fuse: make request allocations for background processing explicit

There are two types of processing requests in FUSE: synchronous (via
fuse_request_send()) and asynchronous (via adding to fc->bg_queue).

Fortunately, the type of processing is always known in advance, at the time
of request allocation. This preparatory patch utilizes this fact making
fuse_get_req() aware about the type. Next patches will use it.

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

5 files changed, 37 insertions, 5 deletions

diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index 6f96a8def147..b7c7f3060635 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -422,7 +422,7 @@ static int cuse_send_init(struct cuse_conn *cc)
 
         BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);
 
-        req = fuse_get_req(fc, 1);
+        req = fuse_get_req_for_background(fc, 1);
         if (IS_ERR(req)) {
                 rc = PTR_ERR(req);
                 goto err;
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 11dfa0c3fb46..3b8301f5c0e1 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -130,7 +130,8 @@ static void fuse_req_init_context(struct fuse_req *req)
         req->in.h.pid = current->pid;
 }
 
-struct fuse_req *fuse_get_req(struct fuse_conn *fc, unsigned npages)
+static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
+                                       bool for_background)
 {
         struct fuse_req *req;
         sigset_t oldset;
@@ -156,14 +157,27 @@ struct fuse_req *fuse_get_req(struct fuse_conn *fc, unsigned npages)
 
         fuse_req_init_context(req);
         req->waiting = 1;
+        req->background = for_background;
         return req;
 
  out:
         atomic_dec(&fc->num_waiting);
         return ERR_PTR(err);
 }
+
+struct fuse_req *fuse_get_req(struct fuse_conn *fc, unsigned npages)
+{
+        return __fuse_get_req(fc, npages, false);
+}
 EXPORT_SYMBOL_GPL(fuse_get_req);
 
+struct fuse_req *fuse_get_req_for_background(struct fuse_conn *fc,
+                                             unsigned npages)
+{
+        return __fuse_get_req(fc, npages, true);
+}
+EXPORT_SYMBOL_GPL(fuse_get_req_for_background);
+
 /*
  * Return request in fuse_file->reserved_req.  However that may
  * currently be in use.  If that is the case, wait for it to become
@@ -232,6 +246,7 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
 
         fuse_req_init_context(req);
         req->waiting = 1;
+        req->background = 0;
         return req;
 }
 
@@ -442,6 +457,7 @@ __acquires(fc->lock)
 
 static void __fuse_request_send(struct fuse_conn *fc, struct fuse_req *req)
 {
+        BUG_ON(req->background);
         spin_lock(&fc->lock);
         if (!fc->connected)
                 req->out.h.error = -ENOTCONN;
@@ -469,7 +485,7 @@ EXPORT_SYMBOL_GPL(fuse_request_send);
 static void fuse_request_send_nowait_locked(struct fuse_conn *fc,
                                             struct fuse_req *req)
 {
-        req->background = 1;
+        BUG_ON(!req->background);
         fc->num_background++;
         if (fc->num_background == fc->max_background)
                 fc->blocked = 1;
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 34b80ba95bad..4884790b9639 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -126,11 +126,13 @@ static void fuse_file_put(struct fuse_file *ff, bool sync)
                 struct fuse_req *req = ff->reserved_req;
 
                 if (sync) {
+                        req->background = 0;
                         fuse_request_send(ff->fc, req);
                         path_put(&req->misc.release.path);
                         fuse_put_request(ff->fc, req);
                 } else {
                         req->end = fuse_release_end;
+                        req->background = 1;
                         fuse_request_send_background(ff->fc, req);
                 }
                 kfree(ff);
@@ -282,6 +284,7 @@ void fuse_sync_release(struct fuse_file *ff, int flags)
         WARN_ON(atomic_read(&ff->count) > 1);
         fuse_prepare_release(ff, flags, FUSE_RELEASE);
         ff->reserved_req->force = 1;
+        ff->reserved_req->background = 0;
         fuse_request_send(ff->fc, ff->reserved_req);
         fuse_put_request(ff->fc, ff->reserved_req);
         kfree(ff);
@@ -661,7 +664,12 @@ static int fuse_readpages_fill(void *_data, struct page *page)
                 int nr_alloc = min_t(unsigned, data->nr_pages,
                                      FUSE_MAX_PAGES_PER_REQ);
                 fuse_send_readpages(req, data->file);
-                data->req = req = fuse_get_req(fc, nr_alloc);
+                if (fc->async_read)
+                        req = fuse_get_req_for_background(fc, nr_alloc);
+                else
+                        req = fuse_get_req(fc, nr_alloc);
+
+                data->req = req;
                 if (IS_ERR(req)) {
                         unlock_page(page);
                         return PTR_ERR(req);
@@ -696,7 +704,10 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
 
         data.file = file;
         data.inode = inode;
-        data.req = fuse_get_req(fc, nr_alloc);
+        if (fc->async_read)
+                data.req = fuse_get_req_for_background(fc, nr_alloc);
+        else
+                data.req = fuse_get_req(fc, nr_alloc);
         data.nr_pages = nr_pages;
         err = PTR_ERR(data.req);
         if (IS_ERR(data.req))
@@ -1375,6 +1386,7 @@ static int fuse_writepage_locked(struct page *page)
         if (!req)
                 goto err;
 
+        req->background = 1; /* writeback always goes to bg_queue */
         tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
         if (!tmp_page)
                 goto err_free;
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 6aeba864f070..47c94d28ff88 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -708,6 +708,8 @@ void fuse_request_free(struct fuse_req *req);
  * caller should specify # elements in req->pages[] explicitly
  */
 struct fuse_req *fuse_get_req(struct fuse_conn *fc, unsigned npages);
+struct fuse_req *fuse_get_req_for_background(struct fuse_conn *fc,
+                                             unsigned npages);
 
 /**
  * Get a request, may fail with -ENOMEM,
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 137185c3884f..e26607df93df 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -346,6 +346,7 @@ static void fuse_send_destroy(struct fuse_conn *fc)
                 fc->destroy_req = NULL;
                 req->in.h.opcode = FUSE_DESTROY;
                 req->force = 1;
+                req->background = 0;
                 fuse_request_send(fc, req);
                 fuse_put_request(fc, req);
         }
@@ -1043,6 +1044,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
         init_req = fuse_request_alloc(0);
         if (!init_req)
                 goto err_put_root;
+        init_req->background = 1;
 
         if (is_bdev) {
                 fc->destroy_req = fuse_request_alloc(0);