mm: split SWP_FILE into SWP_ACTIVATED and SWP_FS

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.

Link: http://lkml.kernel.org/r/6d63d8668c4287a4f6d203d65696e96f80abdfc7.1536704650.git.osandov@fb.com
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Sterba <dsterba@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/swap.h b/include/linux/swap.h
index b93740d..38195f5 100644 (file)
--- 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 573d366..a451ffa 100644 (file)
--- 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) {
                struct kiocb kiocb;
                struct file *swap_file = sis->swap_file;
                struct address_space *mapping = swap_file->f_mapping;
@@ -365,7 +365,7 @@ 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;
 
@@ -423,7 +423,7 @@ 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 2681e50..f0c7e4c 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1003,7 +1003,7 @@ start_over:
                        goto nextsi;
                }
                if (size == SWAPFILE_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,
@@ -2299,12 +2299,13 @@ 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);
        }
 }
 
@@ -2400,8 +2401,10 @@ 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;
                }