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authorNeilBrown <neilb@suse.de>2014-07-14 11:28:20 +1000
committerTrond Myklebust <trond.myklebust@primarydata.com>2014-08-03 17:14:11 -0400
commitd51ac1a8e9b86b2d17d349bb256869cab6522787 (patch)
treeddb2dc1a448c67d512465eaee7c73cfdbbe4bf23 /fs/nfs/dir.c
parent49317a7fdaa462b09b9bb4942b64c3a3316bd564 (diff)
NFS: prepare for RCU-walk support but pushing tests later in code.
nfs_lookup_revalidate, nfs4_lookup_revalidate, and nfs_permission all need to understand and handle RCU-walk for NFS to gain the benefits of RCU-walk for cached information. Currently these functions all immediately return -ECHILD if the relevant flag (LOOKUP_RCU or MAY_NOT_BLOCK) is set. This patch pushes those tests later in the code so that we only abort immediately before we enter rcu-unsafe code. As subsequent patches make that rcu-unsafe code rcu-safe, several of these new tests will disappear. With this patch there are several paths through the code which will no longer return -ECHILD during an RCU-walk. However these are mostly error paths or other uninteresting cases. A noteworthy change in nfs_lookup_revalidate is that we don't take (or put) the reference to ->d_parent when LOOKUP_RCU is set. Rather we rcu_dereference ->d_parent, and check that ->d_inode is not NULL. We also check that ->d_parent hasn't changed after all the tests. In nfs4_lookup_revalidate we simply avoid testing LOOKUP_RCU on the path that only calls nfs_lookup_revalidate() as that function already performs the required test. 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.c45
1 files changed, 33 insertions, 12 deletions
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 0090dae1acd3..ea12e58dfd85 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1088,21 +1088,30 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
struct nfs4_label *label = NULL;
int error;
- if (flags & LOOKUP_RCU)
- return -ECHILD;
-
- parent = dget_parent(dentry);
- dir = parent->d_inode;
+ if (flags & LOOKUP_RCU) {
+ parent = rcu_dereference(dentry->d_parent);
+ dir = ACCESS_ONCE(parent->d_inode);
+ if (!dir)
+ return -ECHILD;
+ } else {
+ parent = dget_parent(dentry);
+ dir = parent->d_inode;
+ }
nfs_inc_stats(dir, NFSIOS_DENTRYREVALIDATE);
inode = dentry->d_inode;
if (!inode) {
+ if (flags & LOOKUP_RCU)
+ return -ECHILD;
+
if (nfs_neg_need_reval(dir, dentry, flags))
goto out_bad;
goto out_valid_noent;
}
if (is_bad_inode(inode)) {
+ if (flags & LOOKUP_RCU)
+ return -ECHILD;
dfprintk(LOOKUPCACHE, "%s: %pd2 has dud inode\n",
__func__, dentry);
goto out_bad;
@@ -1111,6 +1120,9 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ))
goto out_set_verifier;
+ if (flags & LOOKUP_RCU)
+ return -ECHILD;
+
/* Force a full look up iff the parent directory has changed */
if (!nfs_is_exclusive_create(dir, flags) && nfs_check_verifier(dir, dentry)) {
if (nfs_lookup_verify_inode(inode, flags))
@@ -1153,13 +1165,18 @@ out_set_verifier:
/* Success: notify readdir to use READDIRPLUS */
nfs_advise_use_readdirplus(dir);
out_valid_noent:
- dput(parent);
+ if (flags & LOOKUP_RCU) {
+ if (parent != rcu_dereference(dentry->d_parent))
+ return -ECHILD;
+ } else
+ dput(parent);
dfprintk(LOOKUPCACHE, "NFS: %s(%pd2) is valid\n",
__func__, dentry);
return 1;
out_zap_parent:
nfs_zap_caches(dir);
out_bad:
+ WARN_ON(flags & LOOKUP_RCU);
nfs_free_fattr(fattr);
nfs_free_fhandle(fhandle);
nfs4_label_free(label);
@@ -1185,6 +1202,7 @@ out_zap_parent:
__func__, dentry);
return 0;
out_error:
+ WARN_ON(flags & LOOKUP_RCU);
nfs_free_fattr(fattr);
nfs_free_fhandle(fhandle);
nfs4_label_free(label);
@@ -1532,9 +1550,6 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
struct inode *inode;
int ret = 0;
- if (flags & LOOKUP_RCU)
- return -ECHILD;
-
if (!(flags & LOOKUP_OPEN) || (flags & LOOKUP_DIRECTORY))
goto no_open;
if (d_mountpoint(dentry))
@@ -1551,6 +1566,9 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
struct dentry *parent;
struct inode *dir;
+ if (flags & LOOKUP_RCU)
+ return -ECHILD;
+
parent = dget_parent(dentry);
dir = parent->d_inode;
if (!nfs_neg_need_reval(dir, dentry, flags))
@@ -2348,9 +2366,6 @@ int nfs_permission(struct inode *inode, int mask)
struct rpc_cred *cred;
int res = 0;
- if (mask & MAY_NOT_BLOCK)
- return -ECHILD;
-
nfs_inc_stats(inode, NFSIOS_VFSACCESS);
if ((mask & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
@@ -2377,6 +2392,9 @@ force_lookup:
if (!NFS_PROTO(inode)->access)
goto out_notsup;
+ if (mask & MAY_NOT_BLOCK)
+ return -ECHILD;
+
cred = rpc_lookup_cred();
if (!IS_ERR(cred)) {
res = nfs_do_access(inode, cred, mask);
@@ -2391,6 +2409,9 @@ out:
inode->i_sb->s_id, inode->i_ino, mask, res);
return res;
out_notsup:
+ if (mask & MAY_NOT_BLOCK)
+ return -ECHILD;
+
res = nfs_revalidate_inode(NFS_SERVER(inode), inode);
if (res == 0)
res = generic_permission(inode, mask);