From patchwork Thu Dec 7 03:20:05 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 10097595 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 7C88C60325 for ; Thu, 7 Dec 2017 03:20:34 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 765A22A26B for ; Thu, 7 Dec 2017 03:20:34 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6AE1A2A26E; Thu, 7 Dec 2017 03:20:34 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_TVD_MIME_EPI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id ED0272A26B for ; Thu, 7 Dec 2017 03:20:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752142AbdLGDUS (ORCPT ); Wed, 6 Dec 2017 22:20:18 -0500 Received: from mx2.suse.de ([195.135.220.15]:45090 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752129AbdLGDUR (ORCPT ); Wed, 6 Dec 2017 22:20:17 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id A2EFEAD6E; Thu, 7 Dec 2017 03:20:15 +0000 (UTC) From: NeilBrown To: Linus Torvalds Date: Thu, 07 Dec 2017 14:20:05 +1100 Cc: Trond Myklebust , Anna Schumaker , Al Viro , Andrew Morton , lkml , "linux-nfs\@vger.kernel.org" , linux-fsdevel , Lennart Poettering Subject: Re: [PATCH] NFS: allow name_to_handle_at() to work for Amazon EFS. In-Reply-To: References: <87po7zv62h.fsf@notabene.neil.brown.name> Message-ID: <87r2s7ql5m.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Wed, Dec 06 2017, Linus Torvalds wrote: > On Thu, Nov 30, 2017 at 12:56 PM, NeilBrown wrote: >> >> -/* limit the handle size to NFSv4 handle size now */ >> -#define MAX_HANDLE_SZ 128 >> +/* Must be larger than NFSv4 file handle, but small >> + * enough for an on-stack allocation. overlayfs doesn't >> + * want this too close to 255. >> + */ >> +#define MAX_HANDLE_SZ 200 > > This really smells for so many reasons. > > Also, that really is starting to be a fairly big stack allocation, and > it seems to be used in exactly one place (show_mark_fhandle), which > makes me go "why is that on the stack anyway?". > > Could we just allocate a buffer at open time or something? > > Linus "open time" would be when /proc/X/fdinfo/Y was opened in seq_fdinfo_open(), and allocating a file_handle there seems a bit odd. We can allocate in fs/notify/fdinfo.c:show_fdinfo() which is the earliest 'notify' specific code to run. There is no opportunity to return an error but GFP_KERNEL allocations under 1 page never fail.. This patch allocates a single buffer for all inodes reported for a given inotify fdinfo, and if the allocation files, the filehandle is silently left blank. More surgery would be needed to be able to return an error. Is that at all suitable? Thanks, NeilBrown From: NeilBrown Subject: fs/notify: don't put file handle buffer on stack. A file handle buffer is not tiny, and could need to be larger in future, so it isn't safe to allocate one on the stack. Instead, we need to kmalloc(). There is no way to return an error status from a ->show_fdinfo() function, so if the kmalloc fails, we silently exclude the filehandle from the output. As it is at the end of line, this shouldn't upset parsing too much. Signed-off-by: NeilBrown diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c index d478629c728b..20d863b9ae16 100644 --- a/fs/notify/fdinfo.c +++ b/fs/notify/fdinfo.c @@ -23,56 +23,58 @@ static void show_fdinfo(struct seq_file *m, struct file *f, void (*show)(struct seq_file *m, - struct fsnotify_mark *mark)) + struct fsnotify_mark *mark, + struct fid *fh)) { struct fsnotify_group *group = f->private_data; struct fsnotify_mark *mark; + struct fid *fh = kmalloc(MAX_HANDLE_SZ, GFP_KERNEL); mutex_lock(&group->mark_mutex); list_for_each_entry(mark, &group->marks_list, g_list) { - show(m, mark); + show(m, mark, fh); if (seq_has_overflowed(m)) break; } mutex_unlock(&group->mark_mutex); + kfree(fh); } #if defined(CONFIG_EXPORTFS) -static void show_mark_fhandle(struct seq_file *m, struct inode *inode) +static void show_mark_fhandle(struct seq_file *m, struct inode *inode, + struct fid *fhbuf) { - struct { - struct file_handle handle; - u8 pad[MAX_HANDLE_SZ]; - } f; int size, ret, i; + unsigned char *bytes; - f.handle.handle_bytes = sizeof(f.pad); - size = f.handle.handle_bytes >> 2; + if (!fhbuf) + return; + size = MAX_HANDLE_SZ >> 2; - ret = exportfs_encode_inode_fh(inode, (struct fid *)f.handle.f_handle, &size, 0); + ret = exportfs_encode_inode_fh(inode, fhbuf, &size, 0); if ((ret == FILEID_INVALID) || (ret < 0)) { WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", ret); return; } - f.handle.handle_type = ret; - f.handle.handle_bytes = size * sizeof(u32); - - seq_printf(m, "fhandle-bytes:%x fhandle-type:%x f_handle:", - f.handle.handle_bytes, f.handle.handle_type); + seq_printf(m, "fhandle-bytes:%zx fhandle-type:%x f_handle:", + size * sizeof(u32), ret); - for (i = 0; i < f.handle.handle_bytes; i++) - seq_printf(m, "%02x", (int)f.handle.f_handle[i]); + bytes = (unsigned char *)(fhbuf->raw); + for (i = 0; i < size * sizeof(u32); i++) + seq_printf(m, "%02x", bytes[i]); } #else -static void show_mark_fhandle(struct seq_file *m, struct inode *inode) +static void show_mark_fhandle(struct seq_file *m, struct inode *inode, + struct fid *fhbuf) { } #endif #ifdef CONFIG_INOTIFY_USER -static void inotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark) +static void inotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark, + struct fid *fhbuf) { struct inotify_inode_mark *inode_mark; struct inode *inode; @@ -93,7 +95,7 @@ static void inotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark) seq_printf(m, "inotify wd:%x ino:%lx sdev:%x mask:%x ignored_mask:%x ", inode_mark->wd, inode->i_ino, inode->i_sb->s_dev, mask, mark->ignored_mask); - show_mark_fhandle(m, inode); + show_mark_fhandle(m, inode, fhbuf); seq_putc(m, '\n'); iput(inode); } @@ -108,7 +110,8 @@ void inotify_show_fdinfo(struct seq_file *m, struct file *f) #ifdef CONFIG_FANOTIFY -static void fanotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark) +static void fanotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark, + struct fid *fhbuf) { unsigned int mflags = 0; struct inode *inode; @@ -123,7 +126,7 @@ static void fanotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark) seq_printf(m, "fanotify ino:%lx sdev:%x mflags:%x mask:%x ignored_mask:%x ", inode->i_ino, inode->i_sb->s_dev, mflags, mark->mask, mark->ignored_mask); - show_mark_fhandle(m, inode); + show_mark_fhandle(m, inode, fhbuf); seq_putc(m, '\n'); iput(inode); } else if (mark->connector->flags & FSNOTIFY_OBJ_TYPE_VFSMOUNT) {