The patch titled
swapfile: swapon use discard (trim)
has been added to the -mm tree. Its filename is
swapfile-swapon-use-discard-trim.patch
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------------------------------------------------------
Subject: swapfile: swapon use discard (trim)
From: Hugh Dickins <hugh@xxxxxxxxxxx>
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@xxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
Cc: Matthew Wilcox <matthew@xxxxxx>
Cc: Joern Engel <joern@xxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: Donjun Shin <djshin90@xxxxxxxxx>
Cc: Tejun Heo <teheo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swap.h | 1 +
mm/swapfile.c | 39 +++++++++++++++++++++++++++++++++++++--
2 files changed, 38 insertions(+), 2 deletions(-)
diff -puN include/linux/swap.h~swapfile-swapon-use-discard-trim include/linux/swap.h
--- a/include/linux/swap.h~swapfile-swapon-use-discard-trim
+++ a/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 */
};
diff -puN mm/swapfile.c~swapfile-swapon-use-discard-trim mm/swapfile.c
--- a/mm/swapfile.c~swapfile-swapon-use-discard-trim
+++ a/mm/swapfile.c
@@ -84,6 +84,37 @@ void swap_unplug_io_fn(struct backing_de
up_read(&swap_unplug_sem);
}
+/*
+ * swapon tell device that all the old swap contents can be discarded,
+ * to allow the swap device to optimize its wear-levelling.
+ */
+static int discard_swap(struct swap_info_struct *si)
+{
+ struct swap_extent *se;
+ int err = 0;
+
+ list_for_each_entry(se, &si->extent_list, list) {
+ sector_t start_block = se->start_block << (PAGE_SHIFT - 9);
+ pgoff_t nr_blocks = se->nr_pages << (PAGE_SHIFT - 9);
+
+ if (se->start_page == 0) {
+ /* Do not discard the swap header page! */
+ start_block += 1 << (PAGE_SHIFT - 9);
+ nr_blocks -= 1 << (PAGE_SHIFT - 9);
+ if (!nr_blocks)
+ continue;
+ }
+
+ err = blkdev_issue_discard(si->bdev, start_block,
+ nr_blocks, GFP_KERNEL);
+ if (err)
+ break;
+
+ cond_resched();
+ }
+ return err; /* That will often be -EOPNOTSUPP */
+}
+
#define SWAPFILE_CLUSTER 256
#define LATENCY_LIMIT 256
@@ -1649,6 +1680,9 @@ asmlinkage long sys_swapon(const char __
goto bad_swap;
}
+ if (discard_swap(p) == 0)
+ p->flags |= SWP_DISCARDABLE;
+
mutex_lock(&swapon_mutex);
spin_lock(&swap_lock);
if (swap_flags & SWAP_FLAG_PREFER)
@@ -1662,9 +1696,10 @@ asmlinkage long sys_swapon(const char __
total_swap_pages += nr_good_pages;
printk(KERN_INFO "Adding %uk swap on %s. "
- "Priority:%d extents:%d across:%lluk\n",
+ "Priority:%d extents:%d across:%lluk%s\n",
nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
- nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
+ nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
+ (p->flags & SWP_DISCARDABLE) ? " D" : "");
/* insert swap space into swap_list: */
prev = -1;
_
Patches currently in -mm which might be from hugh@xxxxxxxxxxx are
linux-next.patch
mm-dont-mark_page_accessed-in-shmem_fault.patch
mm-apply_to_range-call-pte-function-with-lazy-updates.patch
mm-remove-cgroup_mm_owner_callbacks.patch
mm-remove-aop_writepage_activate.patch
mm-remove-gfp_highuser_pagecache.patch
mm-add-setclearpageswapcache-stubs.patch
mm-replace-some-bug_ons-by-vm_bug_ons.patch
mm-add_active_or_unevictable-into-rmap.patch
mm-make-page_lock_anon_vma-static.patch
mm-further-cleanup-page_add_new_anon_rmap.patch
mm-gup-persist-for-write-permission.patch
mm-wp-lock-page-before-deciding-cow.patch
mm-reuse_swap_page-replaces-can_share_swap_page.patch
mm-try_to_free_swap-replaces-remove_exclusive_swap_page.patch
mm-try_to_unuse-check-removing-right-swap.patch
mm-remove-try_to_munlock-from-vmscan.patch
mm-remove-gfp_mask-from-add_to_swap.patch
mm-add-add_to_swap-stub.patch
mm-optimize-get_scan_ratio-for-no-swap.patch
make-get_user_pages-interruptible.patch
make-get_user_pages-interruptible-update.patch
swapfile-swapon-needs-larger-size-type.patch
swapfile-remove-swp_active-mask.patch
swapfile-remove-surplus-whitespace.patch
swapfile-remove-v0-swap-space-message.patch
swapfile-rearrange-scan-and-swap_info.patch
swapfile-swapon-use-discard-trim.patch
swapfile-swap-allocation-use-discard.patch
swapfile-swapon-randomize-if-nonrot.patch
swapfile-swap-allocation-cycle-if-nonrot.patch
memcg-handle-swap-caches.patch
memcg-handle-swap-caches-build-fix.patch
memcg-swap-cgroup-for-remembering-usage.patch
memcg-memswap-controller-core.patch
memcg-memswap-controller-core-make-resize-limit-hold-mutex.patch
memcg-memswap-controller-core-swapcache-fixes.patch
prio_tree-debugging-patch.patch
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