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authorDavid Howells <dhowells@redhat.com>2015-02-24 10:05:27 +0000
committerDavid Howells <dhowells@redhat.com>2015-04-02 14:28:53 +0100
commit30ceec6284129662efc3a1e7675b2bd857a046fe (patch)
tree98fba830445abbf24eb3fc969564fc20e29c04a8 /fs/fscache
parent3c3059841a9b99fa8dd8d878607deceec1e363e9 (diff)
FS-Cache: When submitting an op, cancel it if the target object is dying
When submitting an operation, prefer to cancel the operation immediately rather than queuing it for later processing if the object is marked as dying (ie. the object state machine has reached the KILL_OBJECT state). Whilst we're at it, change the series of related test_bit() calls into a READ_ONCE() and bitwise-AND operators to reduce the number of load instructions (test_bit() has a volatile address). Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Steve Dickson <steved@redhat.com> Acked-by: Jeff Layton <jeff.layton@primarydata.com>
Diffstat (limited to 'fs/fscache')
-rw-r--r--fs/fscache/operation.c47
1 files changed, 30 insertions, 17 deletions
diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c
index 68ead8482617..dec6defe3be3 100644
--- a/fs/fscache/operation.c
+++ b/fs/fscache/operation.c
@@ -120,6 +120,8 @@ static void fscache_report_unexpected_submission(struct fscache_object *object,
int fscache_submit_exclusive_op(struct fscache_object *object,
struct fscache_operation *op)
{
+ const struct fscache_state *ostate;
+ unsigned long flags;
int ret;
_enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
@@ -132,8 +134,19 @@ int fscache_submit_exclusive_op(struct fscache_object *object,
ASSERTCMP(object->n_ops, >=, object->n_exclusive);
ASSERT(list_empty(&op->pend_link));
+ ostate = object->state;
+ smp_rmb();
+
op->state = FSCACHE_OP_ST_PENDING;
- if (fscache_object_is_active(object)) {
+ flags = READ_ONCE(object->flags);
+ if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
+ fscache_stat(&fscache_n_op_rejected);
+ op->state = FSCACHE_OP_ST_CANCELLED;
+ ret = -ENOBUFS;
+ } else if (unlikely(fscache_cache_is_broken(object))) {
+ op->state = FSCACHE_OP_ST_CANCELLED;
+ ret = -EIO;
+ } else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
op->object = object;
object->n_ops++;
object->n_exclusive++; /* reads and writes must wait */
@@ -155,7 +168,7 @@ int fscache_submit_exclusive_op(struct fscache_object *object,
/* need to issue a new write op after this */
clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
ret = 0;
- } else if (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
+ } else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
op->object = object;
object->n_ops++;
object->n_exclusive++; /* reads and writes must wait */
@@ -164,11 +177,9 @@ int fscache_submit_exclusive_op(struct fscache_object *object,
fscache_stat(&fscache_n_op_pend);
ret = 0;
} else {
- /* 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;
+ fscache_report_unexpected_submission(object, op, ostate);
+ op->state = FSCACHE_OP_ST_CANCELLED;
+ ret = -ENOBUFS;
}
spin_unlock(&object->lock);
@@ -187,6 +198,7 @@ int fscache_submit_op(struct fscache_object *object,
struct fscache_operation *op)
{
const struct fscache_state *ostate;
+ unsigned long flags;
int ret;
_enter("{OBJ%x OP%x},{%u}",
@@ -204,7 +216,15 @@ int fscache_submit_op(struct fscache_object *object,
smp_rmb();
op->state = FSCACHE_OP_ST_PENDING;
- if (fscache_object_is_active(object)) {
+ flags = READ_ONCE(object->flags);
+ if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
+ fscache_stat(&fscache_n_op_rejected);
+ op->state = FSCACHE_OP_ST_CANCELLED;
+ ret = -ENOBUFS;
+ } else if (unlikely(fscache_cache_is_broken(object))) {
+ op->state = FSCACHE_OP_ST_CANCELLED;
+ ret = -EIO;
+ } else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
op->object = object;
object->n_ops++;
@@ -222,25 +242,18 @@ int fscache_submit_op(struct fscache_object *object,
fscache_run_op(object, op);
}
ret = 0;
- } else if (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
+ } else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
op->object = object;
object->n_ops++;
atomic_inc(&op->usage);
list_add_tail(&op->pend_link, &object->pending_ops);
fscache_stat(&fscache_n_op_pend);
ret = 0;
- } else if (fscache_object_is_dying(object)) {
- fscache_stat(&fscache_n_op_rejected);
- op->state = FSCACHE_OP_ST_CANCELLED;
- ret = -ENOBUFS;
- } else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
+ } else {
fscache_report_unexpected_submission(object, op, ostate);
ASSERT(!fscache_object_is_active(object));
op->state = FSCACHE_OP_ST_CANCELLED;
ret = -ENOBUFS;
- } else {
- op->state = FSCACHE_OP_ST_CANCELLED;
- ret = -ENOBUFS;
}
spin_unlock(&object->lock);