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authorHugh Dickins <hugh@veritas.com>2009-01-06 14:39:51 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-06 15:59:05 -0800
commit6a6ba83175c029c7820765bae44692266b29e67a (patch)
tree30bfb4938c73b715eb90dd15c09777fe0bbf93e6 /include/linux
parentebebbbe904634b0ca1c674457b399f68db5e05b1 (diff)
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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 <hugh@veritas.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Matthew Wilcox <matthew@wil.cx> Cc: Joern Engel <joern@logfs.org> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: Donjun Shin <djshin90@gmail.com> Cc: Tejun Heo <teheo@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/swap.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 9cabb8b..0b9210e 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 */
};
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