Fix fuse position read bug

[bzheng888]

What changes are proposed in this pull request?

The position read will return -1 when position >= filesize, then the fuse will throw an error.

/tmp/alluxio-fuse/f1 is a 1mb file.

Why are the changes needed?

Fix the fuse position read bug.

Does this PR introduce any user facing changes?

Please list the user-facing changes introduced by your change, including

1. change in user-facing APIs
2. addition or removal of property keys
3. webui

[dbw9580]

I don't think this PR fixes the described issue. Can you describe how you debugged the error?

[dbw9580]

I think the original logic is correct. We must have reached here by breaking out of the above while loop, due to currentRead < 0. If totalRead == 0, then it means the very first read call return with EOF, therefore we return currentRead here to notify the caller.

[dbw9580]

position read will return -1 when position > filesize

this is the expected behavior: you cannot read beyond the end of the file.

On the other hand, read should return 0 if position == filesize and length == 0

[bzheng888]

position read will return -1 when position > filesize

this is the expected behavior: you cannot read beyond the end of the file.

On the other hand, read should return 0 if position == filesize and length == 0

Thanks for reply, this fix may not work, but the position read problem exist any way, can you help to figure out what's going on? I did not follow up this issue in detail.

[alluxio-bot]

Automated checks report:

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[bzheng888]

The operations:

Debug info.

The read will exceed the file length actually, @dbw9580 @LuQQiu FYI

[maobaolong]

@bzheng888 I guess you may use a unknown email for this PR

[bzheng888]

@dbw9580 @LuQQiu Can you help to look this problem, thanks?

[LuQQiu]

@bzheng888 looks like the PR-EMAIL failed? Email not linked to a valid Github account

[LuQQiu]

@bzheng888 can you help create a github issue and link to this PR?

[LuQQiu]

alluxio-bot, merge this please

[alluxio-bot]

merge failed:
Merge refused because pull request does not have label start with type-

[LuQQiu]

alluxio-bot, merge this please

[bzheng888]

@bzheng888 can you help create a github issue and link to this PR?

Ok