From: Lachlan McIlroy <lachlan@sgi.com>
To: xfs-dev <xfs-dev@sgi.com>, xfs-oss <xfs@oss.sgi.com>
Subject: [PATCH] Do not access buffers after dropping reference count
Date: Tue, 22 Jul 2008 12:16:45 +1000 [thread overview]
Message-ID: <4885430D.7000506@sgi.com> (raw)
We should not access a buffer after dropping it's reference count otherwise
we could race with another thread that releases the final reference count
and frees the buffer causing us to access potentially unmapped memory.
Lachlan
--- fs/xfs/linux-2.6/xfs_buf.c_1.257 2008-07-16 17:38:00.000000000 +1000
+++ fs/xfs/linux-2.6/xfs_buf.c 2008-07-22 12:05:50.000000000 +1000
@@ -839,6 +839,7 @@ xfs_buf_rele(
return;
}
+ ASSERT(atomic_read(&bp->b_hold) > 0);
if (atomic_dec_and_lock(&bp->b_hold, &hash->bh_lock)) {
if (bp->b_relse) {
atomic_inc(&bp->b_hold);
@@ -852,11 +853,6 @@ xfs_buf_rele(
spin_unlock(&hash->bh_lock);
xfs_buf_free(bp);
}
- } else {
- /*
- * Catch reference count leaks
- */
- ASSERT(atomic_read(&bp->b_hold) >= 0);
}
}
next reply other threads:[~2008-07-22 2:10 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-22 2:16 Lachlan McIlroy [this message]
2008-07-22 2:24 ` [PATCH] Do not access buffers after dropping reference count Dave Chinner
2008-07-22 2:55 ` Lachlan McIlroy
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