Messages in this thread | | | Date | Mon, 19 Apr 2010 14:52:16 +0200 | From | fweisbec@gmail ... | Subject | Re: [GIT PULL] Preparation for BKL'ed ioctl removal |
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On Mon, Apr 19, 2010 at 02:30:03PM +0200, Jan Blunck wrote: > 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 <arnd@arndb.de> > > 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 <arnd@arndb.de> > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > > > > 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
Because this comes along the same kind of bkl preparation work we want to do. The goal is to isolate default_llseek and deprecated_ioctl and only enable them if CONFIG_BKL.
Hence we want their declaration in smp_lock.h
That said it is probably not needed to get the default_llseek declaration here for this release.
I'm going to make a v2 and resend the pull request. Thanks.
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