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Date: Tue, 4 Oct 2016 15:28:05 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: CAI Qian <caiqian@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
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Subject: Re: [RFC][CFT] splice_read reworked
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On Tue, Oct 04, 2016 at 09:29:35AM -0400, CAI Qian wrote:

> > Is there any way to record the sequence of syscalls leading to that?
> > 
> Yes, a bit long shot though.
> 
> http://people.redhat.com/qcai/tmp/trinity-child113.log

;-/

Not enough information, unfortunately (descriptor in question opened
outside of that log, sendfile(out_fd=578, in_fd=578, offset=0x7f8318a07000,
count=0x3ffc00) doesn't tell what *offset was before the call) ;-/

Anyway, I've found and fixed a bug in pipe_advance(), which might or might
not help with those.  Could you try vfs.git#work.splice_read (or #for-next)
and see if these persist?