On Wed, Mar 25, 2020 at 10:42:56AM +0100, Miklos Szeredi wrote:
> > +       while ((page = readahead_page(rac))) {
> > +               if (fuse_readpages_fill(&data, page) != 0)
> 
> Shouldn't this unlock + put page on error?

We're certainly inconsistent between the two error exits from
fuse_readpages_fill().  But I think we can simplify the whole thing
... how does this look to you?

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 5749505bcff6..57ea9a364e62 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -915,76 +915,32 @@ static void fuse_send_readpages(struct fuse_io_args *ia, 
struct file *file)
        fuse_readpages_end(fc, &ap->args, err);
 }
 
-struct fuse_fill_data {
-       struct fuse_io_args *ia;
-       struct file *file;
-       struct inode *inode;
-       unsigned int nr_pages;
-       unsigned int max_pages;
-};
-
-static int fuse_readpages_fill(struct fuse_fill_data *data, struct page *page)
-{
-       struct fuse_io_args *ia = data->ia;
-       struct fuse_args_pages *ap = &ia->ap;
-       struct inode *inode = data->inode;
-       struct fuse_conn *fc = get_fuse_conn(inode);
-
-       fuse_wait_on_page_writeback(inode, page->index);
-
-       if (ap->num_pages &&
-           (ap->num_pages == fc->max_pages ||
-            (ap->num_pages + 1) * PAGE_SIZE > fc->max_read ||
-            ap->pages[ap->num_pages - 1]->index + 1 != page->index)) {
-               data->max_pages = min_t(unsigned int, data->nr_pages,
-                                       fc->max_pages);
-               fuse_send_readpages(ia, data->file);
-               data->ia = ia = fuse_io_alloc(NULL, data->max_pages);
-               if (!ia)
-                       return -ENOMEM;
-               ap = &ia->ap;
-       }
-
-       if (WARN_ON(ap->num_pages >= data->max_pages)) {
-               unlock_page(page);
-               fuse_io_free(ia);
-               return -EIO;
-       }
-
-       ap->pages[ap->num_pages] = page;
-       ap->descs[ap->num_pages].length = PAGE_SIZE;
-       ap->num_pages++;
-       data->nr_pages--;
-       return 0;
-}
-
 static void fuse_readahead(struct readahead_control *rac)
 {
        struct inode *inode = rac->mapping->host;
        struct fuse_conn *fc = get_fuse_conn(inode);
-       struct fuse_fill_data data;
-       struct page *page;
 
        if (is_bad_inode(inode))
                return;
 
-       data.file = rac->file;
-       data.inode = inode;
-       data.nr_pages = readahead_count(rac);
-       data.max_pages = min_t(unsigned int, data.nr_pages, fc->max_pages);
-       data.ia = fuse_io_alloc(NULL, data.max_pages);
-       if (!data.ia)
-               return;
+       while (readahead_count(rac)) {
+               struct fuse_io_args *ia;
+               struct fuse_args_pages *ap;
+               unsigned int i, nr_pages;
 
-       while ((page = readahead_page(rac))) {
-               if (fuse_readpages_fill(&data, page) != 0)
+               nr_pages = min(readahead_count(rac), fc->max_pages);
+               ia = fuse_io_alloc(NULL, nr_pages);
+               if (!ia)
                        return;
+               ap = &ia->ap;
+               __readahead_batch(rac, ap->pages, nr_pages);
+               for (i = 0; i < nr_pages; i++) {
+                       fuse_wait_on_page_writeback(inode, ap->pages[i]->index);
+                       ap->descs[i].length = PAGE_SIZE;
+               }
+               ap->num_pages = nr_pages;
+               fuse_send_readpages(ia, rac->file);
        }
-
-       if (data.ia->ap.num_pages)
-               fuse_send_readpages(data.ia, rac->file);
-       else
-               fuse_io_free(data.ia);
 }
 
 static ssize_t fuse_cache_read_iter(struct kiocb *iocb, struct iov_iter *to)


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