Re: infinite loop? with mmap, nfs, pwrite, O_DIRECT

[Andrew Morton]

Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote:
>
>  Anything that calls lock_page() should be avoided in O_DIRECT,

Why?

And it's still doing lock_page():

	nfs_file_direct_write()
	->filemap_fdatawrite()
	  ->do_writepages()
	    ->nfs_writepages()
	      ->generic_writepages()
	        ->mpage_writepages()
	          ->lock_page()

> however
>   we should be able to call invalidate_inode_pages() since that doesn't
>   wait on the page lock.

invalidate_inode_pages2() is better.  And using generic_file_direct_IO() is
better still, since it handles mmap coherency and only work upon that part
of the file which is actually undergoing IO.

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