> On Nov 14, 2022, at 9:07 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> Ceph has a need to know whether a particular file has any locks set on
> it. It's currently tracking that by a num_locks field in its
> filp->private_data, but that's problematic as it tries to decrement this
> field when releasing locks and that can race with the file being torn
> down.
>
> Add a new vfs_file_has_locks helper that will scan the flock and posix
> lists, and return true if any of the locks have a fl_file that matches
> the given one. Ceph can then call this instead of doing its own
> tracking.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
LGTM.
> ---
> fs/locks.c | 36 ++++++++++++++++++++++++++++++++++++
> include/linux/fs.h | 1 +
> 2 files changed, 37 insertions(+)
>
> Xiubo,
>
> Here's what I was thinking instead of trying to track this within ceph.
> Most inodes never have locks set, so in most cases this will be a NULL
> pointer check.
>
> diff --git a/fs/locks.c b/fs/locks.c
> index 5876c8ff0edc..c7f903b63a53 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -2672,6 +2672,42 @@ int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
> }
> EXPORT_SYMBOL_GPL(vfs_cancel_lock);
>
> +/**
> + * vfs_file_has_locks - are any locks held that were set on @filp?
> + * @filp: open file to check for locks
> + *
> + * Return true if are any FL_POSIX or FL_FLOCK locks currently held
> + * on @filp.
> + */
> +bool vfs_file_has_locks(struct file *filp)
> +{
> + struct file_lock_context *ctx;
> + struct file_lock *fl;
> + bool ret = false;
> +
> + ctx = smp_load_acquire(&locks_inode(filp)->i_flctx);
> + if (!ctx)
> + return false;
> +
> + spin_lock(&ctx->flc_lock);
> + list_for_each_entry(fl, &ctx->flc_posix, fl_list) {
> + if (fl->fl_file == filp) {
> + ret = true;
> + goto out;
> + }
> + }
> + list_for_each_entry(fl, &ctx->flc_flock, fl_list) {
> + if (fl->fl_file == filp) {
> + ret = true;
> + break;
> + }
> + }
> +out:
> + spin_unlock(&ctx->flc_lock);
> + return ret;
> +}
> +EXPORT_SYMBOL(vfs_file_has_locks);
> +
> #ifdef CONFIG_PROC_FS
> #include <linux/proc_fs.h>
> #include <linux/seq_file.h>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index e654435f1651..e4d0f1fa7f9f 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1170,6 +1170,7 @@ extern int locks_delete_block(struct file_lock *);
> extern int vfs_test_lock(struct file *, struct file_lock *);
> extern int vfs_lock_file(struct file *, unsigned int, struct file_lock *, struct file_lock *);
> extern int vfs_cancel_lock(struct file *filp, struct file_lock *fl);
> +bool vfs_file_has_locks(struct file *file);
> extern int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl);
> extern int __break_lease(struct inode *inode, unsigned int flags, unsigned int type);
> extern void lease_get_mtime(struct inode *, struct timespec64 *time);
> --
> 2.38.1
>
--
Chuck Lever
