Messages in this thread | | | Date | Mon, 19 Feb 2007 19:16:20 -0500 | From | Chris Mason <> | Subject | Re: dirty balancing deadlock |
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On Mon, Feb 19, 2007 at 02:14:15AM +0100, Miklos Szeredi wrote: > > > > In general, writepage is supposed to do work without blocking on > > > > expensive locks that will get pdflush and dirty reclaim stuck in this > > > > fashion. You'll probably have to take the same approach reiserfs does > > > > in data=journal mode, which is leaving the page dirty if fuse_get_req_wp > > > > is going to block without making progress. > > > > > > Pdflush, and dirty reclaim set wbc->nonblocking to true. > > > balance_dirty_pages and fsync don't. The problem here is that > > > Andrew's patch is wrong to let balance_dirty_pages() try to write back > > > pages from a different queue. > > > > async or sync, writepage is supposed to either make progress or bail. > > loopback aside, if the fuse call is blocking long term, you're going to > > run into problems. > > Hmm, like what?
Something a little different from what you're seeing. Basically if the PF_MEMALLOC paths end up waiting on a filesystem transaction, and that transaction is waiting for more ram, the system will eventually grind to a halt. data=journal is the easiest way to hit it, since writepage always logs at least 4k.
WB_SYNC_NONE and wbc->nonblocking aren't a great test, in reiser I resorted to testing PF_MEMALLOC.
-chris
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