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>

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 8828771..5fd06ba 100644 (file)
--- 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;