[PATCH 2.6.28?] don't unlink an active swapfile

[Hugh Dickins]

Peter Cordes is sorry that he rm'ed his swapfiles while they were in use,
he then had no pathname to swapoff.  It's a curious little oversight, but
not one worth a lot of hackery.  Kudos to Willy Tarreau for turning this
around from a discussion of synthetic pathnames to how to prevent unlink.
Mimic immutable: prohibit unlinking an active swapfile in may_delete()
(and don't worry my little head over the tiny race window).

Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
---
Perhaps this is too late for 2.6.28: your decision.

 fs/namei.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 2.6.28-rc4/fs/namei.c	2008-10-24 09:28:19.000000000 +0100
+++ linux/fs/namei.c	2008-11-12 11:52:44.000000000 +0000
@@ -1378,7 +1378,7 @@ static int may_delete(struct inode *dir,
 	if (IS_APPEND(dir))
 		return -EPERM;
 	if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
-	    IS_IMMUTABLE(victim->d_inode))
+	    IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
 		return -EPERM;
 	if (isdir) {
 		if (!S_ISDIR(victim->d_inode->i_mode))
--
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