pstore: Solve lockdep warning by moving inode locks
Lockdep complains about a possible deadlock between mount and unlink
(which is technically impossible), but fixing this improves possible
future multiple-backend support, and keeps locking in the right order.
The lockdep warning could be triggered by unlinking a file in the
pstore filesystem:
-> #1 (&sb->s_type->i_mutex_key#14){++++++}:
lock_acquire+0xc9/0x220
down_write+0x3f/0x70
pstore_mkfile+0x1f4/0x460
pstore_get_records+0x17a/0x320
pstore_fill_super+0xa4/0xc0
mount_single+0x89/0xb0
pstore_mount+0x13/0x20
mount_fs+0xf/0x90
vfs_kern_mount+0x66/0x170
do_mount+0x190/0xd50
SyS_mount+0x90/0xd0
entry_SYSCALL_64_fastpath+0x1c/0xb1
-> #0 (&psinfo->read_mutex){+.+.+.}:
__lock_acquire+0x1ac0/0x1bb0
lock_acquire+0xc9/0x220
__mutex_lock+0x6e/0x990
mutex_lock_nested+0x16/0x20
pstore_unlink+0x3f/0xa0
vfs_unlink+0xb5/0x190
do_unlinkat+0x24c/0x2a0
SyS_unlinkat+0x16/0x30
entry_SYSCALL_64_fastpath+0x1c/0xb1
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&sb->s_type->i_mutex_key#14);
lock(&psinfo->read_mutex);
lock(&sb->s_type->i_mutex_key#14);
lock(&psinfo->read_mutex);
Reported-by: Marta Lofstedt <marta.lofstedt@intel.com>
Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 43b3ca5..d468eec 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -810,17 +810,17 @@ static void decompress_record(struct pstore_record *record)
}
/*
- * Read all the records from the persistent store. Create
+ * Read all the records from one persistent store backend. Create
* files in our filesystem. Don't warn about -EEXIST errors
* when we are re-scanning the backing store looking to add new
* error records.
*/
-void pstore_get_records(int quiet)
+void pstore_get_backend_records(struct pstore_info *psi,
+ struct dentry *root, int quiet)
{
- struct pstore_info *psi = psinfo;
int failed = 0;
- if (!psi)
+ if (!psi || !root)
return;
mutex_lock(&psi->read_mutex);
@@ -850,7 +850,7 @@ void pstore_get_records(int quiet)
break;
decompress_record(record);
- rc = pstore_mkfile(record);
+ rc = pstore_mkfile(root, record);
if (rc) {
/* pstore_mkfile() did not take record, so free it. */
kfree(record->buf);
