NFS: Fix the resolution problem with nfs_inode_attrs_need_update()
It appears that 'jiffies' timestamps do not have high enough resolution for
nfs_inode_attrs_need_update(). One problem is that a GETATTR can be
launched within < 1 jiffy of the last operation that updated the attribute.
Another problem is that RPC calls can take < 1 jiffy to execute.
We can fix this by switching the variables to use a simple global counter
that gets incremented every time we start another GETATTR call.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 49d5654..4807074 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -156,6 +156,7 @@
decode_dirent_t decode;
int plus;
unsigned long timestamp;
+ unsigned long gencount;
int timestamp_valid;
} nfs_readdir_descriptor_t;
@@ -177,7 +178,7 @@
struct file *file = desc->file;
struct inode *inode = file->f_path.dentry->d_inode;
struct rpc_cred *cred = nfs_file_cred(file);
- unsigned long timestamp;
+ unsigned long timestamp, gencount;
int error;
dfprintk(DIRCACHE, "NFS: %s: reading cookie %Lu into page %lu\n",
@@ -186,6 +187,7 @@
again:
timestamp = jiffies;
+ gencount = nfs_inc_attr_generation_counter();
error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, desc->entry->cookie, page,
NFS_SERVER(inode)->dtsize, desc->plus);
if (error < 0) {
@@ -199,6 +201,7 @@
goto error;
}
desc->timestamp = timestamp;
+ desc->gencount = gencount;
desc->timestamp_valid = 1;
SetPageUptodate(page);
/* Ensure consistent page alignment of the data.
@@ -224,9 +227,10 @@
if (IS_ERR(p))
return PTR_ERR(p);
desc->ptr = p;
- if (desc->timestamp_valid)
+ if (desc->timestamp_valid) {
desc->entry->fattr->time_start = desc->timestamp;
- else
+ desc->entry->fattr->gencount = desc->gencount;
+ } else
desc->entry->fattr->valid &= ~NFS_ATTR_FATTR;
return 0;
}
@@ -471,7 +475,7 @@
struct rpc_cred *cred = nfs_file_cred(file);
struct page *page = NULL;
int status;
- unsigned long timestamp;
+ unsigned long timestamp, gencount;
dfprintk(DIRCACHE, "NFS: uncached_readdir() searching for cookie %Lu\n",
(unsigned long long)*desc->dir_cookie);
@@ -482,6 +486,7 @@
goto out;
}
timestamp = jiffies;
+ gencount = nfs_inc_attr_generation_counter();
status = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred,
*desc->dir_cookie, page,
NFS_SERVER(inode)->dtsize,
@@ -490,6 +495,7 @@
desc->ptr = kmap(page); /* matching kunmap in nfs_do_filldir */
if (status >= 0) {
desc->timestamp = timestamp;
+ desc->gencount = gencount;
desc->timestamp_valid = 1;
if ((status = dir_decode(desc)) == 0)
desc->entry->prev_cookie = *desc->dir_cookie;
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index de3f11e..116a3bd 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -305,7 +305,7 @@
init_special_inode(inode, inode->i_mode, fattr->rdev);
nfsi->read_cache_jiffies = fattr->time_start;
- nfsi->last_updated = now;
+ nfsi->attr_gencount = fattr->gencount;
nfsi->cache_change_attribute = now;
inode->i_atime = fattr->atime;
inode->i_mtime = fattr->mtime;
@@ -909,6 +909,30 @@
return nfs_size_to_loff_t(fattr->size) > i_size_read(inode);
}
+static unsigned long nfs_attr_generation_counter;
+
+static unsigned long nfs_read_attr_generation_counter(void)
+{
+ smp_rmb();
+ return nfs_attr_generation_counter;
+}
+
+unsigned long nfs_inc_attr_generation_counter(void)
+{
+ unsigned long ret;
+ smp_rmb();
+ ret = ++nfs_attr_generation_counter;
+ smp_wmb();
+ return ret;
+}
+
+void nfs_fattr_init(struct nfs_fattr *fattr)
+{
+ fattr->valid = 0;
+ fattr->time_start = jiffies;
+ fattr->gencount = nfs_inc_attr_generation_counter();
+}
+
/**
* nfs_inode_attrs_need_update - check if the inode attributes need updating
* @inode - pointer to inode
@@ -922,8 +946,7 @@
* catch the case where ctime either didn't change, or went backwards
* (if someone reset the clock on the server) by looking at whether
* or not this RPC call was started after the inode was last updated.
- * Note also the check for jiffy wraparound if the last_updated timestamp
- * is later than 'jiffies'.
+ * Note also the check for wraparound of 'attr_gencount'
*
* The function returns 'true' if it thinks the attributes in 'fattr' are
* more recent than the ones cached in the inode.
@@ -933,10 +956,10 @@
{
const struct nfs_inode *nfsi = NFS_I(inode);
- return time_after(fattr->time_start, nfsi->last_updated) ||
+ return ((long)fattr->gencount - (long)nfsi->attr_gencount) > 0 ||
nfs_ctime_need_update(inode, fattr) ||
nfs_size_need_update(inode, fattr) ||
- time_after(nfsi->last_updated, jiffies);
+ ((long)nfsi->attr_gencount - (long)nfs_read_attr_generation_counter() > 0);
}
static int nfs_refresh_inode_locked(struct inode *inode, struct nfs_fattr *fattr)
@@ -1107,7 +1130,7 @@
}
/* 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;
+ invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
} else if (nfsi->change_attr != fattr->change_attr) {
dprintk("NFS: change_attr change on server for file %s/%ld\n",
inode->i_sb->s_id, inode->i_ino);
@@ -1163,7 +1186,7 @@
nfs_inc_stats(inode, NFSIOS_ATTRINVALIDATE);
nfsi->attrtimeo = NFS_MINATTRTIMEO(inode);
nfsi->attrtimeo_timestamp = now;
- nfsi->last_updated = now;
+ nfsi->attr_gencount = nfs_inc_attr_generation_counter();
} else {
if (!time_in_range(now, nfsi->attrtimeo_timestamp, nfsi->attrtimeo_timestamp + nfsi->attrtimeo)) {
if ((nfsi->attrtimeo <<= 1) > NFS_MAXATTRTIMEO(inode))
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index ca563ee..ac8d023 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -137,7 +137,7 @@
unsigned long attrtimeo_timestamp;
__u64 change_attr; /* v4 only */
- unsigned long last_updated;
+ unsigned long attr_gencount;
/* "Generation counter" for the attribute cache. This is
* bumped whenever we update the metadata on the
* server.
@@ -344,15 +344,11 @@
extern void put_nfs_open_context(struct nfs_open_context *ctx);
extern struct nfs_open_context *nfs_find_open_context(struct inode *inode, struct rpc_cred *cred, int mode);
extern u64 nfs_compat_user_ino64(u64 fileid);
+extern void nfs_fattr_init(struct nfs_fattr *fattr);
/* linux/net/ipv4/ipconfig.c: trims ip addr off front of name, too. */
extern __be32 root_nfs_parse_addr(char *name); /*__init*/
-
-static inline void nfs_fattr_init(struct nfs_fattr *fattr)
-{
- fattr->valid = 0;
- fattr->time_start = jiffies;
-}
+extern unsigned long nfs_inc_attr_generation_counter(void);
/*
* linux/fs/nfs/file.c
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 6ee6ae3..c1c31ac 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -56,6 +56,7 @@
__u64 change_attr; /* NFSv4 change attribute */
__u64 pre_change_attr;/* pre-op NFSv4 change attribute */
unsigned long time_start;
+ unsigned long gencount;
};
#define NFS_ATTR_WCC 0x0001 /* pre-op WCC data */