The .writepages one is required to make each writeback request carry more than
one page on it.
Changed in v2:
- fixed fuse_prepare_write() to avoid reads beyond EOF
- fixed fuse_prepare_write() to zero uninitialized part of page
Original patch by: Pavel Emelyanov <xemul@xxxxxxxxxx>
Signed-off-by: Maxim V. Patlasov <MPatlasov@xxxxxxxxxxxxx>
---
fs/fuse/file.c | 282 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 281 insertions(+), 1 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 496e74c..3b4dc98 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -722,7 +722,10 @@ static void fuse_send_readpages(struct fuse_req *req, struct file *file)
struct fuse_fill_data {
struct fuse_req *req;
- struct file *file;
+ union {
+ struct file *file;
+ struct fuse_file *ff;
+ };
struct inode *inode;
unsigned nr_pages;
};
@@ -1530,6 +1533,280 @@ static int fuse_writepage(struct page *page, struct writeback_control *wbc)
return err;
}
+static int fuse_send_writepages(struct fuse_fill_data *data)
+{
+ int i, all_ok = 1;
+ struct fuse_req *req = data->req;
+ struct inode *inode = data->inode;
+ struct backing_dev_info *bdi = inode->i_mapping->backing_dev_info;
+ struct fuse_conn *fc = get_fuse_conn(inode);
+ struct fuse_inode *fi = get_fuse_inode(inode);
+ loff_t off = -1;
+
+ if (!data->ff)
+ data->ff = fuse_write_file(fc, fi);
+
+ if (!data->ff) {
+ for (i = 0; i < req->num_pages; i++)
+ end_page_writeback(req->pages[i]);
+ return -EIO;
+ }
+
+ req->inode = inode;
+ req->misc.write.in.offset = page_offset(req->pages[0]);
+
+ spin_lock(&fc->lock);
+ list_add(&req->writepages_entry, &fi->writepages);
+ spin_unlock(&fc->lock);
+
+ for (i = 0; i < req->num_pages; i++) {
+ struct page *page = req->pages[i];
+ struct page *tmp_page;
+
+ tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+ if (tmp_page) {
+ copy_highpage(tmp_page, page);
+ inc_bdi_stat(bdi, BDI_WRITEBACK);
+ inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP);
+ } else
+ all_ok = 0;
+ req->pages[i] = tmp_page;
+ if (i == 0)
+ off = page_offset(page);
+
+ end_page_writeback(page);
+ }
+
+ if (!all_ok) {
+ for (i = 0; i < req->num_pages; i++) {
+ struct page *page = req->pages[i];
+ if (page) {
+ dec_bdi_stat(bdi, BDI_WRITEBACK);
+ dec_zone_page_state(page, NR_WRITEBACK_TEMP);
+ __free_page(page);
+ req->pages[i] = NULL;
+ }
+ }
+
+ spin_lock(&fc->lock);
+ list_del(&req->writepages_entry);
+ wake_up(&fi->page_waitq);
+ spin_unlock(&fc->lock);
+ return -ENOMEM;
+ }
+
+ req->ff = fuse_file_get(data->ff);
+ fuse_write_fill(req, data->ff, off, 0);
+
+ req->misc.write.in.write_flags |= FUSE_WRITE_CACHE;
+ req->in.argpages = 1;
+ fuse_page_descs_length_init(req, 0, req->num_pages);
+ req->end = fuse_writepage_end;
+
+ spin_lock(&fc->lock);
+ list_add_tail(&req->list, &fi->queued_writes);
+ fuse_flush_writepages(data->inode);
+ spin_unlock(&fc->lock);
+
+ return 0;
+}
+
+static int fuse_writepages_fill(struct page *page,
+ struct writeback_control *wbc, void *_data)
+{
+ struct fuse_fill_data *data = _data;
+ struct fuse_req *req = data->req;
+ struct inode *inode = data->inode;
+ struct fuse_conn *fc = get_fuse_conn(inode);
+
+ if (fuse_page_is_writeback(inode, page->index)) {
+ if (wbc->sync_mode != WB_SYNC_ALL) {
+ redirty_page_for_writepage(wbc, page);
+ unlock_page(page);
+ return 0;
+ }
+ fuse_wait_on_page_writeback(inode, page->index);
+ }
+
+ if (req->num_pages &&
+ (req->num_pages == FUSE_MAX_PAGES_PER_REQ ||
+ (req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_write ||
+ req->pages[req->num_pages - 1]->index + 1 != page->index)) {
+ int err;
+
+ err = fuse_send_writepages(data);
+ if (err) {
+ unlock_page(page);
+ return err;
+ }
+
+ data->req = req =
+ fuse_request_alloc_nofs(FUSE_MAX_PAGES_PER_REQ);
+ if (!req) {
+ unlock_page(page);
+ return -ENOMEM;
+ }
+ }
+
+ req->pages[req->num_pages] = page;
+ req->num_pages++;
+
+ if (test_set_page_writeback(page))
+ BUG();
+
+ unlock_page(page);
+
+ return 0;
+}
+
+static int fuse_writepages(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ struct inode *inode = mapping->host;
+ struct fuse_conn *fc = get_fuse_conn(inode);
+ struct fuse_fill_data data;
+ int err;
+
+ if (!fc->writeback_cache)
+ return generic_writepages(mapping, wbc);
+
+ err = -EIO;
+ if (is_bad_inode(inode))
+ goto out;
+
+ data.ff = NULL;
+ data.inode = inode;
+ data.req = fuse_request_alloc_nofs(FUSE_MAX_PAGES_PER_REQ);
+ err = -ENOMEM;
+ if (!data.req)
+ goto out_put;
+
+ err = write_cache_pages(mapping, wbc, fuse_writepages_fill, &data);
+ if (data.req) {
+ if (!err && data.req->num_pages) {
+ err = fuse_send_writepages(&data);
+ if (err)
+ fuse_put_request(fc, data.req);
+ } else
+ fuse_put_request(fc, data.req);
+ }
+out_put:
+ if (data.ff)
+ fuse_file_put(data.ff, false);
+out:
+ return err;
+}
+
+/*
+ * Determine the number of bytes of data the page contains
+ */
+static inline unsigned fuse_page_length(struct page *page)
+{
+ loff_t i_size = i_size_read(page_file_mapping(page)->host);
+
+ if (i_size > 0) {
+ pgoff_t page_index = page_file_index(page);
+ pgoff_t end_index = (i_size - 1) >> PAGE_CACHE_SHIFT;
+ if (page_index < end_index)
+ return PAGE_CACHE_SIZE;
+ if (page_index == end_index)
+ return ((i_size - 1) & ~PAGE_CACHE_MASK) + 1;
+ }
+ return 0;
+}
+
+static int fuse_prepare_write(struct fuse_conn *fc, struct file *file,
+ struct page *page, loff_t pos, unsigned len)
+{
+ struct fuse_req *req;
+ unsigned num_read;
+ unsigned page_len;
+ int err;
+
+ if (PageUptodate(page) || (len == PAGE_CACHE_SIZE))
+ return 0;
+
+ page_len = fuse_page_length(page);
+ if (!page_len) {
+ zero_user(page, 0, PAGE_CACHE_SIZE);
+ return 0;
+ }
+
+ /*
+ * Page writeback can extend beyond the lifetime of the
+ * page-cache page, so make sure we read a properly synced
+ * page.
+ */
+ fuse_wait_on_page_writeback(page->mapping->host, page->index);
+
+ req = fuse_get_req(fc, 1);
+ err = PTR_ERR(req);
+ if (IS_ERR(req))
+ goto out;
+
+ req->out.page_zeroing = 1;
+ req->out.argpages = 1;
+ req->num_pages = 1;
+ req->pages[0] = page;
+ req->page_descs[0].offset = 0;
+ req->page_descs[0].length = PAGE_SIZE;
+ num_read = fuse_send_read(req, file, page_offset(page), page_len, NULL);
+ err = req->out.h.error;
+ fuse_put_request(fc, req);
+out:
+ if (err) {
+ unlock_page(page);
+ page_cache_release(page);
+ } else if (num_read != PAGE_CACHE_SIZE) {
+ zero_user_segment(page, num_read, PAGE_CACHE_SIZE);
+ }
+ return err;
+}
