[PATCH] swap: move destroy_swap_extents calls (4cd3bb10) · Commits · 戴 / test

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>

mm/swapfile.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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);

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