From 64672d55d93c26fb4035fd1a84a803cbc09cb058 Mon Sep 17 00:00:00 2001 From: Peter Staubach Date: Tue, 23 Dec 2008 15:21:56 -0500 Subject: optimize attribute timeouts for "noac" and "actimeo=0" Hi. I've been looking at a bugzilla which describes a problem where a customer was advised to use either the "noac" or "actimeo=0" mount options to solve a consistency problem that they were seeing in the file attributes. It turned out that this solution did not work reliably for them because sometimes, the local attribute cache was believed to be valid and not timed out. (With an attribute cache timeout of 0, the cache should always appear to be timed out.) In looking at this situation, it appears to me that the problem is that the attribute cache timeout code has an off-by-one error in it. It is assuming that the cache is valid in the region, [read_cache_jiffies, read_cache_jiffies + attrtimeo]. The cache should be considered valid only in the region, [read_cache_jiffies, read_cache_jiffies + attrtimeo). With this change, the options, "noac" and "actimeo=0", work as originally expected. This problem was previously addressed by special casing the attrtimeo == 0 case. However, since the problem is only an off- by-one error, the cleaner solution is address the off-by-one error and thus, not require the special case. Thanx... ps Signed-off-by: Peter Staubach Signed-off-by: Trond Myklebust --- include/linux/nfs_fs.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'include/linux/nfs_fs.h') diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h index b8d9c6dd4f63..db867b04ac3c 100644 --- a/include/linux/nfs_fs.h +++ b/include/linux/nfs_fs.h @@ -130,7 +130,10 @@ struct nfs_inode { * * We need to revalidate the cached attrs for this inode if * - * jiffies - read_cache_jiffies > attrtimeo + * jiffies - read_cache_jiffies >= attrtimeo + * + * Please note the comparison is greater than or equal + * so that zero timeout values can be specified. */ unsigned long read_cache_jiffies; unsigned long attrtimeo; -- cgit v1.2.2