locks: break delegations on any attribute modification

NFSv4 uses leases to guarantee that clients can cache metadata as well
as data.

Cc: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: David Howells <dhowells@redhat.com>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Dustin Kirkland <dustin.kirkland@gazzang.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

10 files changed, 69 insertions, 17 deletions

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 1b8490e2fbde..0f3820121e02 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -216,7 +216,7 @@ static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
                 newattrs.ia_gid = gid;
                 newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID;
                 mutex_lock(&dentry->d_inode->i_mutex);
-                notify_change(dentry, &newattrs);
+                notify_change(dentry, &newattrs, NULL);
                 mutex_unlock(&dentry->d_inode->i_mutex);
 
                 /* mark as kernel-created inode */
@@ -322,7 +322,7 @@ static int handle_remove(const char *nodename, struct device *dev)
                         newattrs.ia_valid =
                                 ATTR_UID|ATTR_GID|ATTR_MODE;
                         mutex_lock(&dentry->d_inode->i_mutex);
-                        notify_change(dentry, &newattrs);
+                        notify_change(dentry, &newattrs, NULL);
                         mutex_unlock(&dentry->d_inode->i_mutex);
                         err = vfs_unlink(parent.dentry->d_inode, dentry, NULL);
                         if (!err || err == -ENOENT)
diff --git a/fs/attr.c b/fs/attr.c
index 1449adb14ef6..267968d94673 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -167,7 +167,27 @@ void setattr_copy(struct inode *inode, const struct iattr *attr)
 }
 EXPORT_SYMBOL(setattr_copy);
 
-int notify_change(struct dentry * dentry, struct iattr * attr)
+/**
+ * notify_change - modify attributes of a filesytem object
+ * @dentry:     object affected
+ * @iattr:      new attributes
+ * @delegated_inode: returns inode, if the inode is delegated
+ *
+ * The caller must hold the i_mutex on the affected object.
+ *
+ * If notify_change discovers a delegation in need of breaking,
+ * it will return -EWOULDBLOCK and return a reference to the inode in
+ * delegated_inode.  The caller should then break the delegation and
+ * retry.  Because breaking a delegation may take a long time, the
+ * caller should drop the i_mutex before doing so.
+ *
+ * Alternatively, a caller may pass NULL for delegated_inode.  This may
+ * be appropriate for callers that expect the underlying filesystem not
+ * to be NFS exported.  Also, passing NULL is fine for callers holding
+ * the file open for write, as there can be no conflicting delegation in
+ * that case.
+ */
+int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
 {
         struct inode *inode = dentry->d_inode;
         umode_t mode = inode->i_mode;
@@ -243,6 +263,9 @@ int notify_change(struct dentry * dentry, struct iattr * attr)
         error = security_inode_setattr(dentry, attr);
         if (error)
                 return error;
+        error = try_break_deleg(inode, delegated_inode);
+        if (error)
+                return error;
 
         if (inode->i_op->setattr)
                 error = inode->i_op->setattr(dentry, attr);
diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index 43eb5592cdea..5088a418ac4d 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -449,14 +449,14 @@ static int cachefiles_attr_changed(struct fscache_object *_object)
                 _debug("discard tail %llx", oi_size);
                 newattrs.ia_valid = ATTR_SIZE;
                 newattrs.ia_size = oi_size & PAGE_MASK;
-                ret = notify_change(object->backer, &newattrs);
+                ret = notify_change(object->backer, &newattrs, NULL);
                 if (ret < 0)
                         goto truncate_failed;
         }
 
         newattrs.ia_valid = ATTR_SIZE;
         newattrs.ia_size = ni_size;
-        ret = notify_change(object->backer, &newattrs);
+        ret = notify_change(object->backer, &newattrs, NULL);
 
 truncate_failed:
         mutex_unlock(&object->backer->d_inode->i_mutex);
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 1c628f023041..c36c44824471 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -882,7 +882,7 @@ int ecryptfs_truncate(struct dentry *dentry, loff_t new_length)
                 struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
 
                 mutex_lock(&lower_dentry->d_inode->i_mutex);
-                rc = notify_change(lower_dentry, &lower_ia);
+                rc = notify_change(lower_dentry, &lower_ia, NULL);
                 mutex_unlock(&lower_dentry->d_inode->i_mutex);
         }
         return rc;
@@ -983,7 +983,7 @@ static int ecryptfs_setattr(struct dentry *dentry, struct iattr *ia)
                 lower_ia.ia_valid &= ~ATTR_MODE;
 
         mutex_lock(&lower_dentry->d_inode->i_mutex);
-        rc = notify_change(lower_dentry, &lower_ia);
+        rc = notify_change(lower_dentry, &lower_ia, NULL);
         mutex_unlock(&lower_dentry->d_inode->i_mutex);
 out:
         fsstack_copy_attr_all(inode, lower_inode);
diff --git a/fs/hpfs/namei.c b/fs/hpfs/namei.c
index 345713d2f8f3..1b39afdd86fd 100644
--- a/fs/hpfs/namei.c
+++ b/fs/hpfs/namei.c
@@ -407,7 +407,7 @@ again:
                         /*printk("HPFS: truncating file before delete.\n");*/
                         newattrs.ia_size = 0;
                         newattrs.ia_valid = ATTR_SIZE | ATTR_CTIME;
-                        err = notify_change(dentry, &newattrs);
+                        err = notify_change(dentry, &newattrs, NULL);
                         put_write_access(inode);
                         if (!err)
                                 goto again;
diff --git a/fs/inode.c b/fs/inode.c
index ce48c359ce9e..4bcdad3c9361 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1603,7 +1603,11 @@ static int __remove_suid(struct dentry *dentry, int kill)
         struct iattr newattrs;
 
         newattrs.ia_valid = ATTR_FORCE | kill;
-        return notify_change(dentry, &newattrs);
+        /*
+         * Note we call this on write, so notify_change will not
+         * encounter any conflicting delegations:
+         */
+        return notify_change(dentry, &newattrs, NULL);
 }
 
 int file_remove_suid(struct file *file)
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 27ba21b5f383..94b5f5d2bfed 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -427,7 +427,7 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
                         goto out_nfserr;
                 fh_lock(fhp);
 
-                host_err = notify_change(dentry, iap);
+                host_err = notify_change(dentry, iap, NULL);
                 err = nfserrno(host_err);
                 fh_unlock(fhp);
         }
@@ -988,7 +988,11 @@ static void kill_suid(struct dentry *dentry)
         ia.ia_valid = ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 
         mutex_lock(&dentry->d_inode->i_mutex);
-        notify_change(dentry, &ia);
+        /*
+         * Note we call this on write, so notify_change will not
+         * encounter any conflicting delegations:
+         */
+        notify_change(dentry, &ia, NULL);
         mutex_unlock(&dentry->d_inode->i_mutex);
 }
 
diff --git a/fs/open.c b/fs/open.c
index fffbed40dbe9..4b3e1edf2fe4 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -57,7 +57,8 @@ int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
                 newattrs.ia_valid |= ret | ATTR_FORCE;
 
         mutex_lock(&dentry->d_inode->i_mutex);
-        ret = notify_change(dentry, &newattrs);
+        /* Note any delegations or leases have already been broken: */
+        ret = notify_change(dentry, &newattrs, NULL);
         mutex_unlock(&dentry->d_inode->i_mutex);
         return ret;
 }
@@ -464,21 +465,28 @@ out:
 static int chmod_common(struct path *path, umode_t mode)
 {
         struct inode *inode = path->dentry->d_inode;
+        struct inode *delegated_inode = NULL;
         struct iattr newattrs;
         int error;
 
         error = mnt_want_write(path->mnt);
         if (error)
                 return error;
+retry_deleg:
         mutex_lock(&inode->i_mutex);
         error = security_path_chmod(path, mode);
         if (error)
                 goto out_unlock;
         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
-        error = notify_change(path->dentry, &newattrs);
+        error = notify_change(path->dentry, &newattrs, &delegated_inode);
 out_unlock:
         mutex_unlock(&inode->i_mutex);
+        if (delegated_inode) {
+                error = break_deleg_wait(&delegated_inode);
+                if (!error)
+                        goto retry_deleg;
+        }
         mnt_drop_write(path->mnt);
         return error;
 }
@@ -522,6 +530,7 @@ SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 static int chown_common(struct path *path, uid_t user, gid_t group)
 {
         struct inode *inode = path->dentry->d_inode;
+        struct inode *delegated_inode = NULL;
         int error;
         struct iattr newattrs;
         kuid_t uid;
@@ -546,12 +555,17 @@ static int chown_common(struct path *path, uid_t user, gid_t group)
         if (!S_ISDIR(inode->i_mode))
                 newattrs.ia_valid |=
                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
+retry_deleg:
         mutex_lock(&inode->i_mutex);
         error = security_path_chown(path, uid, gid);
         if (!error)
-                error = notify_change(path->dentry, &newattrs);
+                error = notify_change(path->dentry, &newattrs, &delegated_inode);
         mutex_unlock(&inode->i_mutex);
-
+        if (delegated_inode) {
+                error = break_deleg_wait(&delegated_inode);
+                if (!error)
+                        goto retry_deleg;
+        }
         return error;
 }
 
diff --git a/fs/utimes.c b/fs/utimes.c
index f4fb7eca10e8..aa138d64560a 100644
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -53,6 +53,7 @@ static int utimes_common(struct path *path, struct timespec *times)
         int error;
         struct iattr newattrs;
         struct inode *inode = path->dentry->d_inode;
+        struct inode *delegated_inode = NULL;
 
         error = mnt_want_write(path->mnt);
         if (error)
@@ -101,9 +102,15 @@ static int utimes_common(struct path *path, struct timespec *times)
                                 goto mnt_drop_write_and_out;
                 }
         }
+retry_deleg:
         mutex_lock(&inode->i_mutex);
-        error = notify_change(path->dentry, &newattrs);
+        error = notify_change(path->dentry, &newattrs, &delegated_inode);
         mutex_unlock(&inode->i_mutex);
+        if (delegated_inode) {
+                error = break_deleg_wait(&delegated_inode);
+                if (!error)
+                        goto retry_deleg;
+        }
 
 mnt_drop_write_and_out:
         mnt_drop_write(path->mnt);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6e36e7118ec1..ab2a0ca82dc5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2278,7 +2278,7 @@ extern void emergency_remount(void);
 #ifdef CONFIG_BLOCK
 extern sector_t bmap(struct inode *, sector_t);
 #endif
-extern int notify_change(struct dentry *, struct iattr *);
+extern int notify_change(struct dentry *, struct iattr *, struct inode **);
 extern int inode_permission(struct inode *, int);
 extern int generic_permission(struct inode *, int);