On 25.05.2018 00:41, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@xxxxxx>
>
> The SWP_FILE flag serves two purposes: to make swap_{read,write}page()
> go through the filesystem, and to make swapoff() call
> ->swap_deactivate(). For Btrfs, we want the latter but not the former,
> so split this flag into two. This makes us always call
> ->swap_deactivate() if ->swap_activate() succeeded, not just if it
> didn't add any swap extents itself.
>
> This also resolves the issue of the very misleading name of SWP_FILE,
> which is only used for swap files over NFS.
>
> Signed-off-by: Omar Sandoval <osandov@xxxxxx>
Generally looks good:
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
just one cleanup suggestion, see below.
> ---
> include/linux/swap.h | 13 +++++++------
> mm/page_io.c | 6 +++---
> mm/swapfile.c | 13 ++++++++-----
> 3 files changed, 18 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 2417d288e016..29dfd436435c 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -167,13 +167,14 @@ enum {
> SWP_SOLIDSTATE = (1 << 4), /* blkdev seeks are cheap */
> SWP_CONTINUED = (1 << 5), /* swap_map has count continuation */
> SWP_BLKDEV = (1 << 6), /* its a block device */
> - SWP_FILE = (1 << 7), /* set after swap_activate success */
> - SWP_AREA_DISCARD = (1 << 8), /* single-time swap area discards */
> - SWP_PAGE_DISCARD = (1 << 9), /* freed swap page-cluster discards */
> - SWP_STABLE_WRITES = (1 << 10), /* no overwrite PG_writeback pages */
> - SWP_SYNCHRONOUS_IO = (1 << 11), /* synchronous IO is efficient */
> + SWP_ACTIVATED = (1 << 7), /* set after swap_activate success */
> + SWP_FS = (1 << 8), /* swap file goes through fs */
> + SWP_AREA_DISCARD = (1 << 9), /* single-time swap area discards */
> + SWP_PAGE_DISCARD = (1 << 10), /* freed swap page-cluster discards */
> + SWP_STABLE_WRITES = (1 << 11), /* no overwrite PG_writeback pages */
> + SWP_SYNCHRONOUS_IO = (1 << 12), /* synchronous IO is efficient */
> /* add others here before... */
> - SWP_SCANNING = (1 << 12), /* refcount in scan_swap_map */
> + SWP_SCANNING = (1 << 13), /* refcount in scan_swap_map */
> };
>
> #define SWAP_CLUSTER_MAX 32UL
> diff --git a/mm/page_io.c b/mm/page_io.c
> index b41cf9644585..f2d06c1d0cc1 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -283,7 +283,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
> struct swap_info_struct *sis = page_swap_info(page);
>
> VM_BUG_ON_PAGE(!PageSwapCache(page), page);
> - if (sis->flags & SWP_FILE) {
> + if (sis->flags & SWP_FS) {
Not necessarily for this series but something to keep in mind:
nit: The way the fs case is tucked onto the __swap_writepage is a bit
ugly. How about factoring out the filesystem/blockdev casae into two
functions :
__swap_writepage_fs/__swap_writepage_bdev
then in swap_writepage we just have the if (sis->flags & SWP_FS) check
and dispatch to either write_page_fs or writepage_bdev.
> struct kiocb kiocb;
> struct file *swap_file = sis->swap_file;
> struct address_space *mapping = swap_file->f_mapping;
> @@ -364,7 +364,7 @@ int swap_readpage(struct page *page, bool synchronous)
> goto out;
> }
>
> - if (sis->flags & SWP_FILE) {
> + if (sis->flags & SWP_FS) {
> struct file *swap_file = sis->swap_file;
> struct address_space *mapping = swap_file->f_mapping;
>
> @@ -422,7 +422,7 @@ int swap_set_page_dirty(struct page *page)
> {
> struct swap_info_struct *sis = page_swap_info(page);
>
> - if (sis->flags & SWP_FILE) {
> + if (sis->flags & SWP_FS) {
> struct address_space *mapping = sis->swap_file->f_mapping;
>
> VM_BUG_ON_PAGE(!PageSwapCache(page), page);
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index cc2cf04d9018..886c9d89b144 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -973,7 +973,7 @@ int get_swap_pages(int n_goal, bool cluster, swp_entry_t swp_entries[])
> goto nextsi;
> }
> if (cluster) {
> - if (!(si->flags & SWP_FILE))
> + if (!(si->flags & SWP_FS))
> n_ret = swap_alloc_cluster(si, swp_entries);
> } else
> n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
> @@ -2327,12 +2327,13 @@ static void destroy_swap_extents(struct swap_info_struct *sis)
> kfree(se);
> }
>
> - if (sis->flags & SWP_FILE) {
> + if (sis->flags & SWP_ACTIVATED) {
> struct file *swap_file = sis->swap_file;
> struct address_space *mapping = swap_file->f_mapping;
>
> - sis->flags &= ~SWP_FILE;
> - mapping->a_ops->swap_deactivate(swap_file);
> + sis->flags &= ~SWP_ACTIVATED;
> + if (mapping->a_ops->swap_deactivate)
> + mapping->a_ops->swap_deactivate(swap_file);
> }
> }
>
> @@ -2428,8 +2429,10 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
>
> if (mapping->a_ops->swap_activate) {
> ret = mapping->a_ops->swap_activate(sis, swap_file, span);
> + if (ret >= 0)
> + sis->flags |= SWP_ACTIVATED;
> if (!ret) {
> - sis->flags |= SWP_FILE;
> + sis->flags |= SWP_FS;
> ret = add_swap_extent(sis, 0, sis->max, 0);
> *span = sis->pages;
> }
>
