fuse: skip blocking on allocations of synchronous requests

A task may have at most one synchronous request allocated. So these
requests need not be otherwise limited.

The patch re-works fuse_get_req() to follow this idea.

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

3 files changed, 21 insertions, 13 deletions

diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index f563e78852b7..c59c097eb2e9 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -504,7 +504,6 @@ static int cuse_channel_open(struct inode *inode, struct file *file)
         cc->fc.release = cuse_fc_release;
 
         cc->fc.connected = 1;
-        cc->fc.blocked = 0;
         cc->fc.initialized = 1;
         rc = cuse_send_init(cc);
         if (rc) {
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 39c2fe3ba93d..d692b85115bd 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -130,21 +130,30 @@ static void fuse_req_init_context(struct fuse_req *req)
         req->in.h.pid = current->pid;
 }
 
+static bool fuse_block_alloc(struct fuse_conn *fc, bool for_background)
+{
+        return !fc->initialized || (for_background && fc->blocked);
+}
+
 static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
                                        bool for_background)
 {
         struct fuse_req *req;
-        sigset_t oldset;
-        int intr;
         int err;
-
         atomic_inc(&fc->num_waiting);
-        block_sigs(&oldset);
-        intr = wait_event_interruptible(fc->blocked_waitq, !fc->blocked);
-        restore_sigs(&oldset);
-        err = -EINTR;
-        if (intr)
-                goto out;
+
+        if (fuse_block_alloc(fc, for_background)) {
+                sigset_t oldset;
+                int intr;
+
+                block_sigs(&oldset);
+                intr = wait_event_interruptible(fc->blocked_waitq,
+                                !fuse_block_alloc(fc, for_background));
+                restore_sigs(&oldset);
+                err = -EINTR;
+                if (intr)
+                        goto out;
+        }
 
         err = -ENOTCONN;
         if (!fc->connected)
@@ -239,7 +248,7 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
         struct fuse_req *req;
 
         atomic_inc(&fc->num_waiting);
-        wait_event(fc->blocked_waitq, !fc->blocked);
+        wait_event(fc->blocked_waitq, fc->initialized);
         req = fuse_request_alloc(0);
         if (!req)
                 req = get_reserved_req(fc, file);
@@ -2106,6 +2115,7 @@ int fuse_dev_release(struct inode *inode, struct file *file)
                 spin_lock(&fc->lock);
                 fc->connected = 0;
                 fc->blocked = 0;
+                fc->initialized = 1;
                 end_queued_requests(fc);
                 end_polls(fc);
                 wake_up_all(&fc->blocked_waitq);
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 4958f8099f16..17ec1f70524d 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -583,7 +583,7 @@ void fuse_conn_init(struct fuse_conn *fc)
         fc->khctr = 0;
         fc->polled_files = RB_ROOT;
         fc->reqctr = 0;
-        fc->blocked = 1;
+        fc->blocked = 0;
         fc->initialized = 0;
         fc->attr_version = 1;
         get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key));
@@ -883,7 +883,6 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
                 fc->max_write = max_t(unsigned, 4096, fc->max_write);
                 fc->conn_init = 1;
         }
-        fc->blocked = 0;
         fc->initialized = 1;
         wake_up_all(&fc->blocked_waitq);
 }