fuse: rework fuse_readpages()

The patch uses 'nr_pages' argument of fuse_readpages() as heuristics for the
number of page pointers to allocate.

This can be improved further by taking in consideration fc->max_read and gaps
between page indices, but it's not clear whether it's worthy or not.

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

1 files changed, 14 insertions, 2 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 882877125c1d..5fd06bae1790 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -641,6 +641,7 @@ struct fuse_fill_data {
         struct fuse_req *req;
         struct file *file;
         struct inode *inode;
+        unsigned nr_pages;
 };
 
 static int fuse_readpages_fill(void *_data, struct page *page)
@@ -656,16 +657,25 @@ static int fuse_readpages_fill(void *_data, struct page *page)
             (req->num_pages == FUSE_MAX_PAGES_PER_REQ ||
              (req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_read ||
              req->pages[req->num_pages - 1]->index + 1 != page->index)) {
+                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, FUSE_MAX_PAGES_PER_REQ);
+                data->req = req = fuse_get_req(fc, nr_alloc);
                 if (IS_ERR(req)) {
                         unlock_page(page);
                         return PTR_ERR(req);
                 }
         }
+
+        if (WARN_ON(req->num_pages >= req->max_pages)) {
+                fuse_put_request(fc, req);
+                return -EIO;
+        }
+
         page_cache_get(page);
         req->pages[req->num_pages] = page;
         req->num_pages++;
+        data->nr_pages--;
         return 0;
 }
 
@@ -676,6 +686,7 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
         struct fuse_conn *fc = get_fuse_conn(inode);
         struct fuse_fill_data data;
         int err;
+        int nr_alloc = min_t(unsigned, nr_pages, FUSE_MAX_PAGES_PER_REQ);
 
         err = -EIO;
         if (is_bad_inode(inode))
@@ -683,7 +694,8 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
 
         data.file = file;
         data.inode = inode;
-        data.req = fuse_get_req(fc, FUSE_MAX_PAGES_PER_REQ);
+        data.req = fuse_get_req(fc, nr_alloc);
+        data.nr_pages = nr_pages;
         err = PTR_ERR(data.req);
         if (IS_ERR(data.req))
                 goto out;