swap: Add flag to identify block swap devices

Added SWP_BLKDEV flag to distinguish block and regular file backed
swap devices. We could also check if a swap is entire block device,
rather than a file, by:
S_ISBLK(swap_info_struct->swap_file->f_mapping->host->i_mode)
but, I think, simply checking this flag is more convenient.

Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Nigel Cunningham <nigel@tuxonice.net>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 1f59d9340c4d..ec2b7a42b45f 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -146,6 +146,7 @@ enum {
         SWP_DISCARDING  = (1 << 3),     /* now discarding a free cluster */
         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 */
                                         /* add others here before... */
         SWP_SCANNING    = (1 << 8),     /* refcount in scan_swap_map */
 };
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 6cd0a8f90dc7..ecb069e213d0 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1884,6 +1884,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
                 if (error < 0)
                         goto bad_swap;
                 p->bdev = bdev;
+                p->flags |= SWP_BLKDEV;
         } else if (S_ISREG(inode->i_mode)) {
                 p->bdev = inode->i_sb->s_bdev;
                 mutex_lock(&inode->i_mutex);