Re: [PATCH 1/3] fs/locks: F_UNLCK extension for F_OFD_GETLK

[stsp]

Hello,

20.06.2023 15:46, Jeff Layton пишет:
> On Tue, 2023-06-20 at 14:55 +0500, Stas Sergeev wrote:
> > Currently F_UNLCK with F_OFD_GETLK returns -EINVAL.
> > The proposed extension allows to use it for getting the lock
> > information from the particular fd.
> >
> > Signed-off-by: Stas Sergeev <stsp2@xxxxxxxxx>
> >
> > CC: Jeff Layton <jlayton@xxxxxxxxxx>
> > CC: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > CC: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> > CC: Christian Brauner <brauner@xxxxxxxxxx>
> > CC: linux-fsdevel@xxxxxxxxxxxxxxx
> > CC: linux-kernel@xxxxxxxxxxxxxxx
> >
> > ---
> >   fs/locks.c | 23 ++++++++++++++++++++---
> >   1 file changed, 20 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/locks.c b/fs/locks.c
> > index df8b26a42524..210766007e63 100644
> > --- a/fs/locks.c
> > +++ b/fs/locks.c
> > @@ -868,6 +868,21 @@ static bool posix_locks_conflict(struct file_lock *caller_fl,
> >   	return locks_conflict(caller_fl, sys_fl);
> >   }
> >   
> > +/* Determine if lock sys_fl blocks lock caller_fl. Used on xx_GETLK
> > + * path so checks for additional GETLK-specific things like F_UNLCK.
> > + */
> > +static bool posix_test_locks_conflict(struct file_lock *caller_fl,
> > +				      struct file_lock *sys_fl)
> > +{
> > +	/* F_UNLCK checks any locks on the same fd. */
> > +	if (caller_fl->fl_type == F_UNLCK) {
> > +		if (!posix_same_owner(caller_fl, sys_fl))
> > +			return false;
> > +		return locks_overlap(caller_fl, sys_fl);
> > +	}
> > +	return posix_locks_conflict(caller_fl, sys_fl);
> > +}
> > +
> >   /* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
> >    * checking before calling the locks_conflict().
> >    */
> > @@ -901,7 +916,7 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
> >   retry:
> >   	spin_lock(&ctx->flc_lock);
> >   	list_for_each_entry(cfl, &ctx->flc_posix, fl_list) {
> > -		if (!posix_locks_conflict(fl, cfl))
> > +		if (!posix_test_locks_conflict(fl, cfl))
> >   			continue;
> >   		if (cfl->fl_lmops && cfl->fl_lmops->lm_lock_expirable
> >   			&& (*cfl->fl_lmops->lm_lock_expirable)(cfl)) {
> > @@ -2207,7 +2222,8 @@ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock)
> >   	if (fl == NULL)
> >   		return -ENOMEM;
> >   	error = -EINVAL;
> > -	if (flock->l_type != F_RDLCK && flock->l_type != F_WRLCK)
> > +	if (cmd != F_OFD_GETLK && flock->l_type != F_RDLCK
> > +			&& flock->l_type != F_WRLCK)
> >   		goto out;
> >   
> >   	error = flock_to_posix_lock(filp, fl, flock);
> > @@ -2414,7 +2430,8 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock)
> >   		return -ENOMEM;
> >   
> >   	error = -EINVAL;
> > -	if (flock->l_type != F_RDLCK && flock->l_type != F_WRLCK)
> > +	if (cmd != F_OFD_GETLK && flock->l_type != F_RDLCK
> > +			&& flock->l_type != F_WRLCK)
> >   		goto out;
> >   
> >   	error = flock64_to_posix_lock(filp, fl, flock);
> This seems like a reasonable sort of interface to add, particularly for
> the CRIU case.

Just for the record: my own cases are
the remaining 2. CRIU case is not mine
and I haven't talked to CRIU people
about that.


>   Using F_UNLCK for this is a bit kludgey, but adding a new
> constant is probably worse.
>
> I'm willing to take this in with an eye toward v6.6. Are you also
> willing to draft up some manpage patches that detail this new interface?
Sure thing.
As soon as its applied, I'll prepare a man
patch, or should it be done before that point?