectIOSupported(File file)
+ {
+ File testFile = null;
+ try
+ {
+ File dir = file.isDirectory() ? file : file.parent();
+ testFile = createTempFile("direct-io-test", ".tmp", dir);
+
+ // Direct IO requires knowing the block size for buffer alignment
+ if (blockSize(testFile) <= 0)
+ return false;
+
+ try (FileChannel channel = FileChannel.open(testFile.toPath(),
Review Comment:
The try-with resources pattern used here will close the channel immediately
after opening.
https://manpages.ubuntu.com/manpages/xenial//man2/open.2.html
> O_DIRECT support was added under Linux in kernel version 2.4.10.
Older Linux kernels simply ignore this
> flag. Some filesystems may not implement the flag and open() will
fail with EINVAL if it is used.
The blockSize check is not wrong, but it alone does not guarantee Direct I/O
is supported by the underlying filesystem.
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