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Subject[PATCH 4.18 009/123] cifs: use a refcount to protect open/closing the cached file handle
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ronnie Sahlberg <lsahlber@redhat.com>

commit 9da6ec7775d2cd76df53fbf4f1f35f6d490204f5 upstream.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/cifs/cifsglob.h | 1 +
fs/cifs/smb2inode.c | 4 +++-
fs/cifs/smb2ops.c | 31 ++++++++++++++++++++++++++-----
fs/cifs/smb2proto.h | 1 +
4 files changed, 31 insertions(+), 6 deletions(-)

--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -913,6 +913,7 @@ cap_unix(struct cifs_ses *ses)

struct cached_fid {
bool is_valid:1; /* Do we have a useable root fid */
+ struct kref refcount;
struct cifs_fid *fid;
struct mutex fid_mutex;
struct cifs_tcon *tcon;
--- a/fs/cifs/smb2inode.c
+++ b/fs/cifs/smb2inode.c
@@ -120,7 +120,9 @@ smb2_open_op_close(const unsigned int xi
break;
}

- if (use_cached_root_handle == false)
+ if (use_cached_root_handle)
+ close_shroot(&tcon->crfid);
+ else
rc = SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
if (tmprc)
rc = tmprc;
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -466,21 +466,36 @@ out:
return rc;
}

-void
-smb2_cached_lease_break(struct work_struct *work)
+static void
+smb2_close_cached_fid(struct kref *ref)
{
- struct cached_fid *cfid = container_of(work,
- struct cached_fid, lease_break);
- mutex_lock(&cfid->fid_mutex);
+ struct cached_fid *cfid = container_of(ref, struct cached_fid,
+ refcount);
+
if (cfid->is_valid) {
cifs_dbg(FYI, "clear cached root file handle\n");
SMB2_close(0, cfid->tcon, cfid->fid->persistent_fid,
cfid->fid->volatile_fid);
cfid->is_valid = false;
}
+}
+
+void close_shroot(struct cached_fid *cfid)
+{
+ mutex_lock(&cfid->fid_mutex);
+ kref_put(&cfid->refcount, smb2_close_cached_fid);
mutex_unlock(&cfid->fid_mutex);
}

+void
+smb2_cached_lease_break(struct work_struct *work)
+{
+ struct cached_fid *cfid = container_of(work,
+ struct cached_fid, lease_break);
+
+ close_shroot(cfid);
+}
+
/*
* Open the directory at the root of a share
*/
@@ -495,6 +510,7 @@ int open_shroot(unsigned int xid, struct
if (tcon->crfid.is_valid) {
cifs_dbg(FYI, "found a cached root file handle\n");
memcpy(pfid, tcon->crfid.fid, sizeof(struct cifs_fid));
+ kref_get(&tcon->crfid.refcount);
mutex_unlock(&tcon->crfid.fid_mutex);
return 0;
}
@@ -511,6 +527,8 @@ int open_shroot(unsigned int xid, struct
memcpy(tcon->crfid.fid, pfid, sizeof(struct cifs_fid));
tcon->crfid.tcon = tcon;
tcon->crfid.is_valid = true;
+ kref_init(&tcon->crfid.refcount);
+ kref_get(&tcon->crfid.refcount);
}
mutex_unlock(&tcon->crfid.fid_mutex);
return rc;
@@ -552,6 +570,9 @@ smb3_qfs_tcon(const unsigned int xid, st
FS_SECTOR_SIZE_INFORMATION); /* SMB3 specific */
if (no_cached_open)
SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
+ else
+ close_shroot(&tcon->crfid);
+
return;
}

--- a/fs/cifs/smb2proto.h
+++ b/fs/cifs/smb2proto.h
@@ -68,6 +68,7 @@ extern int smb3_handle_read_data(struct

extern int open_shroot(unsigned int xid, struct cifs_tcon *tcon,
struct cifs_fid *pfid);
+extern void close_shroot(struct cached_fid *cfid);
extern void move_smb2_info_to_cifs(FILE_ALL_INFO *dst,
struct smb2_file_all_info *src);
extern int smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,

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