From mboxrd@z Thu Jan  1 00:00:00 1970
From: hujianyang <hujianyang@huawei.com>
Subject: Cursor in readdir
Date: Sat, 29 Nov 2014 18:11:40 +0800
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To: Miklos Szeredi <miklos@szeredi.hu>
Cc: linux-unionfs@vger.kernel.org

Hi Miklos,

Sorry for disturb you. I'm confused with *cursor* in struct
ovl_dir_file. I know this struct ovl_cache_entry *cursor* is
presented to indicate current pos when performing readdir at
a MERGE type directory.

Why this additional entry is needed? Can't we use a pointer
to record which entry is read or is ready for reading? After
finish reading lower and upper directories, entries in struct
ovl_dir_cache is stabilized. Changing of directories will
cause the later .readdir() to create a new ovl_dir_cache but
the old cache will not be released until all the holders of
it call .release().

So I think a pointer points to an entry in the entry list of
ovl_dir_cache is enough to each process sharing the access
of the same cache. We don't need to keep and move an special
entry, *cursor*. That's my thought.

I've considered a lot and googled some key words but found
nothing. Did I miss something important?

It will be fine if you'd like to explain the requirement of
*cursor* in readdir. Thanks a lot~!


Hu