[PATCH AUTOSEL 4.20 66/77] CIFS: Fix mounts if the client is low on credits

Sasha Levin
2019-02-15T02:36:24Z

From: Pavel Shilovsky <pshilov@microsoft.com>

[ 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>
---
fs/cifs/smb2inode.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)

diff --git a/fs/cifs/smb2inode.c b/fs/cifs/smb2inode.c
index a8999f930b22..057d2034209f 100644
--- 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;

--
2.19.1