Re: [RFCv2][PATCH 4/7] fsnotify: encapsulate embedded fsnotify data in a single spot

[Jan Kara]

On Wed 24-06-15 17:16:07, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> 
> Both inodes and vfsmounts have fsnotify data embedded in them.
> The data is always a "mask" and a "mark".  Take those two
> fields and move them in to a new structure: struct fsnotify_head.
> 
> We will shortly be adding a new field to this.
> 
> This also lets us get rid of the ugly #ifdef in 'struct inode'.
> 
> In searching for i_fsnotify_mark, my regex found the fsnotify_mark
> comment about g_list.  I think the comment was wrong and corrected
> it.

Umm, doesn't this grow struct inode due to padding? I'm not sure whether the
compiler is clever enough to leave the first 32-bit variable only 32-bit
aligned when it is inside a struct (at least my quick test seems to show it
isn't)...

								Honza

> 
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: linux-fsdevel@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> ---
> 
>  b/fs/inode.c                         |    4 ++--
>  b/fs/notify/fanotify/fanotify_user.c |    4 ++--
>  b/fs/notify/fsnotify.c               |   12 ++++++------
>  b/fs/notify/inode_mark.c             |   18 +++++++++---------
>  b/fs/notify/inotify/inotify_user.c   |    2 +-
>  b/include/linux/fs.h                 |    6 ++----
>  b/include/linux/fsnotify_backend.h   |    8 ++++----
>  b/include/linux/fsnotify_head.h      |   17 +++++++++++++++++
>  b/kernel/auditsc.c                   |    4 ++--
>  9 files changed, 45 insertions(+), 30 deletions(-)
> 
> diff -puN fs/inode.c~fsnotify_head fs/inode.c
> --- a/fs/inode.c~fsnotify_head	2015-06-24 17:14:35.694159644 -0700
> +++ b/fs/inode.c	2015-06-24 17:14:35.711160408 -0700
> @@ -181,7 +181,7 @@ int inode_init_always(struct super_block
>  #endif
>  
>  #ifdef CONFIG_FSNOTIFY
> -	inode->i_fsnotify_mask = 0;
> +	inode->i_fsnotify.mask = 0;
>  #endif
>  	inode->i_flctx = NULL;
>  	this_cpu_inc(nr_inodes);
> @@ -363,7 +363,7 @@ void inode_init_once(struct inode *inode
>  	address_space_init_once(&inode->i_data);
>  	i_size_ordered_init(inode);
>  #ifdef CONFIG_FSNOTIFY
> -	INIT_HLIST_HEAD(&inode->i_fsnotify_marks);
> +	INIT_HLIST_HEAD(&inode->i_fsnotify.marks);
>  #endif
>  }
>  EXPORT_SYMBOL(inode_init_once);
> diff -puN fs/notify/fanotify/fanotify_user.c~fsnotify_head fs/notify/fanotify/fanotify_user.c
> --- a/fs/notify/fanotify/fanotify_user.c~fsnotify_head	2015-06-24 17:14:35.696159734 -0700
> +++ b/fs/notify/fanotify/fanotify_user.c	2015-06-24 17:14:35.712160453 -0700
> @@ -562,7 +562,7 @@ static int fanotify_remove_inode_mark(st
>  
>  	/* matches the fsnotify_find_inode_mark() */
>  	fsnotify_put_mark(fsn_mark);
> -	if (removed & inode->i_fsnotify_mask)
> +	if (removed & inode->i_fsnotify.mask)
>  		fsnotify_recalc_inode_mask(inode);
>  
>  	return 0;
> @@ -679,7 +679,7 @@ static int fanotify_add_inode_mark(struc
>  	added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
>  	mutex_unlock(&group->mark_mutex);
>  
> -	if (added & ~inode->i_fsnotify_mask)
> +	if (added & ~inode->i_fsnotify.mask)
>  		fsnotify_recalc_inode_mask(inode);
>  
>  	fsnotify_put_mark(fsn_mark);
> diff -puN fs/notify/fsnotify.c~fsnotify_head fs/notify/fsnotify.c
> --- a/fs/notify/fsnotify.c~fsnotify_head	2015-06-24 17:14:35.697159779 -0700
> +++ b/fs/notify/fsnotify.c	2015-06-24 17:14:35.712160453 -0700
> @@ -104,7 +104,7 @@ int __fsnotify_parent(struct path *path,
>  
>  	if (unlikely(!fsnotify_inode_watches_children(p_inode)))
>  		__fsnotify_update_child_dentry_flags(p_inode);
> -	else if (p_inode->i_fsnotify_mask & mask) {
> +	else if (p_inode->i_fsnotify.mask & mask) {
>  		/* we are notifying a parent so come up with the new mask which
>  		 * specifies these are events which came from a child. */
>  		mask |= FS_EVENT_ON_CHILD;
> @@ -210,7 +210,7 @@ int fsnotify(struct inode *to_tell, __u3
>  	 * this type of event.
>  	 */
>  	if (!(mask & FS_MODIFY) &&
> -	    !(test_mask & to_tell->i_fsnotify_mask) &&
> +	    !(test_mask & to_tell->i_fsnotify.mask) &&
>  	    !(mnt && test_mask & mnt->mnt_fsnotify_mask))
>  		return 0;
>  	/*
> @@ -220,22 +220,22 @@ int fsnotify(struct inode *to_tell, __u3
>  	 * SRCU because we have no references to any objects and do not
>  	 * need SRCU to keep them "alive".
>  	 */
> -	if (!to_tell->i_fsnotify_marks.first &&
> +	if (!to_tell->i_fsnotify.marks.first &&
>  	    (!mnt || !mnt->mnt_fsnotify_marks.first))
>  		return 0;
>  
>  	idx = srcu_read_lock(&fsnotify_mark_srcu);
>  
>  	if ((mask & FS_MODIFY) ||
> -	    (test_mask & to_tell->i_fsnotify_mask))
> -		inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
> +	    (test_mask & to_tell->i_fsnotify.mask))
> +		inode_node = srcu_dereference(to_tell->i_fsnotify.marks.first,
>  					      &fsnotify_mark_srcu);
>  
>  	if (mnt && ((mask & FS_MODIFY) ||
>  		    (test_mask & mnt->mnt_fsnotify_mask))) {
>  		vfsmount_node = srcu_dereference(mnt->mnt_fsnotify_marks.first,
>  						 &fsnotify_mark_srcu);
> -		inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
> +		inode_node = srcu_dereference(to_tell->i_fsnotify.marks.first,
>  					      &fsnotify_mark_srcu);
>  	}
>  
> diff -puN fs/notify/inode_mark.c~fsnotify_head fs/notify/inode_mark.c
> --- a/fs/notify/inode_mark.c~fsnotify_head	2015-06-24 17:14:35.699159868 -0700
> +++ b/fs/notify/inode_mark.c	2015-06-24 17:14:35.712160453 -0700
> @@ -31,13 +31,13 @@
>  #include "../internal.h"
>  
>  /*
> - * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
> + * Recalculate the inode->i_fsnotify.mask, or the mask of all FS_* event types
>   * any notifier is interested in hearing for this inode.
>   */
>  void fsnotify_recalc_inode_mask(struct inode *inode)
>  {
>  	spin_lock(&inode->i_lock);
> -	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
> +	inode->i_fsnotify.mask = fsnotify_recalc_mask(&inode->i_fsnotify.marks);
>  	spin_unlock(&inode->i_lock);
>  
>  	__fsnotify_update_child_dentry_flags(inode);
> @@ -56,11 +56,11 @@ void fsnotify_destroy_inode_mark(struct
>  	mark->inode = NULL;
>  
>  	/*
> -	 * this mark is now off the inode->i_fsnotify_marks list and we
> +	 * this mark is now off the inode->i_fsnotify.marks list and we
>  	 * hold the inode->i_lock, so this is the perfect time to update the
> -	 * inode->i_fsnotify_mask
> +	 * inode->i_fsnotify.mask
>  	 */
> -	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
> +	inode->i_fsnotify.mask = fsnotify_recalc_mask(&inode->i_fsnotify.marks);
>  	spin_unlock(&inode->i_lock);
>  }
>  
> @@ -74,7 +74,7 @@ void fsnotify_clear_marks_by_inode(struc
>  	LIST_HEAD(free_list);
>  
>  	spin_lock(&inode->i_lock);
> -	hlist_for_each_entry_safe(mark, n, &inode->i_fsnotify_marks, obj_list) {
> +	hlist_for_each_entry_safe(mark, n, &inode->i_fsnotify.marks, obj_list) {
>  		list_add(&mark->free_list, &free_list);
>  		hlist_del_init_rcu(&mark->obj_list);
>  		fsnotify_get_mark(mark);
> @@ -102,7 +102,7 @@ struct fsnotify_mark *fsnotify_find_inod
>  	struct fsnotify_mark *mark;
>  
>  	spin_lock(&inode->i_lock);
> -	mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
> +	mark = fsnotify_find_mark(&inode->i_fsnotify.marks, group);
>  	spin_unlock(&inode->i_lock);
>  
>  	return mark;
> @@ -153,9 +153,9 @@ int fsnotify_add_inode_mark(struct fsnot
>  
>  	spin_lock(&inode->i_lock);
>  	mark->inode = inode;
> -	ret = fsnotify_add_mark_list(&inode->i_fsnotify_marks, mark,
> +	ret = fsnotify_add_mark_list(&inode->i_fsnotify.marks, mark,
>  				     allow_dups);
> -	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
> +	inode->i_fsnotify.mask = fsnotify_recalc_mask(&inode->i_fsnotify.marks);
>  	spin_unlock(&inode->i_lock);
>  
>  	return ret;
> diff -puN fs/notify/inotify/inotify_user.c~fsnotify_head fs/notify/inotify/inotify_user.c
> --- a/fs/notify/inotify/inotify_user.c~fsnotify_head	2015-06-24 17:14:35.701159959 -0700
> +++ b/fs/notify/inotify/inotify_user.c	2015-06-24 17:14:35.713160498 -0700
> @@ -547,7 +547,7 @@ static int inotify_update_existing_watch
>  		/* more bits in old than in new? */
>  		int dropped = (old_mask & ~new_mask);
>  		/* more bits in this fsn_mark than the inode's mask? */
> -		int do_inode = (new_mask & ~inode->i_fsnotify_mask);
> +		int do_inode = (new_mask & ~inode->i_fsnotify.mask);
>  
>  		/* update the inode with this new fsn_mark */
>  		if (dropped || do_inode)
> diff -puN include/linux/fs.h~fsnotify_head include/linux/fs.h
> --- a/include/linux/fs.h~fsnotify_head	2015-06-24 17:14:35.702160003 -0700
> +++ b/include/linux/fs.h	2015-06-24 17:14:35.710160363 -0700
> @@ -30,6 +30,7 @@
>  #include <linux/lockdep.h>
>  #include <linux/percpu-rwsem.h>
>  #include <linux/blk_types.h>
> +#include <linux/fsnotify_head.h>
>  
>  #include <asm/byteorder.h>
>  #include <uapi/linux/fs.h>
> @@ -660,10 +661,7 @@ struct inode {
>  
>  	__u32			i_generation;
>  
> -#ifdef CONFIG_FSNOTIFY
> -	__u32			i_fsnotify_mask; /* all events this inode cares about */
> -	struct hlist_head	i_fsnotify_marks;
> -#endif
> +	struct fsnotify_head	i_fsnotify;
>  
>  	void			*i_private; /* fs or device private pointer */
>  };
> diff -puN include/linux/fsnotify_backend.h~fsnotify_head include/linux/fsnotify_backend.h
> --- a/include/linux/fsnotify_backend.h~fsnotify_head	2015-06-24 17:14:35.704160093 -0700
> +++ b/include/linux/fsnotify_backend.h	2015-06-24 17:14:35.709160318 -0700
> @@ -212,7 +212,7 @@ struct fsnotify_mark {
>  	 * in kernel that found and may be using this mark. */
>  	atomic_t refcnt;		/* active things looking at this mark */
>  	struct fsnotify_group *group;	/* group this mark is for */
> -	struct list_head g_list;	/* list of marks by group->i_fsnotify_marks
> +	struct list_head g_list;	/* list of marks by group->marks_list
>  					 * Also reused for queueing mark into
>  					 * destroy_list when it's waiting for
>  					 * the end of SRCU period before it can
> @@ -249,11 +249,11 @@ extern u32 fsnotify_get_cookie(void);
>  static inline int fsnotify_inode_watches_children(struct inode *inode)
>  {
>  	/* FS_EVENT_ON_CHILD is set if the inode may care */
> -	if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
> +	if (!(inode->i_fsnotify.mask & FS_EVENT_ON_CHILD))
>  		return 0;
>  	/* this inode might care about child events, does it care about the
>  	 * specific set of events that can happen on a child? */
> -	return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
> +	return inode->i_fsnotify.mask & FS_EVENTS_POSS_ON_CHILD;
>  }
>  
>  /*
> @@ -326,7 +326,7 @@ extern struct fsnotify_event *fsnotify_r
>  
>  /* run all marks associated with a vfsmount and update mnt->mnt_fsnotify_mask */
>  extern void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt);
> -/* run all marks associated with an inode and update inode->i_fsnotify_mask */
> +/* run all marks associated with an inode and update inode->i_fsnotify.mask */
>  extern void fsnotify_recalc_inode_mask(struct inode *inode);
>  extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(struct fsnotify_mark *mark));
>  /* find (and take a reference) to a mark associated with group and inode */
> diff -puN /dev/null include/linux/fsnotify_head.h
> --- /dev/null	2015-06-17 12:44:31.632705131 -0700
> +++ b/include/linux/fsnotify_head.h	2015-06-24 17:14:35.711160408 -0700
> @@ -0,0 +1,17 @@
> +#ifndef __LINUX_FSNOTIFY_HEAD_H
> +#define __LINUX_FSNOTIFY_HEAD_H
> +
> +#include <linux/types.h>
> +
> +/*
> + * This gets embedded in vfsmounts and inodes.
> + */
> +
> +struct fsnotify_head {
> +#ifdef CONFIG_FSNOTIFY
> +	__u32                   mask; /* all events this object cares about */
> +	struct hlist_head       marks;
> +#endif
> +};
> +
> +#endif	/* __LINUX_FSNOTIFY_HEAD_H */
> diff -puN kernel/auditsc.c~fsnotify_head kernel/auditsc.c
> --- a/kernel/auditsc.c~fsnotify_head	2015-06-24 17:14:35.706160183 -0700
> +++ b/kernel/auditsc.c	2015-06-24 17:14:35.714160543 -0700
> @@ -1587,7 +1587,7 @@ static inline void handle_one(const stru
>  	struct audit_tree_refs *p;
>  	struct audit_chunk *chunk;
>  	int count;
> -	if (likely(hlist_empty(&inode->i_fsnotify_marks)))
> +	if (likely(hlist_empty(&inode->i_fsnotify.marks)))
>  		return;
>  	context = current->audit_context;
>  	p = context->trees;
> @@ -1630,7 +1630,7 @@ retry:
>  	seq = read_seqbegin(&rename_lock);
>  	for(;;) {
>  		struct inode *inode = d_backing_inode(d);
> -		if (inode && unlikely(!hlist_empty(&inode->i_fsnotify_marks))) {
> +		if (inode && unlikely(!hlist_empty(&inode->i_fsnotify.marks))) {
>  			struct audit_chunk *chunk;
>  			chunk = audit_tree_lookup(inode);
>  			if (chunk) {
> _
-- 
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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