[Xen-changelog] [linux-2.6.18-xen] blktap: fix race memory refernce with ring_ok.

["Xen patchbot-linux-2.6.18-xen" <patchbot-linux-2.6.18-xen@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1240922586 -3600
# Node ID 3232c6e19bdc219363446f837c4136dc9959c205
# Parent  613216635ff0d0adf114bd5106bb37ae74fff458
blktap: fix race memory refernce with ring_ok.

fix race memory refernce with ring_ok.
ring_ok is shared by mmapping process and blktap kernel thread.

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
---
 drivers/xen/blktap/blktap.c |    5 +++++
 1 files changed, 5 insertions(+)

diff -r 613216635ff0 -r 3232c6e19bdc drivers/xen/blktap/blktap.c
--- a/drivers/xen/blktap/blktap.c       Tue Apr 28 13:42:32 2009 +0100
+++ b/drivers/xen/blktap/blktap.c       Tue Apr 28 13:43:06 2009 +0100
@@ -617,6 +617,9 @@ static int blktap_release(struct inode *
        if (!info)
                return 0;
 
+       info->ring_ok = 0;
+       smp_wmb();
+
        info->dev_inuse = 0;
        DPRINTK("Freeing device [/dev/xen/blktap%d]\n",info->minor);
 
@@ -717,6 +720,7 @@ static int blktap_mmap(struct file *filp
 #endif
 
        info->vma = vma;
+       smp_wmb();
        info->ring_ok = 1;
        return 0;
  fail:
@@ -1390,6 +1394,7 @@ static void dispatch_rw_block_io(blkif_t
                WPRINTK("blktap: ring not ready for requests!\n");
                goto fail_response;
        }
+       smp_rmb();
 
        if (RING_FULL(&info->ufe_ring)) {
                WPRINTK("blktap: fe_ring is full, can't add "

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