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authorDavid Howells <dhowells@redhat.com>2015-02-24 10:05:28 +0000
committerDavid Howells <dhowells@redhat.com>2015-04-02 14:28:53 +0100
commit418b7eb9e1011bc11220a03ad0045885d04698d2 (patch)
treed39aa74ea6c7251a396ccbd5d220a54b1cdcf140
parent87021526300f1a292dd966e141e183630ac95317 (diff)
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FS-Cache: Permit fscache_cancel_op() to cancel in-progress operations too
Currently, fscache_cancel_op() only cancels pending operations - attempts to cancel in-progress operations are ignored. This leads to a problem in fscache_wait_for_operation_activation() whereby the wait is terminated, but the object has been killed. The check at the end of the function now triggers because it's no longer contingent on the cache having produced an I/O error since the commit that fixed the logic error in fscache_object_is_dead(). The result of the check is that it tries to cancel the operation - but since the object may not be pending by this point, the cancellation request may be ignored - with the result that the the object is just put by the caller and fscache_put_operation has an assertion failure because the operation isn't in either the COMPLETE or the CANCELLED states. To fix this, we permit in-progress ops to be cancelled under some circumstances. The bug results in an oops that looks something like this: FS-Cache: fscache_wait_for_operation_activation() = -ENOBUFS [obj dead 3] FS-Cache: FS-Cache: Assertion failed FS-Cache: 3 == 5 is false ------------[ cut here ]------------ kernel BUG at ../fs/fscache/operation.c:432! ... RIP: 0010:[<ffffffffa0088574>] fscache_put_operation+0xf2/0x2cd Call Trace: [<ffffffffa008b92a>] __fscache_read_or_alloc_pages+0x2ec/0x3b3 [<ffffffffa00b761f>] __nfs_readpages_from_fscache+0x59/0xbf [nfs] [<ffffffffa00b06c5>] nfs_readpages+0x10c/0x185 [nfs] [<ffffffff81124925>] ? alloc_pages_current+0x119/0x13e [<ffffffff810ee5fd>] ? __page_cache_alloc+0xfb/0x10a [<ffffffff810f87f8>] __do_page_cache_readahead+0x188/0x22c [<ffffffff810f8b3a>] ondemand_readahead+0x29e/0x2af [<ffffffff810f8c92>] page_cache_sync_readahead+0x38/0x3a [<ffffffff810ef337>] generic_file_read_iter+0x1a2/0x55a [<ffffffffa00a9dff>] ? nfs_revalidate_mapping+0xd6/0x288 [nfs] [<ffffffffa00a6a23>] nfs_file_read+0x49/0x70 [nfs] [<ffffffff811363be>] new_sync_read+0x78/0x9c [<ffffffff81137164>] __vfs_read+0x13/0x38 [<ffffffff8113721e>] vfs_read+0x95/0x121 [<ffffffff811372f6>] SyS_read+0x4c/0x8a [<ffffffff81557a52>] system_call_fastpath+0x12/0x17 Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Steve Dickson <steved@redhat.com> Acked-by: Jeff Layton <jeff.layton@primarydata.com>
-rw-r--r--fs/fscache/internal.h3
-rw-r--r--fs/fscache/operation.c20
-rw-r--r--fs/fscache/page.c4
3 files changed, 21 insertions, 6 deletions
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 3063a58b7d3d..87c4544ec912 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -125,7 +125,8 @@ extern int fscache_submit_exclusive_op(struct fscache_object *,
extern int fscache_submit_op(struct fscache_object *,
struct fscache_operation *);
extern int fscache_cancel_op(struct fscache_operation *,
- void (*)(struct fscache_operation *));
+ void (*)(struct fscache_operation *),
+ bool);
extern void fscache_cancel_all_ops(struct fscache_object *);
extern void fscache_abort_object(struct fscache_object *);
extern void fscache_start_operations(struct fscache_object *);
diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c
index 18658fffbba1..67594a8d791a 100644
--- a/fs/fscache/operation.c
+++ b/fs/fscache/operation.c
@@ -312,9 +312,11 @@ void fscache_start_operations(struct fscache_object *object)
* cancel an operation that's pending on an object
*/
int fscache_cancel_op(struct fscache_operation *op,
- void (*do_cancel)(struct fscache_operation *))
+ void (*do_cancel)(struct fscache_operation *),
+ bool cancel_in_progress_op)
{
struct fscache_object *object = op->object;
+ bool put = false;
int ret;
_enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
@@ -328,8 +330,19 @@ int fscache_cancel_op(struct fscache_operation *op,
ret = -EBUSY;
if (op->state == FSCACHE_OP_ST_PENDING) {
ASSERT(!list_empty(&op->pend_link));
- fscache_stat(&fscache_n_op_cancelled);
list_del_init(&op->pend_link);
+ put = true;
+ fscache_stat(&fscache_n_op_cancelled);
+ if (do_cancel)
+ do_cancel(op);
+ op->state = FSCACHE_OP_ST_CANCELLED;
+ if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
+ object->n_exclusive--;
+ if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
+ wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
+ ret = 0;
+ } else if (op->state == FSCACHE_OP_ST_IN_PROGRESS && cancel_in_progress_op) {
+ fscache_stat(&fscache_n_op_cancelled);
if (do_cancel)
do_cancel(op);
op->state = FSCACHE_OP_ST_CANCELLED;
@@ -337,10 +350,11 @@ int fscache_cancel_op(struct fscache_operation *op,
object->n_exclusive--;
if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
- fscache_put_operation(op);
ret = 0;
}
+ if (put)
+ fscache_put_operation(op);
spin_unlock(&object->lock);
_leave(" = %d", ret);
return ret;
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index d0805e31361c..433cae927eca 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -359,7 +359,7 @@ int fscache_wait_for_operation_activation(struct fscache_object *object,
fscache_stat(stat_op_waits);
if (wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
TASK_INTERRUPTIBLE) != 0) {
- ret = fscache_cancel_op(op, do_cancel);
+ ret = fscache_cancel_op(op, do_cancel, false);
if (ret == 0)
return -ERESTARTSYS;
@@ -380,7 +380,7 @@ check_if_dead:
if (unlikely(fscache_object_is_dying(object) ||
fscache_cache_is_broken(object))) {
enum fscache_operation_state state = op->state;
- fscache_cancel_op(op, do_cancel);
+ fscache_cancel_op(op, do_cancel, true);
if (stat_object_dead)
fscache_stat(stat_object_dead);
_leave(" = -ENOBUFS [obj dead %d]", state);