From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 166356B005A for ; Wed, 12 Aug 2009 10:57:25 -0400 (EDT) Received: from elvis.elte.hu ([157.181.1.14]) by mx3.mail.elte.hu with esmtp (Exim) id 1MbFGd-0004x7-FO from for ; Wed, 12 Aug 2009 16:57:31 +0200 Resent-Message-ID: <20090812145728.GA29882@elte.hu> Resent-To: linux-mm@kvack.org From: Nitin Gupta Reply-To: ngupta@vflare.org Date: Wed, 12 Aug 2009 20:07:43 +0530 MIME-Version: 1.0 Content-Disposition: inline Subject: [PATCH] swap: send callback when swap slot is freed Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Message-Id: <200908122007.43522.ngupta@vflare.org> Sender: owner-linux-mm@kvack.org To: mingo@elte.hu Cc: linux-kernel@vger.kernel.org List-ID: Currently, we have "swap discard" mechanism which sends a discard bio request when we find a free cluster during scan_swap_map(). This callback can come a long time after swap slots are actually freed. This delay in callback is a great problem when (compressed) RAM [1] is used as a swap device. So, this change adds a callback which is called as soon as a swap slot becomes free. For above mentioned case of swapping over compressed RAM device, this is very useful since we can immediately free memory allocated for this swap page. This callback does not replace swap discard support. It is called with swap_lock held, so it is meant to trigger action that finishes quickly. However, swap discard is an I/O request and can be used for taking longer actions. Links: [1] http://code.google.com/p/compcache/ Signed-off-by: Nitin Gupta --- include/linux/swap.h | 5 +++++ mm/swapfile.c | 16 ++++++++++++++++ 2 files changed, 21 insertions(+), 0 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 7c15334..4cbe3c4 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -8,6 +8,7 @@ #include #include #include +#include #include #include @@ -20,6 +21,8 @@ struct bio; #define SWAP_FLAG_PRIO_MASK 0x7fff #define SWAP_FLAG_PRIO_SHIFT 0 +typedef void (swap_free_notify_fn) (struct block_device *, unsigned long); + static inline int current_is_kswapd(void) { return current->flags & PF_KSWAPD; @@ -155,6 +158,7 @@ struct swap_info_struct { unsigned int max; unsigned int inuse_pages; unsigned int old_block_size; + swap_free_notify_fn *swap_free_notify_fn; }; struct swap_list_t { @@ -295,6 +299,7 @@ extern sector_t swapdev_block(int, pgoff_t); extern struct swap_info_struct *get_swap_info_struct(unsigned); extern int reuse_swap_page(struct page *); extern int try_to_free_swap(struct page *); +extern void set_swap_free_notify(unsigned, swap_free_notify_fn *); struct backing_dev_info; /* linux/mm/thrash.c */ diff --git a/mm/swapfile.c b/mm/swapfile.c index 8ffdc0d..aa95fc7 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -552,6 +552,20 @@ out: return NULL; } +/* + * Sets callback for event when swap_map[offset] == 0 + * i.e. page at this swap offset is no longer used. + */ +void set_swap_free_notify(unsigned type, swap_free_notify_fn *notify_fn) +{ + struct swap_info_struct *sis; + sis = get_swap_info_struct(type); + BUG_ON(!sis); + sis->swap_free_notify_fn = notify_fn; + return; +} +EXPORT_SYMBOL(set_swap_free_notify); + static int swap_entry_free(struct swap_info_struct *p, swp_entry_t ent, int cache) { @@ -583,6 +597,8 @@ static int swap_entry_free(struct swap_info_struct *p, swap_list.next = p - swap_info; nr_swap_pages++; p->inuse_pages--; + if (p->swap_free_notify_fn) + p->swap_free_notify_fn(p->bdev, offset); } if (!swap_count(count)) mem_cgroup_uncharge_swap(ent); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org