[PATCH] swap: move destroy_swap_extents calls

sys_swapon's call to destroy_swap_extents on failure is made after the final
swap_list_unlock, which is faintly unsafe: another sys_swapon might already be
setting up that swap_info_struct.  Calling it earlier, before taking
swap_list_lock, is safe.  sys_swapoff's call to destroy_swap_extents was safe,
but likewise move it earlier, before taking the locks (once try_to_unuse has
completed, nothing can be needing the swap extents).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 5ac5333..4b39e95 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1129,6 +1129,7 @@ asmlinkage long sys_swapoff(const char __user * specialfile)
                swap_list_unlock();
                goto out_dput;
        }
+       destroy_swap_extents(p);
        down(&swapon_sem);
        swap_list_lock();
        drain_mmlist();
@@ -1139,7 +1140,6 @@ asmlinkage long sys_swapoff(const char __user * specialfile)
        swap_map = p->swap_map;
        p->swap_map = NULL;
        p->flags = 0;
-       destroy_swap_extents(p);
        swap_device_unlock(p);
        swap_list_unlock();
        up(&swapon_sem);
@@ -1531,6 +1531,7 @@ bad_swap:
                set_blocksize(bdev, p->old_block_size);
                bd_release(bdev);
        }
+       destroy_swap_extents(p);
 bad_swap_2:
        swap_list_lock();
        swap_map = p->swap_map;
@@ -1540,7 +1541,6 @@ bad_swap_2:
        if (!(swap_flags & SWAP_FLAG_PREFER))
                ++least_priority;
        swap_list_unlock();
-       destroy_swap_extents(p);
        vfree(swap_map);
        if (swap_file)
                filp_close(swap_file, NULL);