fuse: convert from readpages to readahead

Implement the new readahead operation in fuse by using __readahead_batch()
to fill the array of pages in fuse_args_pages directly.  This lets us
inline fuse_readpages_fill() into fuse_readahead().

[willy@infradead.org: build fix]
Link: http://lkml.kernel.org/r/20200415025938.GB5820@bombadil.infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Gao Xiang <gaoxiang25@huawei.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: http://lkml.kernel.org/r/20200414150233.24495-25-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 9d67b83..bac51c3 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -915,84 +915,40 @@ 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(void *_data, struct page *page)
+static void fuse_readahead(struct readahead_control *rac)
 {
-       struct fuse_fill_data *data = _data;
-       struct fuse_io_args *ia = data->ia;
-       struct fuse_args_pages *ap = &ia->ap;
-       struct inode *inode = data->inode;
+       struct inode *inode = rac->mapping->host;
        struct fuse_conn *fc = get_fuse_conn(inode);
+       unsigned int i, max_pages, nr_pages = 0;
 
-       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) {
-                       unlock_page(page);
-                       return -ENOMEM;
-               }
-               ap = &ia->ap;
-       }
-
-       if (WARN_ON(ap->num_pages >= data->max_pages)) {
-               unlock_page(page);
-               fuse_io_free(ia);
-               return -EIO;
-       }
-
-       get_page(page);
-       ap->pages[ap->num_pages] = page;
-       ap->descs[ap->num_pages].length = PAGE_SIZE;
-       ap->num_pages++;
-       data->nr_pages--;
-       return 0;
-}
-
-static int fuse_readpages(struct file *file, struct address_space *mapping,
-                         struct list_head *pages, unsigned nr_pages)
-{
-       struct inode *inode = mapping->host;
-       struct fuse_conn *fc = get_fuse_conn(inode);
-       struct fuse_fill_data data;
-       int err;
-
-       err = -EIO;
        if (is_bad_inode(inode))
-               goto out;
+               return;
 
-       data.file = file;
-       data.inode = inode;
-       data.nr_pages = nr_pages;
-       data.max_pages = min_t(unsigned int, nr_pages, fc->max_pages);
-;
-       data.ia = fuse_io_alloc(NULL, data.max_pages);
-       err = -ENOMEM;
-       if (!data.ia)
-               goto out;
+       max_pages = min_t(unsigned int, fc->max_pages,
+                       fc->max_read / PAGE_SIZE);
 
-       err = read_cache_pages(mapping, pages, fuse_readpages_fill, &data);
-       if (!err) {
-               if (data.ia->ap.num_pages)
-                       fuse_send_readpages(data.ia, file);
-               else
-                       fuse_io_free(data.ia);
+       for (;;) {
+               struct fuse_io_args *ia;
+               struct fuse_args_pages *ap;
+
+               nr_pages = readahead_count(rac) - nr_pages;
+               if (nr_pages > max_pages)
+                       nr_pages = max_pages;
+               if (nr_pages == 0)
+                       break;
+               ia = fuse_io_alloc(NULL, nr_pages);
+               if (!ia)
+                       return;
+               ap = &ia->ap;
+               nr_pages = __readahead_batch(rac, ap->pages, nr_pages);
+               for (i = 0; i < nr_pages; i++) {
+                       fuse_wait_on_page_writeback(inode,
+                                                   readahead_index(rac) + i);
+                       ap->descs[i].length = PAGE_SIZE;
+               }
+               ap->num_pages = nr_pages;
+               fuse_send_readpages(ia, rac->file);
        }
-out:
-       return err;
 }
 
 static ssize_t fuse_cache_read_iter(struct kiocb *iocb, struct iov_iter *to)
@@ -3373,10 +3329,10 @@ static const struct file_operations fuse_file_operations = {
 
 static const struct address_space_operations fuse_file_aops  = {
        .readpage       = fuse_readpage,
+       .readahead      = fuse_readahead,
        .writepage      = fuse_writepage,
        .writepages     = fuse_writepages,
        .launder_page   = fuse_launder_page,
-       .readpages      = fuse_readpages,
        .set_page_dirty = __set_page_dirty_nobuffers,
        .bmap           = fuse_bmap,
        .direct_IO      = fuse_direct_IO,