Messages in this thread |  | | Date | Thu, 05 Sep 2002 14:12:23 -0700 | From | Andrew Morton <> | Subject | Re: invalidate_inode_pages in 2.5.32/3 |
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Trond Myklebust wrote: > > >>>>> " " == Andrew Morton <akpm@zip.com.au> writes: > > > Probably, it worked OK with the global locking because nobody > > was taking a temp ref against those pages. > > But we still have global locking in that readdir by means of the > BKL. There should be no nasty races... > > > Please tell me exactly what semantics NFS needs in there. Does > > truncate_inode_pages() do the wrong thing? > > Definitely. In most cases we *cannot* wait on I/O completion because > nfs_zap_caches() can be called directly from the 'rpciod' process by > means of a callback. Since 'rpciod' is responsible for completing all > asynchronous I/O, then truncate_inode_pages() would deadlock.
But if there are such pages, invalidate_inode_pages() would not have removed them anyway?
> As I said: I don't believe the problem here has anything to do with > invalidate_inode_pages vs. truncate_inode_pages: > - Pages should only be locked if they are actually being read from > the server. > - They should only be refcounted and/or cleared while the BKL is > held... > There is no reason why code which worked fine under 2.2.x and 2.4.x > shouldn't work under 2.5.x.
Trond, there are very good reasons why it broke. Those pages are visible to the whole world via global data structures - both the page LRUs and via the superblocks->inodes walk. Those things exist for legitimate purposes, and it is legitimate for async threads of control to take a reference on those pages while playing with them.
It just "happened to work" in earlier kernels.
I suspect we can just remove the page_count() test from invalidate and that will fix everything up. That will give stronger invalidate and anything which doesn't like that is probably buggy wrt truncate anyway.
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