[PATCH v6.9-rc1 01/10] dlm: fix user space lock decision to copy lvb

[Alexander Aring <aahringo@redhat.com>]

This patch fixes the copy lvb decision in case of user space DLM lock
requests. Currently the granted mode and requested mode is the same when
evaluating the dlm_lvb_operations matrix. That reflects the diagonal of
the dlm_lvb_operations matrix. Luckely it will mostly return a non zero
result on its diagonal, but in case of requested mode PW or EX the
diagonal returns 0, depending on the granted mode before the user might
get an invalid lvb data that is marked as valid.

This patch will move the decision if the lvb area should be copied or
not to the enqueue callback functionality because the granted mode is
known there. It also removes any lkb reference in the user callback
result delivery functionality that is required for a future fix.

Fixes: 61bed0baa4db ("fs: dlm: use a non-static queue for callbacks")
Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/ast.c          | 14 ++++++++++++++
 fs/dlm/dlm_internal.h |  1 +
 fs/dlm/user.c         | 15 ++-------------
 3 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/fs/dlm/ast.c b/fs/dlm/ast.c
index 1f2f70a1b824..decedc4ee15f 100644
--- a/fs/dlm/ast.c
+++ b/fs/dlm/ast.c
@@ -12,6 +12,7 @@
 #include <trace/events/dlm.h>
 
 #include "dlm_internal.h"
+#include "lvb_table.h"
 #include "memory.h"
 #include "lock.h"
 #include "user.h"
@@ -42,6 +43,7 @@ int dlm_enqueue_lkb_callback(struct dlm_lkb *lkb, uint32_t flags, int mode,
 	struct dlm_ls *ls = lkb->lkb_resource->res_ls;
 	int rv = DLM_ENQUEUE_CALLBACK_SUCCESS;
 	struct dlm_callback *cb;
+	int copy_lvb = 0;
 	int prev_mode;
 
 	if (flags & DLM_CB_BAST) {
@@ -73,6 +75,17 @@ int dlm_enqueue_lkb_callback(struct dlm_lkb *lkb, uint32_t flags, int mode,
 				goto out;
 			}
 		}
+	} else if (flags & DLM_CB_CAST) {
+		if (test_bit(DLM_DFL_USER_BIT, &lkb->lkb_dflags)) {
+			if (lkb->lkb_last_cast)
+				prev_mode = lkb->lkb_last_cb->mode;
+			else
+				prev_mode = -1;
+
+			if (!status && lkb->lkb_lksb->sb_lvbptr &&
+			    dlm_lvb_operations[prev_mode + 1][mode + 1])
+				copy_lvb = 1;
+		}
 	}
 
 	cb = dlm_allocate_cb();
@@ -85,6 +98,7 @@ int dlm_enqueue_lkb_callback(struct dlm_lkb *lkb, uint32_t flags, int mode,
 	cb->mode = mode;
 	cb->sb_status = status;
 	cb->sb_flags = (sbflags & 0x000000FF);
+	cb->copy_lvb = copy_lvb;
 	kref_init(&cb->ref);
 	if (!test_and_set_bit(DLM_IFL_CB_PENDING_BIT, &lkb->lkb_iflags))
 		rv = DLM_ENQUEUE_CALLBACK_NEED_SCHED;
diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h
index 3b4dbce849f0..a9137c90f348 100644
--- a/fs/dlm/dlm_internal.h
+++ b/fs/dlm/dlm_internal.h
@@ -222,6 +222,7 @@ struct dlm_callback {
 	int			sb_status;	/* copy to lksb status */
 	uint8_t			sb_flags;	/* copy to lksb flags */
 	int8_t			mode; /* rq mode of bast, gr mode of cast */
+	int			copy_lvb;
 
 	struct list_head	list;
 	struct kref		ref;
diff --git a/fs/dlm/user.c b/fs/dlm/user.c
index 9f9b68448830..12a483deeef5 100644
--- a/fs/dlm/user.c
+++ b/fs/dlm/user.c
@@ -21,7 +21,6 @@
 #include "dlm_internal.h"
 #include "lockspace.h"
 #include "lock.h"
-#include "lvb_table.h"
 #include "user.h"
 #include "ast.h"
 #include "config.h"
@@ -806,8 +805,7 @@ static ssize_t device_read(struct file *file, char __user *buf, size_t count,
 	struct dlm_lkb *lkb;
 	DECLARE_WAITQUEUE(wait, current);
 	struct dlm_callback *cb;
-	int rv, ret, copy_lvb = 0;
-	int old_mode, new_mode;
+	int rv, ret;
 
 	if (count == sizeof(struct dlm_device_version)) {
 		rv = copy_version_to_user(buf, count);
@@ -864,9 +862,6 @@ static ssize_t device_read(struct file *file, char __user *buf, size_t count,
 
 	lkb = list_first_entry(&proc->asts, struct dlm_lkb, lkb_cb_list);
 
-	/* rem_lkb_callback sets a new lkb_last_cast */
-	old_mode = lkb->lkb_last_cast->mode;
-
 	rv = dlm_dequeue_lkb_callback(lkb, &cb);
 	switch (rv) {
 	case DLM_DEQUEUE_CALLBACK_EMPTY:
@@ -895,12 +890,6 @@ static ssize_t device_read(struct file *file, char __user *buf, size_t count,
 	if (cb->flags & DLM_CB_BAST) {
 		trace_dlm_bast(lkb->lkb_resource->res_ls, lkb, cb->mode);
 	} else if (cb->flags & DLM_CB_CAST) {
-		new_mode = cb->mode;
-
-		if (!cb->sb_status && lkb->lkb_lksb->sb_lvbptr &&
-		    dlm_lvb_operations[old_mode + 1][new_mode + 1])
-			copy_lvb = 1;
-
 		lkb->lkb_lksb->sb_status = cb->sb_status;
 		lkb->lkb_lksb->sb_flags = cb->sb_flags;
 		trace_dlm_ast(lkb->lkb_resource->res_ls, lkb);
@@ -908,7 +897,7 @@ static ssize_t device_read(struct file *file, char __user *buf, size_t count,
 
 	ret = copy_result_to_user(lkb->lkb_ua,
 				  test_bit(DLM_PROC_FLAGS_COMPAT, &proc->flags),
-				  cb->flags, cb->mode, copy_lvb, buf, count);
+				  cb->flags, cb->mode, cb->copy_lvb, buf, count);
 
 	kref_put(&cb->ref, dlm_release_callback);
 
-- 
2.43.0