Signed-off-by: Aurelien Aptel <aaptel@xxxxxxxx>
---
fs/cifs/connect.c | 32 +++++++++++++++++++++++++++++++-
1 file changed, 31 insertions(+), 1 deletion(-)
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 8b5e401f547a..ff7a653fd322 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2704,6 +2704,13 @@ cifs_set_cifscreds(struct smb_vol *vol __attribute__((unused)),
}
#endif /* CONFIG_KEYS */
+/**
+ * cifs_get_smb_ses - get a session matching @volume_info data from @server
+ *
+ * This function assumes it is being called from cifs_mount() where we
+ * already got a server reference (server refcount +1). See
+ * cifs_get_tcon() for refcount explanations.
+ */
static struct cifs_ses *
cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
{
@@ -2877,6 +2884,26 @@ cifs_put_tcon(struct cifs_tcon *tcon)
cifs_put_smb_ses(ses);
}
+/**
+ * cifs_get_tcon - get a tcon matching @volume_info data from @ses
+ *
+ * - tcon refcount is the number of mount points using the tcon.
+ * - ses refcount is the number of tcon using the session.
+ *
+ * 1. This function assumes it is being called from cifs_mount() where
+ * we already got a session reference (ses refcount +1).
+ *
+ * 2. Since we're in the context of adding a mount point, the end
+ * result should be either:
+ *
+ * a) a new tcon already allocated with refcount=1 (1 mount point) and
+ * its session refcount incremented (1 new tcon). This +1 was
+ * already done in (1).
+ *
+ * b) an existing tcon with refcount+1 (add a mount point to it) and
+ * identical ses refcount (no new tcon). Because of (1) we need to
+ * decrement the ses refcount.
+ */
static struct cifs_tcon *
cifs_get_tcon(struct cifs_ses *ses, struct smb_vol *volume_info)
{
@@ -2885,8 +2912,11 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb_vol *volume_info)
tcon = cifs_find_tcon(ses, volume_info);
if (tcon) {
+ /*
+ * tcon has refcount already incremented but we need to
+ * decrement extra ses reference gotten by caller (case b)
+ */
cifs_dbg(FYI, "Found match on UNC path\n");
- /* existing tcon already has a reference */
cifs_put_smb_ses(ses);
return tcon;
}
--
2.12.3
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