Re: PATCH: Rewrite of truncate_inode_pages (WIP)

[Trond Myklebust <trond.myklebust@fys.uio.no>]

>>>>> " " == Juan J Quintela <quintela@fi.udc.es> writes:

     > This patch does:

     > - defines a new function: discard_buffer, it will lock the buffer
     >   (waiting if needed) and remove the buffer from all the
     >   queues.  It is like unmap_buffer, but makes sure that we
     >   don't do any IO and that we remove the buffer from all the
     >   lists.

     > - defines a new function: block_destroy_buffers: it is a mix of
     >   block_flushpage and do_try_to_free_pages.  It will make all
     >   the buffers in that page disappear calling discard_buffer.
     >   Notice the way that we iterate through all the buffer heads.
     >   I think that it is not racy, but I would like to hear
     >   comments from people than know more about buffer heads
     >   handling.

     > - I change invalidate_inode_pages (again).  Now block_destroy_buffers
     >   can wait, then we are *civilized* citizens and drop any lock
     >   that we have before call that block_destroy_buffers, and
     >   reaquire later.

This is a bug! invalidate_inode_pages() is not supposed to invalidate
pending writes. It is only supposed to invalidate the page cache.

Also, it is pointless to add block device-specific code to that
particular function since no block devices actually use it.

Cheers,
  Trond
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