On May 5, 2008, at 11:23 AM, Trond Myklebust wrote:
On Mon, 2008-05-05 at 11:02 -0400, Chuck Lever wrote:
Hi Trond-
On May 2, 2008, at 4:25 PM, Trond Myklebust wrote:
Both the 'noac' and 'actimeo=0' mount options should ensure that
attributes
are not cached, however a bug in nfs_attribute_timeout() means that
currently, the attributes may in fact get cached for up to one
jiffy. This
has been seen to cause corruption in some applications.
The reason for the bug is that the time_in_range() test returns
'true' as
long as the current time lies between nfsi->read_cache_jiffies and
nfsi->read_cache_jiffies + nfsi->attrtimeo. In other words, if
jiffies
equals nfsi->read_cache_jiffies, then we still cache the attribute
data.
Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
---
fs/nfs/inode.c | 7 +++++++
1 files changed, 7 insertions(+), 0 deletions(-)
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 5cb3345..38f06d3 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -707,6 +707,13 @@ int nfs_attribute_timeout(struct inode *inode)
if (nfs_have_delegation(inode, FMODE_READ))
return 0;
+ /*
+ * Special case: if the attribute timeout is set to 0, then we
+ * treat the cache as having expired (unless we
+ * have a delegation).
+ */
+ if (nfsi->attrtimeo == 0)
+ return 1;
return !time_in_range(jiffies, nfsi->read_cache_jiffies, nfsi-
read_cache_jiffies + nfsi->attrtimeo);
}
Do nfs_access_get_cached() and nfs_update_inode() have the same
issue?
nfs_access_get_cached() probably has the same issue, but I can't see
how
nfs_update_inode() would. Could you explain?
nfs_update_inode() is the only other place that actually uses the
value of nfsi->attrtimeo (and it uses it with time_in_range). I'm
merely asking if we have verified that the behavior is correct if nfsi-
>attrtimeo == 0.
The logic there is abstruse, so it's difficult to tell if the (nfsi-
>attrtimeo == 0) case is behaving as expected. I don't see any
obvious problem with it right now.
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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