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authorMaxim Patlasov <mpatlasov@parallels.com>2013-03-21 18:02:36 +0400
committerMiklos Szeredi <mszeredi@suse.cz>2013-04-17 12:31:45 +0200
commit722d2bea8c601d0744e4a37170533fdf6214a678 (patch)
tree3762894f78f98474c73e1a8120da2dd1598c3673 /fs/fuse
parent0aada88476a33690c9569b094191ce92a38e6541 (diff)
fuse: implement exclusive wakeup for blocked_waitq
The patch solves thundering herd problem. So far as previous patches ensured that only allocations for background may block, it's safe to wake up one waiter. Whoever it is, it will wake up another one in request_end() afterwards. Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Diffstat (limited to 'fs/fuse')
-rw-r--r--fs/fuse/dev.c29
1 files changed, 24 insertions, 5 deletions
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index d692b85115bd..367310588962 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -147,7 +147,7 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
int intr;
block_sigs(&oldset);
- intr = wait_event_interruptible(fc->blocked_waitq,
+ intr = wait_event_interruptible_exclusive(fc->blocked_waitq,
!fuse_block_alloc(fc, for_background));
restore_sigs(&oldset);
err = -EINTR;
@@ -161,8 +161,11 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
req = fuse_request_alloc(npages);
err = -ENOMEM;
- if (!req)
+ if (!req) {
+ if (for_background)
+ wake_up(&fc->blocked_waitq);
goto out;
+ }
fuse_req_init_context(req);
req->waiting = 1;
@@ -262,6 +265,17 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
{
if (atomic_dec_and_test(&req->count)) {
+ if (unlikely(req->background)) {
+ /*
+ * We get here in the unlikely case that a background
+ * request was allocated but not sent
+ */
+ spin_lock(&fc->lock);
+ if (!fc->blocked)
+ wake_up(&fc->blocked_waitq);
+ spin_unlock(&fc->lock);
+ }
+
if (req->waiting)
atomic_dec(&fc->num_waiting);
@@ -359,10 +373,15 @@ __releases(fc->lock)
list_del(&req->intr_entry);
req->state = FUSE_REQ_FINISHED;
if (req->background) {
- if (fc->num_background == fc->max_background) {
+ req->background = 0;
+
+ if (fc->num_background == fc->max_background)
fc->blocked = 0;
- wake_up_all(&fc->blocked_waitq);
- }
+
+ /* Wake up next waiter, if any */
+ if (!fc->blocked)
+ wake_up(&fc->blocked_waitq);
+
if (fc->num_background == fc->congestion_threshold &&
fc->connected && fc->bdi_initialized) {
clear_bdi_congested(&fc->bdi, BLK_RW_SYNC);