[CIFS] Provide sane values for nlink

Since we don't get info about the number of links from the readdir
linfo levels, stat() will return 0 for st_nlink, and in particular,
samba re-exported shares will show directories as files (as samba is
keying off st_nlink before evaluating how to set the dos modebits)
when doing a dir or ls.

Copy nlink to the inode, unless it wasn't provided.  Provide
sane values if we don't have an existing one and none was provided.

Signed-off-by: Jim McDonough <jmcd@samba.org>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: David Disseldorp <ddiss@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

3 files changed, 43 insertions, 6 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 9c72be6fb0df..52b6f6c26bfc 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1268,6 +1268,7 @@ struct dfs_info3_param {
 #define CIFS_FATTR_DELETE_PENDING       0x2
 #define CIFS_FATTR_NEED_REVAL           0x4
 #define CIFS_FATTR_INO_COLLISION        0x8
+#define CIFS_FATTR_UNKNOWN_NLINK        0x10
 
 struct cifs_fattr {
         u32             cf_flags;
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index f9ff9c173f78..867b7cdc794a 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -120,6 +120,33 @@ cifs_revalidate_cache(struct inode *inode, struct cifs_fattr *fattr)
         cifs_i->invalid_mapping = true;
 }
 
+/*
+ * copy nlink to the inode, unless it wasn't provided.  Provide
+ * sane values if we don't have an existing one and none was provided
+ */
+static void
+cifs_nlink_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
+{
+        /*
+         * if we're in a situation where we can't trust what we
+         * got from the server (readdir, some non-unix cases)
+         * fake reasonable values
+         */
+        if (fattr->cf_flags & CIFS_FATTR_UNKNOWN_NLINK) {
+                /* only provide fake values on a new inode */
+                if (inode->i_state & I_NEW) {
+                        if (fattr->cf_cifsattrs & ATTR_DIRECTORY)
+                                set_nlink(inode, 2);
+                        else
+                                set_nlink(inode, 1);
+                }
+                return;
+        }
+
+        /* we trust the server, so update it */
+        set_nlink(inode, fattr->cf_nlink);
+}
+
 /* populate an inode with info from a cifs_fattr struct */
 void
 cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
@@ -134,7 +161,7 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
         inode->i_mtime = fattr->cf_mtime;
         inode->i_ctime = fattr->cf_ctime;
         inode->i_rdev = fattr->cf_rdev;
-        set_nlink(inode, fattr->cf_nlink);
+        cifs_nlink_fattr_to_inode(inode, fattr);
         inode->i_uid = fattr->cf_uid;
         inode->i_gid = fattr->cf_gid;
 
@@ -541,6 +568,7 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
         fattr->cf_bytes = le64_to_cpu(info->AllocationSize);
         fattr->cf_createtime = le64_to_cpu(info->CreationTime);
 
+        fattr->cf_nlink = le32_to_cpu(info->NumberOfLinks);
         if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
                 fattr->cf_mode = S_IFDIR | cifs_sb->mnt_dir_mode;
                 fattr->cf_dtype = DT_DIR;
@@ -548,7 +576,8 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
                  * Server can return wrong NumberOfLinks value for directories
                  * when Unix extensions are disabled - fake it.
                  */
-                fattr->cf_nlink = 2;
+                if (!tcon->unix_ext)
+                        fattr->cf_flags |= CIFS_FATTR_UNKNOWN_NLINK;
         } else if (fattr->cf_cifsattrs & ATTR_REPARSE) {
                 fattr->cf_mode = S_IFLNK;
                 fattr->cf_dtype = DT_LNK;
@@ -561,11 +590,15 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
                 if (fattr->cf_cifsattrs & ATTR_READONLY)
                         fattr->cf_mode &= ~(S_IWUGO);
 
-                fattr->cf_nlink = le32_to_cpu(info->NumberOfLinks);
-                if (fattr->cf_nlink < 1) {
-                        cifs_dbg(1, "replacing bogus file nlink value %u\n",
+                /*
+                 * Don't accept zero nlink from non-unix servers unless
+                 * delete is pending.  Instead mark it as unknown.
+                 */
+                if ((fattr->cf_nlink < 1) && !tcon->unix_ext &&
+                    !info->DeletePending) {
+                        cifs_dbg(1, "bogus file nlink value %u\n",
                                 fattr->cf_nlink);
-                        fattr->cf_nlink = 1;
+                        fattr->cf_flags |= CIFS_FATTR_UNKNOWN_NLINK;
                 }
         }
 
diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index 42ef03be089f..53a75f3d0179 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -180,6 +180,9 @@ cifs_fill_common_info(struct cifs_fattr *fattr, struct cifs_sb_info *cifs_sb)
                 fattr->cf_dtype = DT_REG;
         }
 
+        /* non-unix readdir doesn't provide nlink */
+        fattr->cf_flags |= CIFS_FATTR_UNKNOWN_NLINK;
+
         if (fattr->cf_cifsattrs & ATTR_READONLY)
                 fattr->cf_mode &= ~S_IWUGO;