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Date: Sat, 17 Mar 2012 17:21:48 +0100 From: Dmitry Adamushko <dmitry.adamushko@...il.com> To: John Stultz <john.stultz@...aro.org> Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Android Kernel Team <kernel-team@...roid.com>, Robert Love <rlove@...gle.com>, Mel Gorman <mel@....ul.ie>, Hugh Dickins <hughd@...gle.com>, Dave Hansen <dave@...ux.vnet.ibm.com>, Rik van Riel <riel@...hat.com>, Dave Chinner <david@...morbit.com>, Neil Brown <neilb@...e.de>, Andrea Righi <andrea@...terlinux.com>, "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> Subject: Re: [PATCH 2/2] [RFC] fadvise: Add _VOLATILE,_ISVOLATILE, and _NONVOLATILE flags Hi John, [ ... ] > +/* > + * Mark a region as volatile, allowing dirty pages to be purged > + * under memory pressure > + */ > +long mapping_range_volatile(struct address_space *mapping, > + pgoff_t start_index, pgoff_t end_index) > +{ > + struct volatile_range *new; > + struct range_tree_node *node; > + > + u64 start, end; > + int purged = 0; > + start = (u64)start_index; > + end = (u64)end_index; > + > + new = vrange_alloc(); > + if (!new) > + return -ENOMEM; > + > + mutex_lock(&volatile_mutex); > + > + node = range_tree_in_range_adjacent(&mapping->volatile_root, > + start, end); > + while (node) { > + struct volatile_range *vrange; > + > + /* Already entirely marked volatile, so we're done */ > + if (node->start < start && node->end > end) { > + /* don't need the allocated value */ > + kfree(new); > + goto out; > + } > + > + /* Grab containing volatile range */ > + vrange = container_of(node, struct volatile_range, range_node); > + > + /* resize range */ > + start = min_t(u64, start, node->start); > + end = max_t(u64, end, node->end); > + purged |= vrange->purged; > + > + > + vrange_del(vrange); > + > + /* get the next possible overlap */ > + node = range_tree_in_range(&mapping->volatile_root, start, end); I guess range_tree_in_range_adjacent() should be used here again. There can be 2 adjacent regions (left and right), and we'll miss one of them with range_tree_in_range(). Also (as I had already mentioned before), I think that new ranges must not be merged with the existing "vrange->purged == 1" ranges. Otherwise, for some use cases, the whole idea of 'volatility' gets broken. For example, when an application is processing a big buffer in small consequent chunks (marking a chunk as volatile when done with it), and the range gets 'purged' by the kernel early in this process (when it's still small). -- Dmitry -- 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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