mm: move responsibility for setting SWP_FS_OPS to ->swap_activate

If a filesystem wishes to handle all swap IO itself (via ->direct_IO and
->readpage), rather than just providing devices addresses for
submit_bio(), SWP_FS_OPS must be set.

Currently the protocol for setting this it to have ->swap_activate return
zero.  In that case SWP_FS_OPS is set, and add_swap_extent() is called for
the entire file.

This is a little clumsy as different return values for ->swap_activate
have quite different meanings, and it makes it hard to search for which
filesystems require SWP_FS_OPS to be set.

So remove the special meaning of a zero return, and require the filesystem
to set SWP_FS_OPS if it so desires, and to always call add_swap_extent()
as required.

Currently only NFS and CIFS return zero for add_swap_extent().

Link: https://lkml.kernel.org/r/164859778123.29473.17908205846599043598.stgit@noble.brown
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: David Howells <dhowells@redhat.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index d511a78..14d2940 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4933,7 +4933,8 @@ static int cifs_swap_activate(struct swap_info_struct *sis,
         * from reading or writing the file
         */
 
-       return 0;
+       sis->flags |= SWP_FS_OPS;
+       return add_swap_extent(sis, 0, sis->max, 0);
 }
 
 static void cifs_swap_deactivate(struct file *file)

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 150b7fa..a3a0736 100644 (file)
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -483,6 +483,7 @@ static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file,
 {
        unsigned long blocks;
        long long isize;
+       int ret;
        struct inode *inode = file_inode(file);
        struct rpc_clnt *clnt = NFS_CLIENT(inode);
        struct nfs_client *cl = NFS_SERVER(inode)->nfs_client;
@@ -496,13 +497,22 @@ static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file,
                return -EINVAL;
        }
 
-       *span = sis->pages;
+       ret = rpc_clnt_swap_activate(clnt);
+       if (ret)
+               return ret;
+       ret = add_swap_extent(sis, 0, sis->max, 0);
+       if (ret < 0) {
+               rpc_clnt_swap_deactivate(clnt);
+               return ret;
+       }
 
+       *span = sis->pages;
 
        if (cl->rpc_ops->enable_swap)
                cl->rpc_ops->enable_swap(inode);
 
-       return rpc_clnt_swap_activate(clnt);
+       sis->flags |= SWP_FS_OPS;
+       return ret;
 }
 
 static void nfs_swap_deactivate(struct file *file)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 8170254..7daae5a 100644 (file)
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -577,6 +577,12 @@ static inline swp_entry_t get_swap_page(struct page *page)
        return entry;
 }
 
+static inline int add_swap_extent(struct swap_info_struct *sis,
+                                 unsigned long start_page,
+                                 unsigned long nr_pages, sector_t start_block)
+{
+       return -EINVAL;
+}
 #endif /* CONFIG_SWAP */
 
 #ifdef CONFIG_THP_SWAP

diff --git a/mm/swapfile.c b/mm/swapfile.c
index f08bf67..d811458 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2259,13 +2259,9 @@ 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_FS_OPS;
-                       ret = add_swap_extent(sis, 0, sis->max, 0);
-                       *span = sis->pages;
-               }
+               if (ret < 0)
+                       return ret;
+               sis->flags |= SWP_ACTIVATED;
                return ret;
        }