Re: [PATCH] vfs: change iterate_supers callback to take an int arg instead of a void *

[Jeff Layton]

On Thu, 2018-05-17 at 18:39 +0200, Jan Kara wrote:
> On Thu 17-05-18 11:46:46, Jeff Layton wrote:
> > From: Jeff Layton <jlayton@xxxxxxxxxx>
> > 
> > All of the callback functions for iterate_supers either ignore the
> > opaque argument, or dereference the pointer only to fetch the int
> > to which it points.
> > 
> > Change iterate_supers to pass an opaque int arg to the callback
> > instead of a void pointer.
> > 
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> 
> Hum, I'm not sure if Luis didn't have any plan with the argument in his
> fs-freeze-during-hibernate series. Luis?
> 
> 								Honza
> 

No worries... Al already NAK'ed this over IRC. I'm reworking the patch
to avoid dereferencing in the existing callers, but leave the callback
prototypes intact. I'll send a v2 patch shortly...

Thanks,
Jeff

 
> > ---
> >  fs/drop_caches.c         |  4 ++--
> >  fs/quota/quota.c         |  6 ++----
> >  fs/super.c               |  3 ++-
> >  fs/sync.c                | 32 ++++++++++++++------------------
> >  include/linux/fs.h       |  2 +-
> >  mm/cleancache.c          |  4 ++--
> >  security/selinux/hooks.c |  4 ++--
> >  7 files changed, 25 insertions(+), 30 deletions(-)
> > 
> > diff --git a/fs/drop_caches.c b/fs/drop_caches.c
> > index 82377017130f..1850e7276fdf 100644
> > --- a/fs/drop_caches.c
> > +++ b/fs/drop_caches.c
> > @@ -14,7 +14,7 @@
> >  /* A global variable is a bit ugly, but it keeps the code simple */
> >  int sysctl_drop_caches;
> >  
> > -static void drop_pagecache_sb(struct super_block *sb, void *unused)
> > +static void drop_pagecache_sb(struct super_block *sb, int unused)
> >  {
> >  	struct inode *inode, *toput_inode = NULL;
> >  
> > @@ -52,7 +52,7 @@ int drop_caches_sysctl_handler(struct ctl_table *table, int write,
> >  		static int stfu;
> >  
> >  		if (sysctl_drop_caches & 1) {
> > -			iterate_supers(drop_pagecache_sb, NULL);
> > +			iterate_supers(drop_pagecache_sb, 0);
> >  			count_vm_event(DROP_PAGECACHE);
> >  		}
> >  		if (sysctl_drop_caches & 2) {
> > diff --git a/fs/quota/quota.c b/fs/quota/quota.c
> > index 860bfbe7a07a..5f1e1c494c07 100644
> > --- a/fs/quota/quota.c
> > +++ b/fs/quota/quota.c
> > @@ -46,10 +46,8 @@ static int check_quotactl_permission(struct super_block *sb, int type, int cmd,
> >  	return security_quotactl(cmd, type, id, sb);
> >  }
> >  
> > -static void quota_sync_one(struct super_block *sb, void *arg)
> > +static void quota_sync_one(struct super_block *sb, int type)
> >  {
> > -	int type = *(int *)arg;
> > -
> >  	if (sb->s_qcop && sb->s_qcop->quota_sync &&
> >  	    (sb->s_quota_types & (1 << type)))
> >  		sb->s_qcop->quota_sync(sb, type);
> > @@ -63,7 +61,7 @@ static int quota_sync_all(int type)
> >  		return -EINVAL;
> >  	ret = security_quotactl(Q_SYNC, type, 0, NULL);
> >  	if (!ret)
> > -		iterate_supers(quota_sync_one, &type);
> > +		iterate_supers(quota_sync_one, type);
> >  	return ret;
> >  }
> >  
> > diff --git a/fs/super.c b/fs/super.c
> > index 122c402049a2..30b7490bd049 100644
> > --- a/fs/super.c
> > +++ b/fs/super.c
> > @@ -596,6 +596,7 @@ static void __iterate_supers(void (*f)(struct super_block *))
> >  		__put_super(p);
> >  	spin_unlock(&sb_lock);
> >  }
> > +
> >  /**
> >   *	iterate_supers - call function for all active superblocks
> >   *	@f: function to call
> > @@ -604,7 +605,7 @@ static void __iterate_supers(void (*f)(struct super_block *))
> >   *	Scans the superblock list and calls given function, passing it
> >   *	locked superblock and given argument.
> >   */
> > -void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
> > +void iterate_supers(void (*f)(struct super_block *, int), int arg)
> >  {
> >  	struct super_block *sb, *p = NULL;
> >  
> > diff --git a/fs/sync.c b/fs/sync.c
> > index b54e0541ad89..8c418da67e41 100644
> > --- a/fs/sync.c
> > +++ b/fs/sync.c
> > @@ -68,16 +68,16 @@ int sync_filesystem(struct super_block *sb)
> >  }
> >  EXPORT_SYMBOL(sync_filesystem);
> >  
> > -static void sync_inodes_one_sb(struct super_block *sb, void *arg)
> > +static void sync_inodes_one_sb(struct super_block *sb, int unused)
> >  {
> >  	if (!sb_rdonly(sb))
> >  		sync_inodes_sb(sb);
> >  }
> >  
> > -static void sync_fs_one_sb(struct super_block *sb, void *arg)
> > +static void sync_fs_one_sb(struct super_block *sb, int arg)
> >  {
> >  	if (!sb_rdonly(sb) && sb->s_op->sync_fs)
> > -		sb->s_op->sync_fs(sb, *(int *)arg);
> > +		sb->s_op->sync_fs(sb, arg);
> >  }
> >  
> >  static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
> > @@ -107,14 +107,12 @@ static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
> >   */
> >  void ksys_sync(void)
> >  {
> > -	int nowait = 0, wait = 1;
> > -
> >  	wakeup_flusher_threads(WB_REASON_SYNC);
> > -	iterate_supers(sync_inodes_one_sb, NULL);
> > -	iterate_supers(sync_fs_one_sb, &nowait);
> > -	iterate_supers(sync_fs_one_sb, &wait);
> > -	iterate_bdevs(fdatawrite_one_bdev, NULL);
> > -	iterate_bdevs(fdatawait_one_bdev, NULL);
> > +	iterate_supers(sync_inodes_one_sb, 0);
> > +	iterate_supers(sync_fs_one_sb, 0);
> > +	iterate_supers(sync_fs_one_sb, 1);
> > +	iterate_bdevs(fdatawrite_one_bdev, 0);
> > +	iterate_bdevs(fdatawait_one_bdev, 0);
> >  	if (unlikely(laptop_mode))
> >  		laptop_sync_completion();
> >  }
> > @@ -127,18 +125,16 @@ SYSCALL_DEFINE0(sync)
> >  
> >  static void do_sync_work(struct work_struct *work)
> >  {
> > -	int nowait = 0;
> > -
> >  	/*
> >  	 * Sync twice to reduce the possibility we skipped some inodes / pages
> >  	 * because they were temporarily locked
> >  	 */
> > -	iterate_supers(sync_inodes_one_sb, &nowait);
> > -	iterate_supers(sync_fs_one_sb, &nowait);
> > -	iterate_bdevs(fdatawrite_one_bdev, NULL);
> > -	iterate_supers(sync_inodes_one_sb, &nowait);
> > -	iterate_supers(sync_fs_one_sb, &nowait);
> > -	iterate_bdevs(fdatawrite_one_bdev, NULL);
> > +	iterate_supers(sync_inodes_one_sb, 0);
> > +	iterate_supers(sync_fs_one_sb, 0);
> > +	iterate_bdevs(fdatawrite_one_bdev, 0);
> > +	iterate_supers(sync_inodes_one_sb, 0);
> > +	iterate_supers(sync_fs_one_sb, 0);
> > +	iterate_bdevs(fdatawrite_one_bdev, 0);
> >  	printk("Emergency Sync complete\n");
> >  	kfree(work);
> >  }
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index 760d8da1b6c7..7107d291d853 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -3115,7 +3115,7 @@ extern struct super_block *get_super_exclusive_thawed(struct block_device *bdev)
> >  extern struct super_block *get_active_super(struct block_device *bdev);
> >  extern void drop_super(struct super_block *sb);
> >  extern void drop_super_exclusive(struct super_block *sb);
> > -extern void iterate_supers(void (*)(struct super_block *, void *), void *);
> > +extern void iterate_supers(void (*)(struct super_block *, int), int);
> >  extern void iterate_supers_type(struct file_system_type *,
> >  			        void (*)(struct super_block *, void *), void *);
> >  
> > diff --git a/mm/cleancache.c b/mm/cleancache.c
> > index f7b9fdc79d97..92d27cc10274 100644
> > --- a/mm/cleancache.c
> > +++ b/mm/cleancache.c
> > @@ -34,7 +34,7 @@ static u64 cleancache_failed_gets;
> >  static u64 cleancache_puts;
> >  static u64 cleancache_invalidates;
> >  
> > -static void cleancache_register_ops_sb(struct super_block *sb, void *unused)
> > +static void cleancache_register_ops_sb(struct super_block *sb, int unused)
> >  {
> >  	switch (sb->cleancache_poolid) {
> >  	case CLEANCACHE_NO_BACKEND:
> > @@ -105,7 +105,7 @@ int cleancache_register_ops(const struct cleancache_ops *ops)
> >  	 * until the corresponding ->init_fs has been actually called and
> >  	 * cleancache_ops has been set.
> >  	 */
> > -	iterate_supers(cleancache_register_ops_sb, NULL);
> > +	iterate_supers(cleancache_register_ops_sb, 0);
> >  	return 0;
> >  }
> >  EXPORT_SYMBOL(cleancache_register_ops);
> > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> > index 4cafe6a19167..91c13b72b427 100644
> > --- a/security/selinux/hooks.c
> > +++ b/security/selinux/hooks.c
> > @@ -7138,7 +7138,7 @@ static __init int selinux_init(void)
> >  	return 0;
> >  }
> >  
> > -static void delayed_superblock_init(struct super_block *sb, void *unused)
> > +static void delayed_superblock_init(struct super_block *sb, int unused)
> >  {
> >  	superblock_doinit(sb, NULL);
> >  }
> > @@ -7149,7 +7149,7 @@ void selinux_complete_init(void)
> >  
> >  	/* Set up any superblocks initialized prior to the policy load. */
> >  	printk(KERN_DEBUG "SELinux:  Setting up existing superblocks.\n");
> > -	iterate_supers(delayed_superblock_init, NULL);
> > +	iterate_supers(delayed_superblock_init, 0);
> >  }
> >  
> >  /* SELinux requires early initialization in order to label
> > -- 
> > 2.17.0
> > 
> > 

-- 
Jeff Layton <jlayton@xxxxxxxxxx>