From 6a6ba83175c029c7820765bae44692266b29e67a Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 6 Jan 2009 14:39:51 -0800 Subject: swapfile: swapon use discard (trim) When adding swap, all the old data on swap can be forgotten: sys_swapon() discard all but the header page of the swap partition (or every extent but the header of the swap file), to give a solidstate swap device the opportunity to optimize its wear-levelling. If that succeeds, note SWP_DISCARDABLE for later use, and report it with a "D" at the right end of the kernel's "Adding ... swap" message. Perhaps something should be shown in /proc/swaps (swapon -s), but we have to be more cautious before making any addition to that format. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Nick Piggin Cc: David Woodhouse Cc: Jens Axboe Cc: Matthew Wilcox Cc: Joern Engel Cc: James Bottomley Cc: Donjun Shin Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/swap.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/swap.h') diff --git a/include/linux/swap.h b/include/linux/swap.h index 9cabb8b21ab..0b9210ea96c 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -120,6 +120,7 @@ struct swap_extent { enum { SWP_USED = (1 << 0), /* is slot in swap_info[] used? */ SWP_WRITEOK = (1 << 1), /* ok to write to this swap? */ + SWP_DISCARDABLE = (1 << 2), /* blkdev supports discard */ /* add others here before... */ SWP_SCANNING = (1 << 8), /* refcount in scan_swap_map */ }; -- cgit v1.2.3