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Date: Fri, 20 Oct 2017 15:48:46 +0300
From: Amir Goldstein <amir73il@...il.com>
To: Miklos Szeredi <mszeredi@...hat.com>
Cc: linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Jan Kara <jack@...e.cz>, Xiong Zhou <xzhou@...hat.com>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] fsnotify: clean up fsnotify()
On Thu, Oct 19, 2017 at 4:58 PM, Miklos Szeredi <mszeredi@...hat.com> wrote:
> Use helpers to get first and next marks from connector.
>
> Also get rid of inode_node/vfsmount_node local variables, which just refers
> to the same objects as iter_info. There was an srcu_dereference() for
> foo_node, but that's completely superfluous since we've already done it
> when obtaining foo_node.
>
> Also get rid of inode_group/vfsmount_group local variables; checking
> against non-NULL for these is the same as checking against non-NULL
> inode_mark/vfsmount_mark.
>
Nice Cleanup!
> Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
> ---
> fs/notify/fsnotify.c | 107 +++++++++++++++++++++++----------------------------
> 1 file changed, 48 insertions(+), 59 deletions(-)
>
> diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
> index 0ab6a7179e4d..7490edd74883 100644
> --- a/fs/notify/fsnotify.c
> +++ b/fs/notify/fsnotify.c
> @@ -243,6 +243,28 @@ static int send_to_group(struct inode *to_tell,
> file_name, cookie, iter_info);
> }
>
> +static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
> +{
> + struct fsnotify_mark_connector *conn;
> + struct hlist_node *node = NULL;
> +
> + conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
> + if (conn)
> + node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);
> +
> + return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
> +}
> +
> +static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark)
> +{
> + struct hlist_node *node = NULL;
> +
> + if (mark)
> + node = srcu_dereference(mark->obj_list.next, &fsnotify_mark_srcu);
> +
> + return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
> +}
> +
> /*
> * This is the main call to fsnotify. The VFS calls into hook specific functions
> * in linux/fsnotify.h. Those functions then in turn call here. Here will call
> @@ -252,11 +274,7 @@ static int send_to_group(struct inode *to_tell,
> int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
> const unsigned char *file_name, u32 cookie)
> {
> - struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
> - struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
> - struct fsnotify_group *inode_group, *vfsmount_group;
> - struct fsnotify_mark_connector *inode_conn, *vfsmount_conn;
> - struct fsnotify_iter_info iter_info;
> + struct fsnotify_iter_info iter_info = { NULL, NULL };
There was a series of security patches converting those initializers to { }
don't ask me why.
> struct mount *mnt;
> int ret = 0;
> /* global tests shouldn't care about events on child only the specific event */
> @@ -291,26 +309,13 @@ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
>
> if ((mask & FS_MODIFY) ||
> (test_mask & to_tell->i_fsnotify_mask)) {
> - inode_conn = srcu_dereference(to_tell->i_fsnotify_marks,
> - &fsnotify_mark_srcu);
> - if (inode_conn)
> - inode_node = srcu_dereference(inode_conn->list.first,
> - &fsnotify_mark_srcu);
> + iter_info.inode_mark = fsnotify_first_mark(&to_tell->i_fsnotify_marks);
> }
>
> if (mnt && ((mask & FS_MODIFY) ||
> (test_mask & mnt->mnt_fsnotify_mask))) {
> - inode_conn = srcu_dereference(to_tell->i_fsnotify_marks,
> - &fsnotify_mark_srcu);
> - if (inode_conn)
> - inode_node = srcu_dereference(inode_conn->list.first,
> - &fsnotify_mark_srcu);
> - vfsmount_conn = srcu_dereference(mnt->mnt_fsnotify_marks,
> - &fsnotify_mark_srcu);
> - if (vfsmount_conn)
> - vfsmount_node = srcu_dereference(
> - vfsmount_conn->list.first,
> - &fsnotify_mark_srcu);
> + iter_info.inode_mark = fsnotify_first_mark(&to_tell->i_fsnotify_marks);
> + iter_info.vfsmount_mark = fsnotify_first_mark(&mnt->mnt_fsnotify_marks);
> }
>
> /*
> @@ -318,41 +323,28 @@ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
> * ignore masks are properly reflected for mount mark notifications.
> * That's why this traversal is so complicated...
> */
> - while (inode_node || vfsmount_node) {
> - inode_group = NULL;
> - inode_mark = NULL;
> - vfsmount_group = NULL;
> - vfsmount_mark = NULL;
> -
> - if (inode_node) {
> - inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
> - struct fsnotify_mark, obj_list);
> - inode_group = inode_mark->group;
> - if (!(inode_mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED))
> - goto skip_inode;
> - }
> + while (iter_info.inode_mark || iter_info.vfsmount_mark) {
> + struct fsnotify_mark *inode_mark = iter_info.inode_mark;
> + struct fsnotify_mark *vfsmount_mark = iter_info.vfsmount_mark;
>
> - if (vfsmount_node) {
> - vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu),
> - struct fsnotify_mark, obj_list);
> - vfsmount_group = vfsmount_mark->group;
> - if (!(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED))
> - goto skip_vfsmount;
> + if (inode_mark &&
> + !(inode_mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
> + vfsmount_mark = NULL;
> + goto skip;
> + }
> + if (vfsmount_mark &&
> + !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
> + inode_mark = NULL;
> + goto skip;
> }
>
> - iter_info.inode_mark = inode_mark;
> - iter_info.vfsmount_mark = vfsmount_mark;
> -
> - if (inode_group && vfsmount_group) {
> - int cmp = fsnotify_compare_groups(inode_group,
> - vfsmount_group);
> - if (cmp > 0) {
> - inode_group = NULL;
> + if (inode_mark && vfsmount_mark) {
> + int cmp = fsnotify_compare_groups(inode_mark->group,
> + vfsmount_mark->group);
> + if (cmp > 0)
> inode_mark = NULL;
> - } else if (cmp < 0) {
> - vfsmount_group = NULL;
> + else if (cmp < 0)
> vfsmount_mark = NULL;
> - }
> }
>
> ret = send_to_group(to_tell, inode_mark, vfsmount_mark, mask,
> @@ -361,14 +353,11 @@ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
>
> if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
> goto out;
> -skip_inode:
> - if (inode_group)
> - inode_node = srcu_dereference(inode_node->next,
> - &fsnotify_mark_srcu);
> -skip_vfsmount:
> - if (vfsmount_group)
> - vfsmount_node = srcu_dereference(vfsmount_node->next,
> - &fsnotify_mark_srcu);
> +skip:
> + if (inode_mark)
> + iter_info.inode_mark = fsnotify_next_mark(iter_info.inode_mark);
else if?
> + if (vfsmount_mark)
> + iter_info.vfsmount_mark = fsnotify_next_mark(iter_info.vfsmount_mark);
> }
> ret = 0;
> out:
> --
> 2.5.5
>
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