CIFS: Fix mounts if the client is low on credits

[ Upstream commit 6a9cbdd1ceca1dc2359ddf082efe61b97c3e752b ]

If the server doesn't grant us at least 3 credits during the mount
we won't be able to complete it because query path info operation
requires 3 credits. Use the cached file handle if possible to allow
the mount to succeed.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/cifs/smb2inode.c b/fs/cifs/smb2inode.c
index a8999f930b224ec6d6af2d74479270a43a000f56..057d2034209fa18b7e2d5446ed18f6040fad859a 100644 (file)
--- a/fs/cifs/smb2inode.c
+++ b/fs/cifs/smb2inode.c
@@ -294,6 +294,8 @@ smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
        int rc;
        struct smb2_file_all_info *smb2_data;
        __u32 create_options = 0;
+       struct cifs_fid fid;
+       bool no_cached_open = tcon->nohandlecache;
 
        *adjust_tz = false;
        *symlink = false;
@@ -302,6 +304,21 @@ smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
                            GFP_KERNEL);
        if (smb2_data == NULL)
                return -ENOMEM;
+
+       /* If it is a root and its handle is cached then use it */
+       if (!strlen(full_path) && !no_cached_open) {
+               rc = open_shroot(xid, tcon, &fid);
+               if (rc)
+                       goto out;
+               rc = SMB2_query_info(xid, tcon, fid.persistent_fid,
+                                    fid.volatile_fid, smb2_data);
+               close_shroot(&tcon->crfid);
+               if (rc)
+                       goto out;
+               move_smb2_info_to_cifs(data, smb2_data);
+               goto out;
+       }
+
        if (backup_cred(cifs_sb))
                create_options |= CREATE_OPEN_BACKUP_INTENT;