FS-Cache: Exclusive op submission can BUG if there's been an I/O error
The function to submit an exclusive op (fscache_submit_exclusive_op()) can BUG
if there's been an I/O error because it may see the parent cache object in an
unexpected state. It should only BUG if there hasn't been an I/O error.
In this case the problem was produced by remounting the cache partition to be
R/O. The EROFS state was detected and the cache was aborted, but not
everything handled the aborting correctly.
SysRq : Emergency Remount R/O
EXT4-fs (sda6): re-mounted. Opts: (null)
Emergency Remount complete
CacheFiles: I/O Error: Failed to update xattr with error -30
FS-Cache: Cache cachefiles stopped due to I/O error
------------[ cut here ]------------
kernel BUG at fs/fscache/operation.c:128!
invalid opcode: 0000 [#1] SMP
CPU 0
Modules linked in: cachefiles nfs fscache auth_rpcgss nfs_acl lockd sunrpc
Pid: 6612, comm: kworker/u:2 Not tainted 3.1.0-rc8-fsdevel+ #1093 /DG965RY
RIP: 0010:[<ffffffffa00739c0>] [<ffffffffa00739c0>] fscache_submit_exclusive_op+0x2ad/0x2c2 [fscache]
RSP: 0018:ffff880000853d40 EFLAGS: 00010206
RAX: ffff880038ac72a8 RBX: ffff8800181f2260 RCX: ffffffff81f2b2b0
RDX: 0000000000000001 RSI: ffffffff8179a478 RDI: ffff8800181f2280
RBP: ffff880000853d60 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffff880038ac7268
R13: ffff8800181f2280 R14: ffff88003a359190 R15: 000000010122b162
FS: 0000000000000000(0000) GS:ffff88003bc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00000034cc4a77f0 CR3: 0000000010e96000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process kworker/u:2 (pid: 6612, threadinfo ffff880000852000, task ffff880014c3c040)
Stack:
ffff8800181f2260 ffff8800181f2310 ffff880038ac7268 ffff8800181f2260
ffff880000853dc0 ffffffffa0072375 ffff880037ecfe00 ffff88003a359198
ffff880000853dc0 0000000000000246 0000000000000000 ffff88000a91d308
Call Trace:
[<ffffffffa0072375>] fscache_object_work_func+0x792/0xe65 [fscache]
[<ffffffff81047e44>] process_one_work+0x1eb/0x37f
[<ffffffff81047de6>] ? process_one_work+0x18d/0x37f
[<ffffffffa0071be3>] ? fscache_enqueue_dependents+0xd8/0xd8 [fscache]
[<ffffffff810482e4>] worker_thread+0x15a/0x21a
[<ffffffff8104818a>] ? rescuer_thread+0x188/0x188
[<ffffffff8104bf96>] kthread+0x7f/0x87
[<ffffffff813ad6f4>] kernel_thread_helper+0x4/0x10
[<ffffffff81026b98>] ? finish_task_switch+0x45/0xc0
[<ffffffff813abd1d>] ? retint_restore_args+0xe/0xe
[<ffffffff8104bf17>] ? __init_kthread_worker+0x53/0x53
[<ffffffff813ad6f0>] ? gs_change+0xb/0xb
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c
index c58dbe6..9e6b7d2 100644
--- a/fs/fscache/operation.c
+++ b/fs/fscache/operation.c
@@ -84,6 +84,8 @@
int fscache_submit_exclusive_op(struct fscache_object *object,
struct fscache_operation *op)
{
+ int ret;
+
_enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
@@ -116,6 +118,7 @@
/* need to issue a new write op after this */
clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
+ ret = 0;
} else if (object->state == FSCACHE_OBJECT_CREATING) {
op->object = object;
object->n_ops++;
@@ -123,13 +126,17 @@
atomic_inc(&op->usage);
list_add_tail(&op->pend_link, &object->pending_ops);
fscache_stat(&fscache_n_op_pend);
+ ret = 0;
} else {
- /* not allowed to submit ops in any other state */
- BUG();
+ /* If we're in any other state, there must have been an I/O
+ * error of some nature.
+ */
+ ASSERT(test_bit(FSCACHE_IOERROR, &object->cache->flags));
+ ret = -EIO;
}
spin_unlock(&object->lock);
- return 0;
+ return ret;
}
/*