On Thu, 2008-08-07 at 12:15 +0900, Hisashi Hifumi wrote:

quoted

/*
* This is like invalidate_complete_page(), except it ignores the page's
* refcount.  We do this because invalidate_inode_pages2() needs
stronger
* invalidation guarantees, and cannot afford to leave pages behind
because
* shrink_page_list() has a temp ref on them, or because they're
transiently
* sitting in the lru_cache_add() pagevecs.
*/


I am wondering why we need stronger invalidate hurantees for DIO->
invalidate_inode_pages_range(),which force the page being removed from
page cache? In case of bh is busy due to ext3 writeout,
journal_try_to_free_buffers() could return different error number(EBUSY)
to try_to_releasepage() (instead of EIO).  In that case,  could we just
leave the page in the cache, clean pageuptodate() (to force later buffer
read to read from disk) and then invalidate_complete_page2() return
successfully? Any issue with this way?

My idea is that journal_try_to_free_buffers returns EBUSY if it fails due to
bh busy, and dio write falls back to buffered write. This is easy to fix.

What about the invalidates done after the DIO has already run
non-buffered?

-chris