Hi,
On Wed, Aug 16, 2023 at 9:07 AM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> On Mon, 2023-08-14 at 17:11 -0400, Alexander Aring wrote:
> > This patch uses the FL_SLEEP flag in struct file_lock to check if it's a
> > blocking request in case if the request coming from nfs lockd process
> > indicated by lm_grant() is set.
> >
> > IF FL_SLEEP is set a asynchronous blocking request is being made and
> > it's waiting for lm_grant() callback being called to signal the lock was
> > granted. If it's not set a synchronous non-blocking request is being made.
> >
> > Signed-off-by: Alexander Aring <aahringo@xxxxxxxxxx>
> > ---
> > fs/dlm/plock.c | 38 ++++++++++++++++++++++----------------
> > 1 file changed, 22 insertions(+), 16 deletions(-)
> >
> > diff --git a/fs/dlm/plock.c b/fs/dlm/plock.c
> > index 0094fa4004cc..524771002a2f 100644
> > --- a/fs/dlm/plock.c
> > +++ b/fs/dlm/plock.c
> > @@ -140,7 +140,6 @@ int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
> > op->info.optype = DLM_PLOCK_OP_LOCK;
> > op->info.pid = fl->fl_pid;
> > op->info.ex = (fl->fl_type == F_WRLCK);
> > - op->info.wait = IS_SETLKW(cmd);
> > op->info.fsid = ls->ls_global_id;
> > op->info.number = number;
> > op->info.start = fl->fl_start;
> > @@ -148,24 +147,31 @@ int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
> > op->info.owner = (__u64)(long)fl->fl_owner;
> > /* async handling */
> > if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
> > - op_data = kzalloc(sizeof(*op_data), GFP_NOFS);
> > - if (!op_data) {
> > - dlm_release_plock_op(op);
> > - rv = -ENOMEM;
> > - goto out;
> > - }
> > + if (fl->fl_flags & FL_SLEEP) {
> > + op_data = kzalloc(sizeof(*op_data), GFP_NOFS);
> > + if (!op_data) {
> > + dlm_release_plock_op(op);
> > + rv = -ENOMEM;
> > + goto out;
> > + }
> >
> > - op_data->callback = fl->fl_lmops->lm_grant;
> > - locks_init_lock(&op_data->flc);
> > - locks_copy_lock(&op_data->flc, fl);
> > - op_data->fl = fl;
> > - op_data->file = file;
> > + op->info.wait = 1;
> > + op_data->callback = fl->fl_lmops->lm_grant;
> > + locks_init_lock(&op_data->flc);
> > + locks_copy_lock(&op_data->flc, fl);
> > + op_data->fl = fl;
> > + op_data->file = file;
> >
> > - op->data = op_data;
> > + op->data = op_data;
> >
> > - send_op(op);
> > - rv = FILE_LOCK_DEFERRED;
> > - goto out;
> > + send_op(op);
> > + rv = FILE_LOCK_DEFERRED;
> > + goto out;
>
> A question...we're returning FILE_LOCK_DEFERRED after the DLM request is
> sent. If it ends up being blocked, what happens? Does it do a lm_grant
> downcall with -EAGAIN or something as the result?
>
no, when info->wait is set then it is a blocked lock request, which
means lm_grant() will be called when the lock request is granted.
>
> > + } else {
> > + op->info.wait = 0;
> > + }
> > + } else {
> > + op->info.wait = IS_SETLKW(cmd);
> > }
> >
> > send_op(op);
>
> Looks reasonable overall.
>
> Now that I look, we have quite a number of places in the kernel that
> seem to check for F_SETLKW, when what they really want is to check
> FL_SLEEP.
Yes, so far I understand FL_SLEEP is F_SETLKW when you get only
F_SETLK in case of fl->fl_lmops && fl->fl_lmops->lm_grant is true. It
is confusing but this is how it works... if it's not set we will get
F_SETLKW and this should imply FL_SLEEP is set.
- Alex
