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https://issues.apache.org/jira/browse/HDFS-10982?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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John Zhuge reassigned HDFS-10982:
---------------------------------
Assignee: John Zhuge
> 'errno' set on successful code path in hdfsOpenFileImpl()
> ---------------------------------------------------------
>
> Key: HDFS-10982
> URL: https://issues.apache.org/jira/browse/HDFS-10982
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: libhdfs
> Affects Versions: 2.7.0
> Reporter: Sailesh Mukil
> Assignee: John Zhuge
> Labels: easyfix
>
> In hdfsOpenFileImpl() in libhdfs/hdfs.c, the following code is used to check
> if the underlying FileSystem class supports direct reads (i.e.
> read(ByteBuffer)):
> {code:java}
> if ((flags & O_WRONLY) == 0) {
> // Try a test read to see if we can do direct reads
> char buf;
> if (readDirect(fs, file, &buf, 0) == 0) {
> // Success - 0-byte read should return 0
> file->flags |= HDFS_FILE_SUPPORTS_DIRECT_READ;
> } else if (errno != ENOTSUP) {
> // Unexpected error. Clear it, don't set the direct flag.
> fprintf(stderr,
> "hdfsOpenFile(%s): WARN: Unexpected error %d when testing "
> "for direct read compatibility\n", path, errno);
> }
> }
> ret = 0;
> {code}
> The S3A connector, specifically S3AInputStream does not support direct reads,
> and therefore it sets 'errno = ENOTSUP' on a call to readDirect().
> This 'errno' should be reset before returning the call because this is not an
> actual error and we're okay with not having direct reads supported.
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