fuse: Implement write_begin/write_end callbacks

The .write_begin and .write_end are requiered to use generic routines
(generic_file_aio_write --> ... --> generic_perform_write) for buffered
writes.

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 b1873b510350bd88343c370938619de861a9c8de..d8575304c062357f8b18fb6af8b705c2cb86bd6c 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1952,6 +1952,77 @@ out:
        return err;
 }
 
+/*
+ * It's worthy to make sure that space is reserved on disk for the write,
+ * but how to implement it without killing performance need more thinking.
+ */
+static int fuse_write_begin(struct file *file, struct address_space *mapping,
+               loff_t pos, unsigned len, unsigned flags,
+               struct page **pagep, void **fsdata)
+{
+       pgoff_t index = pos >> PAGE_CACHE_SHIFT;
+       struct fuse_conn *fc = get_fuse_conn(file->f_dentry->d_inode);
+       struct page *page;
+       loff_t fsize;
+       int err = -ENOMEM;
+
+       WARN_ON(!fc->writeback_cache);
+
+       page = grab_cache_page_write_begin(mapping, index, flags);
+       if (!page)
+               goto error;
+
+       fuse_wait_on_page_writeback(mapping->host, page->index);
+
+       if (PageUptodate(page) || len == PAGE_CACHE_SIZE)
+               goto success;
+       /*
+        * Check if the start this page comes after the end of file, in which
+        * case the readpage can be optimized away.
+        */
+       fsize = i_size_read(mapping->host);
+       if (fsize <= (pos & PAGE_CACHE_MASK)) {
+               size_t off = pos & ~PAGE_CACHE_MASK;
+               if (off)
+                       zero_user_segment(page, 0, off);
+               goto success;
+       }
+       err = fuse_do_readpage(file, page);
+       if (err)
+               goto cleanup;
+success:
+       *pagep = page;
+       return 0;
+
+cleanup:
+       unlock_page(page);
+       page_cache_release(page);
+error:
+       return err;
+}
+
+static int fuse_write_end(struct file *file, struct address_space *mapping,
+               loff_t pos, unsigned len, unsigned copied,
+               struct page *page, void *fsdata)
+{
+       struct inode *inode = page->mapping->host;
+
+       if (!PageUptodate(page)) {
+               /* Zero any unwritten bytes at the end of the page */
+               size_t endoff = (pos + copied) & ~PAGE_CACHE_MASK;
+               if (endoff)
+                       zero_user_segment(page, endoff, PAGE_CACHE_SIZE);
+               SetPageUptodate(page);
+       }
+
+       fuse_write_update_size(inode, pos + copied);
+       set_page_dirty(page);
+       unlock_page(page);
+       page_cache_release(page);
+
+       return copied;
+}
+
 static int fuse_launder_page(struct page *page)
 {
        int err = 0;
@@ -2979,6 +3050,8 @@ static const struct address_space_operations fuse_file_aops  = {
        .set_page_dirty = __set_page_dirty_nobuffers,
        .bmap           = fuse_bmap,
        .direct_IO      = fuse_direct_IO,
+       .write_begin    = fuse_write_begin,
+       .write_end      = fuse_write_end,
 };
 
 void fuse_init_file_inode(struct inode *inode)