Return-Path: linux-nfs-owner@vger.kernel.org Received: from mx1.redhat.com ([209.132.183.28]:45710 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751874AbaBAN5X (ORCPT ); Sat, 1 Feb 2014 08:57:23 -0500 Date: Sat, 1 Feb 2014 08:57:10 -0500 From: Jeff Layton To: One Thousand Gnomes Cc: Pavel Shilovsky , linux-kernel@vger.kernel.org, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, wine-devel@winehq.org Subject: Re: [PATCH v7 1/7] VFS: Introduce new O_DENY* open flags Message-ID: <20140201085710.4ac69808@tlielax.poochiereds.net> In-Reply-To: <20140117181847.6c1f3831@alan.etchedpixels.co.uk> References: <1389953232-9428-1-git-send-email-piastry@etersoft.ru> <1389953232-9428-2-git-send-email-piastry@etersoft.ru> <20140117181847.6c1f3831@alan.etchedpixels.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, 17 Jan 2014 18:18:47 +0000 One Thousand Gnomes wrote: > > +#define ESHAREDENIED 258 /* File is locked with a sharelock */ > > Have you prepared C library patches to match this ? > > (and why not just use EPERM, it has the meaning you want already) > Tough call... On the one hand, ESHAREDENIED is a distinct error code so an application has the ability to determine what happened when an open or unlink fails. OTOH, a lot of applications won't understand ESHAREDENIED and may barf on it. Those apps might handle EPERM better. I'm not sure what the right approach is there... > > > + * Check to see if there's a share_reservation conflict. LOCK_READ/LOCK_WRITE > > + * tell us whether the reservation allows other readers and writers. > > + */ > > +static int > > +locks_mand_conflict(struct file_lock *caller_fl, struct file_lock *sys_fl) > > +{ > > Shouldn't this also check for CAP_SYS_DAC or some similar permission so > that root can override such a mess (eg to fix full disks in an > emergency) ? > > Agreed. This needs a mechanism that allows you to override it, IMO. CAP_DAC_OVERRIDE doesn't seem quite like the right thing since this isn't dealing with permissions, per-se. A new capability bit may even be warranted. > > + > > + /* > > + * For sharelock mounts if a file was created but not opened, we need > > + * to keep parent i_mutex until we finish the open to prevent races when > > + * somebody opens newly created by us file and locks it with a sharelock > > + * before we open it. > > + */ > > + if (IS_SHARELOCK(dir->d_inode) && error > 0 && *opened & FILE_CREATED) { > > + /* Don't check for write permission, don't truncate */ > > + open_flag &= ~O_TRUNC; > > + will_truncate = false; > > + acc_mode = MAY_OPEN; > > + path_to_nameidata(path, nd); > > + > > + error = may_open(&nd->path, acc_mode, open_flag); > > + if (error) { > > + mutex_unlock(&dir->d_inode->i_mutex); > > + goto out; > > + } > > + file->f_path.mnt = nd->path.mnt; > > + error = finish_open(file, nd->path.dentry, NULL, opened); > > + if (error) { > > + mutex_unlock(&dir->d_inode->i_mutex); > > + if (error == -EOPENSTALE) > > + goto stale_open; > > + goto out; > > + } > > + error = sharelock_lock_file(file); > > + mutex_unlock(&dir->d_inode->i_mutex); > > + if (error) > > + goto exit_fput; > > + goto opened; > > + } > > + > > mutex_unlock(&dir->d_inode->i_mutex); > > What stops the file system changing mount flags via a remount between > these two ? > > > > > if (error <= 0) { > > @@ -3034,6 +3073,18 @@ finish_open_created: > > goto stale_open; > > goto out; > > } > > + > > + if (IS_SHARELOCK(dir->d_inode)) { > > + /* > > + * Lock parent i_mutex to prevent races with sharelocks on > > + * newly created files. > > + */ > > + mutex_lock(&dir->d_inode->i_mutex); > > + error = sharelock_lock_file(file); > > + mutex_unlock(&dir->d_inode->i_mutex); > > + if (error) > > + goto exit_fput; > > + } > > opened: > -- > To unsubscribe from this list: send the line "unsubscribe linux-cifs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Jeff Layton