Re: [PATCH v10 24/25] fuse: Convert from readpages to readahead

Matthew Wilcox
2020-03-25T12:02:58Z

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)