Re: [patch 1/2] mm: dont clear PG_uptodate in invalidate_complete_page2()

On Wed, 25 Jun 2008, Miklos Szeredi wrote:

We discussed this yesterday.  My conclusion was (which I still think
is true) that it can't be fixed in page_cache_pipe_buf_confirm(),
because due to current practice of not setting PG_error for I/O errors
for read, it is impossible to distinguish between a never-been-uptodate
page and a was-uptodate-before-invalidation page.

Umm. The regular read does this quite well. If something isn't up-to-date, 
it tries a synchronous read. Once.

And it's not just an nfsd issue.  Userspace might also expect that if
a zero count is returned, that means it went beyond EOF, and not that
it should retry the splice, maybe it has better luck this time.

You're totally ignoring the real issue - user space that uses splice() 
*knows* that it uses splice(). It's a private mmap(). 

NFSD, on the other hand, is supposed to act as NFSD. I think that 
currently it assumes that nobody else modifies the files, which is 
reasonable, but breaks with FUSE.

But do you see? That's a NFSD/FUSE issue, not a splice one!

		Linus

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