On Fri, Mar 18, 2016 at 04:58:31PM +0900, Minchan Kim wrote: > <b430e9d1c6d4> "remove compressed copy from zram in-memory" > applied swap_slot_free_notify call in *end_swap_bio_read* to > remove duplicated memory between zram and memory. > > However, with introducing rw_page in zram <8c7f01025f7b> > "zram: implement rw_page operation of zram", it became void > because rw_page doesn't need bio. > > This patch restores the function for rw_page. > > Signed-off-by: Minchan Kim <[email protected]> > --- > mm/page_io.c | 93 > ++++++++++++++++++++++++++++++++---------------------------- > 1 file changed, 50 insertions(+), 43 deletions(-) > > diff --git a/mm/page_io.c b/mm/page_io.c > index ff74e512f029..18aac7819cc9 100644 > --- a/mm/page_io.c > +++ b/mm/page_io.c > @@ -66,6 +66,54 @@ void end_swap_bio_write(struct bio *bio) > bio_put(bio); > } > > +static void swap_slot_free_notify(struct page *page) > +{ > + struct swap_info_struct *sis; > + struct gendisk *disk; > + > + /* > + * There is no guarantee that the page is in swap cache - the software > + * suspend code (at least) uses end_swap_bio_read() against a non- > + * swapcache page. So we must check PG_swapcache before proceeding with > + * this optimization. > + */ > + if (unlikely(!PageSwapCache(page))) > + return; > + > + sis = page_swap_info(page); > + if (!(sis->flags & SWP_BLKDEV)) > + return; > + > + /* > + * The swap subsystem performs lazy swap slot freeing, > + * expecting that the page will be swapped out again. > + * So we can avoid an unnecessary write if the page > + * isn't redirtied. > + * This is good for real swap storage because we can > + * reduce unnecessary I/O and enhance wear-leveling > + * if an SSD is used as the as swap device. > + * But if in-memory swap device (eg zram) is used, > + * this causes a duplicated copy between uncompressed > + * data in VM-owned memory and compressed data in > + * zram-owned memory. So let's free zram-owned memory > + * and make the VM-owned decompressed page *dirty*, > + * so the page should be swapped out somewhere again if > + * we again wish to reclaim it. > + */ > + disk = sis->bdev->bd_disk; > + if (disk->fops->swap_slot_free_notify) { > + swp_entry_t entry; > + unsigned long offset; > + > + entry.val = page_private(page); > + offset = swp_offset(entry); > + > + SetPageDirty(page); > + disk->fops->swap_slot_free_notify(sis->bdev, > + offset); > + } > +} > + > static void end_swap_bio_read(struct bio *bio) > { > struct page *page = bio->bi_io_vec[0].bv_page; > @@ -81,49 +129,7 @@ static void end_swap_bio_read(struct bio *bio) > } > > SetPageUptodate(page); > - > - /* > - * There is no guarantee that the page is in swap cache - the software > - * suspend code (at least) uses end_swap_bio_read() against a non- > - * swapcache page. So we must check PG_swapcache before proceeding with > - * this optimization. > - */ > - if (likely(PageSwapCache(page))) { > - struct swap_info_struct *sis; > - > - sis = page_swap_info(page); > - if (sis->flags & SWP_BLKDEV) { > - /* > - * The swap subsystem performs lazy swap slot freeing, > - * expecting that the page will be swapped out again. > - * So we can avoid an unnecessary write if the page > - * isn't redirtied. > - * This is good for real swap storage because we can > - * reduce unnecessary I/O and enhance wear-leveling > - * if an SSD is used as the as swap device. > - * But if in-memory swap device (eg zram) is used, > - * this causes a duplicated copy between uncompressed > - * data in VM-owned memory and compressed data in > - * zram-owned memory. So let's free zram-owned memory > - * and make the VM-owned decompressed page *dirty*, > - * so the page should be swapped out somewhere again if > - * we again wish to reclaim it. > - */ > - struct gendisk *disk = sis->bdev->bd_disk; > - if (disk->fops->swap_slot_free_notify) { > - swp_entry_t entry; > - unsigned long offset; > - > - entry.val = page_private(page); > - offset = swp_offset(entry); > - > - SetPageDirty(page); > - disk->fops->swap_slot_free_notify(sis->bdev, > - offset); > - } > - } > - } > - > + swap_slot_free_notify(page); > out: > unlock_page(page); > bio_put(bio); > @@ -347,6 +353,7 @@ int swap_readpage(struct page *page) > > ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); > if (!ret) { > + swap_slot_free_notify(page); > count_vm_event(PSWPIN); > return 0; > }
Hello, You need to check PageUpdate() or something because bdev_read_page() can be asynchronous. BTW, something like as swap_slot_free_notify() which invalidate backend of storage can also be possible for frontswap when frontswap_load() succeed. Isn't it? Thanks.
