Messages in this thread Patch in this message | | | Subject | Re: Cache invalidation bug in NFS v3 - trivially reproducible | From | Trond Myklebust <> | Date | Thu, 13 Oct 2005 18:34:14 -0400 |
| |
ty den 11.10.2005 Klokka 11:09 (+0200) skreiv Leif Nixon: > Hi, > > We have come across a bug where a NFS v3 client fails to invalidate > its data cache for a file even though it realizes that the file > attributes have changed. We have been able to recreate the bug on a > range of kernel versions and different underlying file systems. > > Here's a minimal way to reproduce the error (there seems to be some > timing issues involved, but this has worked at least 90% of the time): > > NFS client n1 NFS client n2 > > $ echo 1 > f > $ cat f > 1 > $ touch . > $ echo 2 > f > $ touch f > $ cat f > 1 > > Now client n2 is stuck in a state where it uses its old cached data > forever (or at least for several hours): > > NFS client n1 NFS client n2 > > $ cat f > 2 > $ cat f > 1 > > However, "stat f" gives the same output on both clients. "touch f" on > either machine corrects the situation; n2 invalidates its data cache. > > Interestingly, the second write to the file ("echo 2 > f") must > not change the size of the file. If you do "echo foo > f" instead, > the erroneous behaviour isn't triggered. > > We have seen this on a range of kernels between 2.6.9 and 2.6.13.2 on > Debian, CentOS, RHEL, Fedora and vanilla kernel.org, on both clients > and server. We have *not* been able to reproduce the bug with Linux > clients and a Solaris server, neither with Solaris clients and a Linux > server. Underlying file systems have been ext3 and xfs (and Solaris > ufs). We have tried varying mount options, but to no avail; the bug > persists, even with "noac".
Does the attached patch help?
Cheers, Trond
NFS: Fix cache consistency races
If the data cache has been marked as potentially invalid by nfs_refresh_inode, we should invalidate it rather than assume that changes are due to our own activity.
Also ensure that we always start with a valid cache before declaring it to be protected by a delegation.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> --- delegation.c | 4 ++++ file.c | 3 ++- inode.c | 7 ++----- 3 files changed, 8 insertions(+), 6 deletions(-)
Index: linux-2.6.14-rc4/fs/nfs/delegation.c =================================================================== --- linux-2.6.14-rc4.orig/fs/nfs/delegation.c +++ linux-2.6.14-rc4/fs/nfs/delegation.c @@ -85,6 +85,10 @@ int nfs_inode_set_delegation(struct inod struct nfs_delegation *delegation; int status = 0; + /* Ensure we first revalidate the attributes and page cache! */ + if ((nfsi->cache_validity & (NFS_INO_REVAL_PAGECACHE|NFS_INO_INVALID_ATTR))) + __nfs_revalidate_inode(NFS_SERVER(inode), inode); + delegation = nfs_alloc_delegation(); if (delegation == NULL) return -ENOMEM; Index: linux-2.6.14-rc4/fs/nfs/file.c =================================================================== --- linux-2.6.14-rc4.orig/fs/nfs/file.c +++ linux-2.6.14-rc4/fs/nfs/file.c @@ -137,7 +137,8 @@ static int nfs_revalidate_file(struct in struct nfs_inode *nfsi = NFS_I(inode); int retval = 0; - if ((nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE) || nfs_attribute_timeout(inode)) + if ((nfsi->cache_validity & (NFS_INO_REVAL_PAGECACHE|NFS_INO_INVALID_ATTR)) + || nfs_attribute_timeout(inode)) retval = __nfs_revalidate_inode(NFS_SERVER(inode), inode); nfs_revalidate_mapping(inode, filp->f_mapping); return 0; Index: linux-2.6.14-rc4/fs/nfs/inode.c =================================================================== --- linux-2.6.14-rc4.orig/fs/nfs/inode.c +++ linux-2.6.14-rc4/fs/nfs/inode.c @@ -1226,10 +1226,6 @@ int nfs_refresh_inode(struct inode *inod loff_t cur_size, new_isize; int data_unstable; - /* Do we hold a delegation? */ - if (nfs_have_delegation(inode, FMODE_READ)) - return 0; - spin_lock(&inode->i_lock); /* Are we in the process of updating data on the server? */ @@ -1350,7 +1346,8 @@ static int nfs_update_inode(struct inode nfsi->read_cache_jiffies = fattr->timestamp; /* Are we racing with known updates of the metadata on the server? */ - data_unstable = ! nfs_verify_change_attribute(inode, verifier); + data_unstable = ! (nfs_verify_change_attribute(inode, verifier) || + (nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE)); /* Check if our cached file size is stale */ new_isize = nfs_size_to_loff_t(fattr->size); | |