NFS: Avoid flushing data while holding directory locks in nfs_rename()

The Linux client assumes that all filehandles are non-volatile for
renames within the same directory (otherwise sillyrename cannot work).
However, the existence of the Linux 'subtree_check' export option has
meant that nfs_rename() has always assumed it needs to flush writes
before attempting to rename.

Since NFSv4 does allow the client to query whether or not the server
exhibits this behaviour, and since knfsd does actually set the
appropriate flag when 'subtree_check' is enabled on an export, it
should be OK to optimise away the write flushing behaviour in the cases
where it is clearly not needed.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 2115c1189c2df1f483c48b45b4c8b446b58e29f7..6d63b958c4bb1323cd6917412528720468876eac 100644 (file)
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -1105,6 +1105,8 @@ struct nfs_server *nfs_create_server(struct fs_context *fc)
                if (server->namelen == 0 || server->namelen > NFS2_MAXNAMLEN)
                        server->namelen = NFS2_MAXNAMLEN;
        }
+       /* Linux 'subtree_check' borkenness mandates this setting */
+       server->fh_expire_type = NFS_FH_VOL_RENAME;
 
        if (!(fattr->valid & NFS_ATTR_FATTR)) {
                error = ctx->nfs_mod->rpc_ops->getattr(server, ctx->mntfh,

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index bd23fc736b3947f25da03c1063dc3d2d882547e7..d0e0b435a84316af274dcf2505d996f2d1e3b270 100644 (file)
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -2676,6 +2676,18 @@ nfs_unblock_rename(struct rpc_task *task, struct nfs_renamedata *data)
        unblock_revalidate(new_dentry);
 }
 
+static bool nfs_rename_is_unsafe_cross_dir(struct dentry *old_dentry,
+                                          struct dentry *new_dentry)
+{
+       struct nfs_server *server = NFS_SB(old_dentry->d_sb);
+
+       if (old_dentry->d_parent != new_dentry->d_parent)
+               return false;
+       if (server->fh_expire_type & NFS_FH_RENAME_UNSAFE)
+               return !(server->fh_expire_type & NFS_FH_NOEXPIRE_WITH_OPEN);
+       return true;
+}
+
 /*
  * RENAME
  * FIXME: Some nfsds, like the Linux user space nfsd, may generate a
@@ -2763,7 +2775,8 @@ int nfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 
        }
 
-       if (S_ISREG(old_inode->i_mode))
+       if (S_ISREG(old_inode->i_mode) &&
+           nfs_rename_is_unsafe_cross_dir(old_dentry, new_dentry))
                nfs_sync_inode(old_inode);
        task = nfs_async_rename(old_dir, new_dir, old_dentry, new_dentry,
                                must_unblock ? nfs_unblock_rename : NULL);

diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 71319637a84e61c848a296910109828c2c245d67..ee03f3cef30ca5fa3295cb5ed7b0970a71b42d33 100644 (file)
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -213,6 +213,15 @@ struct nfs_server {
        char                    *fscache_uniq;  /* Uniquifier (or NULL) */
 #endif
 
+       /* The following #defines numerically match the NFSv4 equivalents */
+#define NFS_FH_NOEXPIRE_WITH_OPEN (0x1)
+#define NFS_FH_VOLATILE_ANY (0x2)
+#define NFS_FH_VOL_MIGRATION (0x4)
+#define NFS_FH_VOL_RENAME (0x8)
+#define NFS_FH_RENAME_UNSAFE (NFS_FH_VOLATILE_ANY | NFS_FH_VOL_RENAME)
+       u32                     fh_expire_type; /* V4 bitmask representing file
+                                                  handle volatility type for
+                                                  this filesystem */
        u32                     pnfs_blksize;   /* layout_blksize attr */
 #if IS_ENABLED(CONFIG_NFS_V4)
        u32                     attr_bitmask[3];/* V4 bitmask representing the set
@@ -236,9 +245,6 @@ struct nfs_server {
        u32                     acl_bitmask;    /* V4 bitmask representing the ACEs
                                                   that are supported on this
                                                   filesystem */
-       u32                     fh_expire_type; /* V4 bitmask representing file
-                                                  handle volatility type for
-                                                  this filesystem */
        struct pnfs_layoutdriver_type  *pnfs_curr_ld; /* Active layout driver */
        struct rpc_wait_queue   roc_rpcwaitq;
        void                    *pnfs_ld_data;  /* per mount point data */