diff options
| author | NeilBrown <neilb@suse.de> | 2014-08-04 08:24:00 +0200 |
|---|---|---|
| committer | Trond Myklebust <trond.myklebust@primarydata.com> | 2014-08-04 15:22:08 +0200 |
| commit | 50d77739fa1972030daf1c8902404551e49bf232 (patch) | |
| tree | 2e88b257ab14a66d790f5741137269965e06c444 /fs/nfs/dir.c | |
| parent | NFS: allow lockless access to access_cache (diff) | |
| download | linux-50d77739fa1972030daf1c8902404551e49bf232.tar.xz linux-50d77739fa1972030daf1c8902404551e49bf232.zip | |
NFS: fix two problems in lookup_revalidate in RCU-walk
1/ rcu_dereference isn't correct: that field isn't
RCU protected. It could potentially change at any time
so ACCESS_ONCE might be justified.
changes to ->d_parent are protected by ->d_seq. However
that isn't always checked after ->d_revalidate is called,
so it is safest to keep the double-check that ->d_parent
hasn't changed at the end of these functions.
2/ in nfs4_lookup_revalidate, "->d_parent" was forgotten.
So 'parent' was not the parent of 'dentry'.
This fails safe is the context is that dentry->d_inode is
NULL, and the result of parent->d_inode being NULL is
that ECHILD is returned, which is always safe.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Diffstat (limited to 'fs/nfs/dir.c')
| -rw-r--r-- | fs/nfs/dir.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 1b5f38f48dab..36d921f0c602 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -1102,7 +1102,7 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags) int error; if (flags & LOOKUP_RCU) { - parent = rcu_dereference(dentry->d_parent); + parent = ACCESS_ONCE(dentry->d_parent); dir = ACCESS_ONCE(parent->d_inode); if (!dir) return -ECHILD; @@ -1184,7 +1184,7 @@ out_set_verifier: nfs_advise_use_readdirplus(dir); out_valid_noent: if (flags & LOOKUP_RCU) { - if (parent != rcu_dereference(dentry->d_parent)) + if (parent != ACCESS_ONCE(dentry->d_parent)) return -ECHILD; } else dput(parent); @@ -1585,7 +1585,7 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags) struct inode *dir; if (flags & LOOKUP_RCU) { - parent = rcu_dereference(dentry); + parent = ACCESS_ONCE(dentry->d_parent); dir = ACCESS_ONCE(parent->d_inode); if (!dir) return -ECHILD; @@ -1599,7 +1599,7 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags) ret = -ECHILD; if (!(flags & LOOKUP_RCU)) dput(parent); - else if (parent != rcu_dereference(dentry)) + else if (parent != ACCESS_ONCE(dentry->d_parent)) return -ECHILD; goto out; } |