[PATCH 5.10 038/236] s390/debug: fix debug area life cycle

Greg Kroah-Hartman
2021-09-13T13:37:54Z

From: Peter Oberparleiter <oberpar@linux.ibm.com>

[ Upstream commit 9372a82892c2caa6bccab9a4081166fa769699f8 ]

Currently allocation and registration of s390dbf debug areas are tied
together. As a result, a debug area cannot be unregistered and
re-registered while any process has an associated debugfs file open.

Fix this by splitting alloc/release from register/unregister.

Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/kernel/debug.c | 102 +++++++++++++++++++++------------------
1 file changed, 56 insertions(+), 46 deletions(-)

diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c
index e392d3e42b1d..89fbfb3b1e01 100644
--- a/arch/s390/kernel/debug.c
+++ b/arch/s390/kernel/debug.c
@@ -314,24 +314,6 @@ static debug_info_t *debug_info_create(const char *name, int pages_per_area,
goto out;

rc->mode = mode & ~S_IFMT;
-
- /* create root directory */
- rc->debugfs_root_entry = debugfs_create_dir(rc->name,
- debug_debugfs_root_entry);
-
- /* append new element to linked list */
- if (!debug_area_first) {
- /* first element in list */
- debug_area_first = rc;
- rc->prev = NULL;
- } else {
- /* append element to end of list */
- debug_area_last->next = rc;
- rc->prev = debug_area_last;
- }
- debug_area_last = rc;
- rc->next = NULL;
-
refcount_set(&rc->ref_count, 1);
out:
return rc;
@@ -391,27 +373,10 @@ static void debug_info_get(debug_info_t *db_info)
*/
static void debug_info_put(debug_info_t *db_info)
{
- int i;
-
if (!db_info)
return;
- if (refcount_dec_and_test(&db_info->ref_count)) {
- for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
- if (!db_info->views[i])
- continue;
- debugfs_remove(db_info->debugfs_entries[i]);
- }
- debugfs_remove(db_info->debugfs_root_entry);
- if (db_info == debug_area_first)
- debug_area_first = db_info->next;
- if (db_info == debug_area_last)
- debug_area_last = db_info->prev;
- if (db_info->prev)
- db_info->prev->next = db_info->next;
- if (db_info->next)
- db_info->next->prev = db_info->prev;
+ if (refcount_dec_and_test(&db_info->ref_count))
debug_info_free(db_info);
- }
}

/*
@@ -635,6 +600,31 @@ static int debug_close(struct inode *inode, struct file *file)
return 0; /* success */
}

+/* Create debugfs entries and add to internal list. */
+static void _debug_register(debug_info_t *id)
+{
+ /* create root directory */
+ id->debugfs_root_entry = debugfs_create_dir(id->name,
+ debug_debugfs_root_entry);
+
+ /* append new element to linked list */
+ if (!debug_area_first) {
+ /* first element in list */
+ debug_area_first = id;
+ id->prev = NULL;
+ } else {
+ /* append element to end of list */
+ debug_area_last->next = id;
+ id->prev = debug_area_last;
+ }
+ debug_area_last = id;
+ id->next = NULL;
+
+ debug_register_view(id, &debug_level_view);
+ debug_register_view(id, &debug_flush_view);
+ debug_register_view(id, &debug_pages_view);
+}
+
/**
* debug_register_mode() - creates and initializes debug area.
*
@@ -664,19 +654,16 @@ debug_info_t *debug_register_mode(const char *name, int pages_per_area,
if ((uid != 0) || (gid != 0))
pr_warn("Root becomes the owner of all s390dbf files in sysfs\n");
BUG_ON(!initialized);
- mutex_lock(&debug_mutex);

/* create new debug_info */
rc = debug_info_create(name, pages_per_area, nr_areas, buf_size, mode);
- if (!rc)
- goto out;
- debug_register_view(rc, &debug_level_view);
- debug_register_view(rc, &debug_flush_view);
- debug_register_view(rc, &debug_pages_view);
-out:
- if (!rc)
+ if (rc) {
+ mutex_lock(&debug_mutex);
+ _debug_register(rc);
+ mutex_unlock(&debug_mutex);
+ } else {
pr_err("Registering debug feature %s failed\n", name);
- mutex_unlock(&debug_mutex);
+ }
return rc;
}
EXPORT_SYMBOL(debug_register_mode);
@@ -705,6 +692,27 @@ debug_info_t *debug_register(const char *name, int pages_per_area,
}
EXPORT_SYMBOL(debug_register);

+/* Remove debugfs entries and remove from internal list. */
+static void _debug_unregister(debug_info_t *id)
+{
+ int i;
+
+ for (i = 0; i < DEBUG_MAX_VIEWS; i++) {
+ if (!id->views[i])
+ continue;
+ debugfs_remove(id->debugfs_entries[i]);
+ }
+ debugfs_remove(id->debugfs_root_entry);
+ if (id == debug_area_first)
+ debug_area_first = id->next;
+ if (id == debug_area_last)
+ debug_area_last = id->prev;
+ if (id->prev)
+ id->prev->next = id->next;
+ if (id->next)
+ id->next->prev = id->prev;
+}
+
/**
* debug_unregister() - give back debug area.
*
@@ -718,8 +726,10 @@ void debug_unregister(debug_info_t *id)
if (!id)
return;
mutex_lock(&debug_mutex);
- debug_info_put(id);
+ _debug_unregister(id);
mutex_unlock(&debug_mutex);
+
+ debug_info_put(id);
}
EXPORT_SYMBOL(debug_unregister);

--
2.30.2