Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754685Ab0DSMaH (ORCPT ); Mon, 19 Apr 2010 08:30:07 -0400 Received: from cantor2.suse.de ([195.135.220.15]:47985 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751440Ab0DSMaE (ORCPT ); Mon, 19 Apr 2010 08:30:04 -0400 Date: Mon, 19 Apr 2010 14:30:03 +0200 From: Jan Blunck To: Frederic Weisbecker Cc: Ingo Molnar , LKML , Arnd Bergmann , Thomas Gleixner , Al Viro Subject: Re: [GIT PULL] Preparation for BKL'ed ioctl removal Message-ID: <20100419123003.GE10776@bolzano.suse.de> References: <1271390105-20355-1-git-send-regression-fweisbec@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1271390105-20355-1-git-send-regression-fweisbec@gmail.com> Organization: SUSE LINUX Products GmbH, GF Markus Rex, HRB 16746 (AG Nuernberg) User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6658 Lines: 187 On Fri, Apr 16, Frederic Weisbecker wrote: > Linus, > > In order to stop the bkl contagion in ioctl and push the > bkl from Vfs to the drivers that don't implement a proper > unlock_ioctl, this patch proposes to add a new "locked_ioctl" > field in struct file_operation. > > This field is never called from vfs and requires to assign a > new "deprecated_ioctl" helper to the unlocked_ioctl field. > This deprecated_ioctl() helper then calls the locked_ioctl() > callback with the bkl held. > > The point of doing this is to change every users of fops::ioctl > to the new scheme. Once there is no more users of the ioctl field, > we'll then be able to remove it. > > Also this change brings a new config BKL which is always > enabled for now. Every drivers that use the bkl through > explicit lock_kernel() calls or by using deprecated_ioctl() > will have to select CONFIG_BKL. > > Once we get no more uses of the bkl from the core features but > only on individual drivers, config BKL can be turned off > by default and selected by those drivers if needed, relegating > the bkl as an obsolete library for poor old drivers. > > And given the work happening currently (tty mutex, vfs pushdowns, > procfs bkl removal, llseek janitorials, etc...), this may happen > sooner than was expected. > > Now the point of having this patch in 2.6.34 is to turn > the old ioctl implementations to the new scheme in a set > of patches that relevant maintainers can apply to their > tree (or apply by ourself for unmaintained areas) for .35 > Otherwise we would need to queue everything in a single > tree that may bring conflicts in the next merge window. > > This single patch has very few chances to bring any regressions. > > Please pull the bkl/ioctl branch that can be found at: > > git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing.git > bkl/ioctl > > Thanks, > Frederic > --- > > Arnd Bergmann (1): > vfs: Introduce CONFIG_BKL and deprecated_ioctl > > > fs/ioctl.c | 22 ++++++++++++++++++++++ > include/linux/fs.h | 3 +++ > include/linux/smp_lock.h | 4 ++++ > kernel/Kconfig.locks | 10 ++++++++++ > 4 files changed, 39 insertions(+), 0 deletions(-) > > --- > commit 588a2267f7b2919ae73380e0932cc6a202787036 > Author: Arnd Bergmann > Date: Thu Apr 1 14:42:38 2010 +0200 > > vfs: Introduce CONFIG_BKL and deprecated_ioctl > > This is a preparation for the removal of the big kernel lock that > introduces new interfaces for device drivers still using it. > > We can start marking those device drivers as 'depends on CONFIG_BKL' > now, and make that symbol optional later, when the point has come > at which we are able to build a kernel without the BKL. > > Similarly, device drivers that currently make use of the implicit > BKL locking around the ioctl function can now get annotated by > changing > > .ioctl = foo_ioctl, > > to > > .locked_ioctl = foo_ioctl, > .unlocked_ioctl = deprecated_ioctl, > > As soon as no driver remains using the old ioctl callback, it can > get removed. > > [fweisbec: move config bkl from Kconfig.debug to Kconfig.locks, > rename default_ioctl to deprecated_ioctl] > > Signed-off-by: Arnd Bergmann > Signed-off-by: Frederic Weisbecker > > diff --git a/fs/ioctl.c b/fs/ioctl.c > index 6c75110..e6d6a75 100644 > --- a/fs/ioctl.c > +++ b/fs/ioctl.c > @@ -58,6 +58,28 @@ static long vfs_ioctl(struct file *filp, unsigned int cmd, > return error; > } > > +#ifdef CONFIG_BKL > +/* > + * deprecated_ioctl - call locked_ioctl with BKL held > + * > + * Setting only the ioctl operation but not unlocked_ioctl will become > + * invalid in the future, all drivers that are not converted to unlocked_ioctl > + * should set .unlocked_ioctl = deprecated_ioctl now. > + */ > +long deprecated_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) > +{ > + int error = -ENOTTY; > + if (filp->f_op->locked_ioctl) { > + lock_kernel(); > + error = filp->f_op->locked_ioctl(filp->f_path.dentry->d_inode, > + filp, cmd, arg); > + unlock_kernel(); > + } > + return error; > +} > +EXPORT_SYMBOL_GPL(default_ioctl); > +#endif > + > static int ioctl_fibmap(struct file *filp, int __user *p) > { > struct address_space *mapping = filp->f_mapping; > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 39d57bc..6b65b26 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -1492,6 +1492,9 @@ struct file_operations { > int (*readdir) (struct file *, void *, filldir_t); > unsigned int (*poll) (struct file *, struct poll_table_struct *); > int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long); > +#ifdef CONFIG_BKL > + int (*locked_ioctl) (struct inode *, struct file *, unsigned int, unsigned long); > +#endif > long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); > long (*compat_ioctl) (struct file *, unsigned int, unsigned long); > int (*mmap) (struct file *, struct vm_area_struct *); > diff --git a/include/linux/smp_lock.h b/include/linux/smp_lock.h > index 2ea1dd1..c8693e1 100644 > --- a/include/linux/smp_lock.h > +++ b/include/linux/smp_lock.h > @@ -62,4 +62,8 @@ static inline void cycle_kernel_lock(void) > #define kernel_locked() 1 > > #endif /* CONFIG_LOCK_KERNEL */ > + > +loff_t default_llseek(struct file *file, loff_t offset, int origin); Any specific reason why the default llseek() is in this patch? Jan > +long deprecated_ioctl(struct file *filp, unsigned int cmd, unsigned long arg); > + > #endif /* __LINUX_SMPLOCK_H */ > diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks > index 88c92fb..9a80413 100644 > --- a/kernel/Kconfig.locks > +++ b/kernel/Kconfig.locks > @@ -200,3 +200,13 @@ config INLINE_WRITE_UNLOCK_IRQRESTORE > > config MUTEX_SPIN_ON_OWNER > def_bool SMP && !DEBUG_MUTEXES && !HAVE_DEFAULT_NO_SPIN_MUTEXES > + > +config BKL > + def_bool y > + help > + This is the traditional lock that is used in old code instead > + of proper locking. All drivers that use the BKL should depend > + on this symbol. > + This configuration option will become user-selectable in the > + future, as soon as it is possible to build a kernel without > + it. Regards, Jan -- Jan Blunck -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/