From b3a27d0529c6e5206f1b60f60263e3ecfd0d77cb Mon Sep 17 00:00:00 2001 From: Nitin Gupta Date: Mon, 17 May 2010 11:02:43 +0530 Subject: [PATCH] swap: Add swap slot free callback to block_device_operations This callback is required when RAM based devices are used as swap disks. One such device is ramzswap which is used as compressed in-memory swap disk. For such devices, we need a callback as soon as a swap slot is no longer used to allow freeing memory allocated for this slot. Without this callback, stale data can quickly accumulate in memory defeating the whole purpose of such devices. Signed-off-by: Nitin Gupta Acked-by: Linus Torvalds Acked-by: Nigel Cunningham Acked-by: Pekka Enberg Reviewed-by: Minchan Kim Signed-off-by: Greg Kroah-Hartman --- include/linux/blkdev.h | 2 ++ mm/swapfile.c | 4 ++++ 2 files changed, 6 insertions(+) diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 6690e8bae7bb..413284a51ccc 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1287,6 +1287,8 @@ struct block_device_operations { unsigned long long); int (*revalidate_disk) (struct gendisk *); int (*getgeo)(struct block_device *, struct hd_geometry *); + /* this callback is with swap_lock and sometimes page table lock held */ + void (*swap_slot_free_notify) (struct block_device *, unsigned long); struct module *owner; }; diff --git a/mm/swapfile.c b/mm/swapfile.c index ecb069e213d0..f5ccc476aa51 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -574,6 +574,7 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, /* free if no reference */ if (!usage) { + struct gendisk *disk = p->bdev->bd_disk; if (offset < p->lowest_bit) p->lowest_bit = offset; if (offset > p->highest_bit) @@ -583,6 +584,9 @@ static unsigned char swap_entry_free(struct swap_info_struct *p, swap_list.next = p->type; nr_swap_pages++; p->inuse_pages--; + if ((p->flags & SWP_BLKDEV) && + disk->fops->swap_slot_free_notify) + disk->fops->swap_slot_free_notify(p->bdev, offset); } return usage; -- 2.20.1