NFS: Fix a wraparound issue with nfsi->cache_change_attribute

Fix wraparound issue with nfsi->cache_change_attribute. If it is found
to lie in the future, then update it to lie in the past. Patch based on
a suggestion by Neil Brown.

..and minor micro-optimisation: avoid reading 'jiffies' more than once in
nfs_update_inode().

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 4ef4547..93269c3 100644 (file)
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -939,6 +939,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
        struct nfs_inode *nfsi = NFS_I(inode);
        loff_t cur_isize, new_isize;
        unsigned int    invalid = 0;
+       unsigned long now = jiffies;
        int data_stable;
 
        dfprintk(VFS, "NFS: %s(%s/%ld ct=%d info=0x%x)\n",
@@ -964,7 +965,11 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
         * Update the read time so we don't revalidate too often.
         */
        nfsi->read_cache_jiffies = fattr->time_start;
-       nfsi->last_updated = jiffies;
+       nfsi->last_updated = now;
+
+       /* Fix a wraparound issue with nfsi->cache_change_attribute */
+       if (time_before(now, nfsi->cache_change_attribute))
+               nfsi->cache_change_attribute = now - 600*HZ;
 
        /* Are we racing with known updates of the metadata on the server? */
        data_stable = nfs_verify_change_attribute(inode, fattr->time_start);
@@ -990,7 +995,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
                        inode->i_size = new_isize;
                        invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA;
                }
-               nfsi->cache_change_attribute = jiffies;
+               nfsi->cache_change_attribute = now;
                dprintk("NFS: isize change on server for file %s/%ld\n",
                                inode->i_sb->s_id, inode->i_ino);
        }
@@ -1001,14 +1006,14 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
                dprintk("NFS: mtime change on server for file %s/%ld\n",
                                inode->i_sb->s_id, inode->i_ino);
                invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA;
-               nfsi->cache_change_attribute = jiffies;
+               nfsi->cache_change_attribute = now;
        }
 
        /* If ctime has changed we should definitely clear access+acl caches */
        if (!timespec_equal(&inode->i_ctime, &fattr->ctime)) {
                invalid |= NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
                memcpy(&inode->i_ctime, &fattr->ctime, sizeof(inode->i_ctime));
-               nfsi->cache_change_attribute = jiffies;
+               nfsi->cache_change_attribute = now;
        }
        memcpy(&inode->i_atime, &fattr->atime, sizeof(inode->i_atime));
 
@@ -1037,18 +1042,18 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
                                inode->i_sb->s_id, inode->i_ino);
                nfsi->change_attr = fattr->change_attr;
                invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA|NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
-               nfsi->cache_change_attribute = jiffies;
+               nfsi->cache_change_attribute = now;
        }
 
        /* Update attrtimeo value if we're out of the unstable period */
        if (invalid & NFS_INO_INVALID_ATTR) {
                nfs_inc_stats(inode, NFSIOS_ATTRINVALIDATE);
                nfsi->attrtimeo = NFS_MINATTRTIMEO(inode);
-               nfsi->attrtimeo_timestamp = jiffies;
-       } else if (time_after(jiffies, nfsi->attrtimeo_timestamp+nfsi->attrtimeo)) {
+               nfsi->attrtimeo_timestamp = now;
+       } else if (time_after(now, nfsi->attrtimeo_timestamp+nfsi->attrtimeo)) {
                if ((nfsi->attrtimeo <<= 1) > NFS_MAXATTRTIMEO(inode))
                        nfsi->attrtimeo = NFS_MAXATTRTIMEO(inode);
-               nfsi->attrtimeo_timestamp = jiffies;
+               nfsi->attrtimeo_timestamp = now;
        }
        /* Don't invalidate the data if we were to blame */
        if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)