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Date: Mon, 19 Feb 2007 18:11:55 +0100 From: Miklos Szeredi <miklos@...redi.hu> To: akpm@...ux-foundation.org CC: linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: dirty balancing deadlock How about this? Solves the FUSE deadlock, but not the throttle_vm_writeout() one. I'll try to tackle that one as well. If the per-bdi dirty counter goes below 16, balance_dirty_pages() returns. Does the constant need to tunable? If it's too large, then the global threshold is more easily exceeded. If it's too small, then in a tight situation progress will be slower. Thanks, Miklos Index: linux/mm/page-writeback.c =================================================================== --- linux.orig/mm/page-writeback.c 2007-02-19 17:32:41.000000000 +0100 +++ linux/mm/page-writeback.c 2007-02-19 18:05:28.000000000 +0100 @@ -198,6 +198,25 @@ static void balance_dirty_pages(struct a dirty_thresh) break; + /* + * Acquit this producer if there's little or nothing + * to write back to this particular queue + * + * Without this check a deadlock is possible in the + * following case: + * + * - filesystem A writes data through filesystem B + * - filesystem A has dirty pages over dirty_thresh + * - writeback is started, this triggers a write in B + * - balance_dirty_pages() is called synchronously + * - the write to B blocks + * - the writeback completes, but dirty is still over threshold + * - the blocking write prevents futher writes from happening + */ + if (atomic_long_read(&bdi->nr_dirty) + + atomic_long_read(&bdi->nr_writeback) < 16) + break; + if (!dirty_exceeded) dirty_exceeded = 1; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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