NFS: Fix a race in sillyrename

lookup() and sillyrename() can race one another because the sillyrename()
completion cannot take the parent directory's inode->i_mutex since the
latter may be held by whoever is calling dput().

We therefore have little option but to add extra locking to ensure that
nfs_lookup() and nfs_atomic_open() do not race with the sillyrename
completion.
If somebody has looked up the sillyrenamed file in the meantime, we just
transfer the sillydelete information to the new dentry.

Please refer to the bug-report at
	http://bugzilla.linux-nfs.org/show_bug.cgi?id=150

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

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 8ec7fbd8240c2ed37c24e0f342b72c90a1a3a212..35334539d9475dc0188bdb80f4a1d15ef70b56a9 100644 (file)
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -562,6 +562,7 @@ static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
        nfs_fattr_init(&fattr);
        desc->entry = &my_entry;
 
+       nfs_block_sillyrename(dentry);
        while(!desc->entry->eof) {
                res = readdir_search_pagecache(desc);
 
@@ -592,6 +593,7 @@ static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
                        break;
                }
        }
+       nfs_unblock_sillyrename(dentry);
        unlock_kernel();
        if (res > 0)
                res = 0;
@@ -866,6 +868,7 @@ struct dentry_operations nfs_dentry_operations = {
 static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *nd)
 {
        struct dentry *res;
+       struct dentry *parent;
        struct inode *inode = NULL;
        int error;
        struct nfs_fh fhandle;
@@ -894,26 +897,31 @@ static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, stru
                goto out_unlock;
        }
 
+       parent = dentry->d_parent;
+       /* Protect against concurrent sillydeletes */
+       nfs_block_sillyrename(parent);
        error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr);
        if (error == -ENOENT)
                goto no_entry;
        if (error < 0) {
                res = ERR_PTR(error);
-               goto out_unlock;
+               goto out_unblock_sillyrename;
        }
        inode = nfs_fhget(dentry->d_sb, &fhandle, &fattr);
        res = (struct dentry *)inode;
        if (IS_ERR(res))
-               goto out_unlock;
+               goto out_unblock_sillyrename;
 
 no_entry:
        res = d_materialise_unique(dentry, inode);
        if (res != NULL) {
                if (IS_ERR(res))
-                       goto out_unlock;
+                       goto out_unblock_sillyrename;
                dentry = res;
        }
        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
+out_unblock_sillyrename:
+       nfs_unblock_sillyrename(parent);
 out_unlock:
        unlock_kernel();
 out:

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 6d2f2a3eccf878d5cdd1e45fcbc794c7e63e9af3..173e294dffc582955ece54a2f5bab0ada992dacb 100644 (file)
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1169,6 +1169,9 @@ static void init_once(struct kmem_cache * cachep, void *foo)
        INIT_RADIX_TREE(&nfsi->nfs_page_tree, GFP_ATOMIC);
        nfsi->ncommit = 0;
        nfsi->npages = 0;
+       atomic_set(&nfsi->silly_count, 1);
+       INIT_HLIST_HEAD(&nfsi->silly_list);
+       init_waitqueue_head(&nfsi->waitqueue);
        nfs4_init_once(nfsi);
 }
 

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index cb99fd90a9acc5147135bb70846517ad8e79165e..2cb3b8b71ee7aa141aafb169ff01f47366df3281 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1372,6 +1372,7 @@ static int nfs4_intent_set_file(struct nameidata *nd, struct path *path, struct
 struct dentry *
 nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 {
+       struct dentry *parent;
        struct path path = {
                .mnt = nd->mnt,
                .dentry = dentry,
@@ -1394,6 +1395,9 @@ nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
        cred = rpcauth_lookupcred(NFS_CLIENT(dir)->cl_auth, 0);
        if (IS_ERR(cred))
                return (struct dentry *)cred;
+       parent = dentry->d_parent;
+       /* Protect against concurrent sillydeletes */
+       nfs_block_sillyrename(parent);
        state = nfs4_do_open(dir, &path, nd->intent.open.flags, &attr, cred);
        put_rpccred(cred);
        if (IS_ERR(state)) {
@@ -1401,12 +1405,14 @@ nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
                        d_add(dentry, NULL);
                        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
                }
+               nfs_unblock_sillyrename(parent);
                return (struct dentry *)state;
        }
        res = d_add_unique(dentry, igrab(state->inode));
        if (res != NULL)
                path.dentry = res;
        nfs_set_verifier(path.dentry, nfs_save_change_attribute(dir));
+       nfs_unblock_sillyrename(parent);
        nfs4_intent_set_file(nd, &path, state);
        return res;
 }

diff --git a/fs/nfs/unlink.c b/fs/nfs/unlink.c
index 1aed850d18f2ebab29f2b6b7077f4effb85413ff..6ecd46c967c8bc3073cc3389ec65d32524d23e9d 100644 (file)
--- a/fs/nfs/unlink.c
+++ b/fs/nfs/unlink.c
@@ -14,6 +14,7 @@
 
 
 struct nfs_unlinkdata {
+       struct hlist_node list;
        struct nfs_removeargs args;
        struct nfs_removeres res;
        struct inode *dir;
@@ -52,6 +53,20 @@ static int nfs_copy_dname(struct dentry *dentry, struct nfs_unlinkdata *data)
        return 0;
 }
 
+static void nfs_free_dname(struct nfs_unlinkdata *data)
+{
+       kfree(data->args.name.name);
+       data->args.name.name = NULL;
+       data->args.name.len = 0;
+}
+
+static void nfs_dec_sillycount(struct inode *dir)
+{
+       struct nfs_inode *nfsi = NFS_I(dir);
+       if (atomic_dec_return(&nfsi->silly_count) == 1)
+               wake_up(&nfsi->waitqueue);
+}
+
 /**
  * nfs_async_unlink_init - Initialize the RPC info
  * task: rpc_task of the sillydelete
@@ -95,6 +110,8 @@ static void nfs_async_unlink_done(struct rpc_task *task, void *calldata)
 static void nfs_async_unlink_release(void *calldata)
 {
        struct nfs_unlinkdata   *data = calldata;
+
+       nfs_dec_sillycount(data->dir);
        nfs_free_unlinkdata(data);
 }
 
@@ -104,33 +121,100 @@ static const struct rpc_call_ops nfs_unlink_ops = {
        .rpc_release = nfs_async_unlink_release,
 };
 
-static int nfs_call_unlink(struct dentry *dentry, struct nfs_unlinkdata *data)
+static int nfs_do_call_unlink(struct dentry *parent, struct inode *dir, struct nfs_unlinkdata *data)
 {
        struct rpc_task *task;
+       struct dentry *alias;
+
+       alias = d_lookup(parent, &data->args.name);
+       if (alias != NULL) {
+               int ret = 0;
+               /*
+                * Hey, we raced with lookup... See if we need to transfer
+                * the sillyrename information to the aliased dentry.
+                */
+               nfs_free_dname(data);
+               spin_lock(&alias->d_lock);
+               if (!(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
+                       alias->d_fsdata = data;
+                       alias->d_flags ^= DCACHE_NFSFS_RENAMED;
+                       ret = 1;
+               }
+               spin_unlock(&alias->d_lock);
+               nfs_dec_sillycount(dir);
+               dput(alias);
+               return ret;
+       }
+       data->dir = igrab(dir);
+       if (!data->dir) {
+               nfs_dec_sillycount(dir);
+               return 0;
+       }
+       data->args.fh = NFS_FH(dir);
+       nfs_fattr_init(&data->res.dir_attr);
+
+       task = rpc_run_task(NFS_CLIENT(dir), RPC_TASK_ASYNC, &nfs_unlink_ops, data);
+       if (!IS_ERR(task))
+               rpc_put_task(task);
+       return 1;
+}
+
+static int nfs_call_unlink(struct dentry *dentry, struct nfs_unlinkdata *data)
+{
        struct dentry *parent;
        struct inode *dir;
+       int ret = 0;
 
-       if (nfs_copy_dname(dentry, data) < 0)
-               goto out_free;
 
        parent = dget_parent(dentry);
        if (parent == NULL)
                goto out_free;
-       dir = igrab(parent->d_inode);
+       dir = parent->d_inode;
+       if (nfs_copy_dname(dentry, data) == 0)
+               goto out_dput;
+       /* Non-exclusive lock protects against concurrent lookup() calls */
+       spin_lock(&dir->i_lock);
+       if (atomic_inc_not_zero(&NFS_I(dir)->silly_count) == 0) {
+               /* Deferred delete */
+               hlist_add_head(&data->list, &NFS_I(dir)->silly_list);
+               spin_unlock(&dir->i_lock);
+               ret = 1;
+               goto out_dput;
+       }
+       spin_unlock(&dir->i_lock);
+       ret = nfs_do_call_unlink(parent, dir, data);
+out_dput:
        dput(parent);
-       if (dir == NULL)
-               goto out_free;
+out_free:
+       return ret;
+}
 
-       data->dir = dir;
-       data->args.fh = NFS_FH(dir);
-       nfs_fattr_init(&data->res.dir_attr);
+void nfs_block_sillyrename(struct dentry *dentry)
+{
+       struct nfs_inode *nfsi = NFS_I(dentry->d_inode);
 
-       task = rpc_run_task(NFS_CLIENT(dir), RPC_TASK_ASYNC, &nfs_unlink_ops, data);
-       if (!IS_ERR(task))
-               rpc_put_task(task);
-       return 1;
-out_free:
-       return 0;
+       wait_event(nfsi->waitqueue, atomic_cmpxchg(&nfsi->silly_count, 1, 0) == 1);
+}
+
+void nfs_unblock_sillyrename(struct dentry *dentry)
+{
+       struct inode *dir = dentry->d_inode;
+       struct nfs_inode *nfsi = NFS_I(dir);
+       struct nfs_unlinkdata *data;
+
+       atomic_inc(&nfsi->silly_count);
+       spin_lock(&dir->i_lock);
+       while (!hlist_empty(&nfsi->silly_list)) {
+               if (!atomic_inc_not_zero(&nfsi->silly_count))
+                       break;
+               data = hlist_entry(nfsi->silly_list.first, struct nfs_unlinkdata, list);
+               hlist_del(&data->list);
+               spin_unlock(&dir->i_lock);
+               if (nfs_do_call_unlink(dentry, dir, data) == 0)
+                       nfs_free_unlinkdata(data);
+               spin_lock(&dir->i_lock);
+       }
+       spin_unlock(&dir->i_lock);
 }
 
 /**

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index c5164c257f71aa17ec51dda414a1921053d8ac5d..e82a6ebc725d7b18a76fdccc9d58853b42a8bdba 100644 (file)
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -160,6 +160,12 @@ struct nfs_inode {
        /* Open contexts for shared mmap writes */
        struct list_head        open_files;
 
+       /* Number of in-flight sillydelete RPC calls */
+       atomic_t                silly_count;
+       /* List of deferred sillydelete requests */
+       struct hlist_head       silly_list;
+       wait_queue_head_t       waitqueue;
+
 #ifdef CONFIG_NFS_V4
        struct nfs4_cached_acl  *nfs4_acl;
         /* NFSv4 state */
@@ -394,6 +400,8 @@ extern void nfs_release_automount_timer(void);
  */
 extern int  nfs_async_unlink(struct inode *dir, struct dentry *dentry);
 extern void nfs_complete_unlink(struct dentry *dentry, struct inode *);
+extern void nfs_block_sillyrename(struct dentry *dentry);
+extern void nfs_unblock_sillyrename(struct dentry *dentry);
 
 /*
  * linux/fs/nfs/write.c