Re: nfsd changes for 2.6.37

J. Bruce Fields
2010-10-27T14:55:48Z

On Wed, Oct 27, 2010 at 03:46:08PM +0200, Arnd Bergmann wrote:
> On Wednesday 27 October 2010, J. Bruce Fields wrote:
> > On Wed, Oct 27, 2010 at 04:39:24AM -0400, Christoph Hellwig wrote:
> > > Do locks_alloc_lock and initialization of the heap struct file_lock
> > > in the caller. This also avoids an entirely useless copy of the
> > > lock structure. free the passed in structure if we are modifying
> > > an existing lock structure.
> >
> > That sounds good; I'll give it a try.
>
> I've already started, this is what I've come up with. I don't have
> a good way to test it though, and don't know as much as you about this
> code. Feel free to use it as a starting point if you like.
> It does look correct to me, but I'm not very confident in this.

Hm, two problems:
- We introduce the possibility of fcntl(fd, F_SETLEASE, F_UNLCK)
failing with ENOMEM.
- fasync_helper(.,.,1,.) sleeps. Argh.

--b.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>
> diff --git a/fs/locks.c b/fs/locks.c
> index 8b2b6ad..c5ec771 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -162,10 +162,11 @@ EXPORT_SYMBOL_GPL(unlock_flocks);
> static struct kmem_cache *filelock_cache __read_mostly;
>
> /* Allocate an empty lock structure. */
> -static struct file_lock *locks_alloc_lock(void)
> +struct file_lock *locks_alloc_lock(void)
> {
> return kmem_cache_alloc(filelock_cache, GFP_KERNEL);
> }
> +EXPORT_SYMBOL_GPL(locks_alloc_lock);
>
> void locks_release_private(struct file_lock *fl)
> {
> @@ -1365,7 +1366,6 @@ int fcntl_getlease(struct file *filp)
> int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
> {
> struct file_lock *fl, **before, **my_before = NULL, *lease;
> - struct file_lock *new_fl = NULL;
> struct dentry *dentry = filp->f_path.dentry;
> struct inode *inode = dentry->d_inode;
> int error, rdlease_count = 0, wrlease_count = 0;
> @@ -1385,11 +1385,6 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
> lease = *flp;
>
> if (arg != F_UNLCK) {
> - error = -ENOMEM;
> - new_fl = locks_alloc_lock();
> - if (new_fl == NULL)
> - goto out;
> -
> error = -EAGAIN;
> if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
> goto out;
> @@ -1434,23 +1429,19 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
> goto out;
> }
>
> - error = 0;
> if (arg == F_UNLCK)
> - goto out;
> + goto out_unlck;
>
> error = -EINVAL;
> if (!leases_enable)
> goto out;
>
> - locks_copy_lock(new_fl, lease);
> - locks_insert_lock(before, new_fl);
> -
> - *flp = new_fl;
> + locks_insert_lock(before, lease);
> +out_unlck:
> return 0;
>
> out:
> - if (new_fl != NULL)
> - locks_free_lock(new_fl);
> + locks_free_lock(lease);
> return error;
> }
> EXPORT_SYMBOL(generic_setlease);
> @@ -1514,26 +1505,31 @@ EXPORT_SYMBOL_GPL(vfs_setlease);
> */
> int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
> {
> - struct file_lock fl, *flp = &fl;
> + struct file_lock *fl;
> struct inode *inode = filp->f_path.dentry->d_inode;
> int error;
>
> - locks_init_lock(&fl);
> - error = lease_init(filp, arg, &fl);
> - if (error)
> + fl = locks_alloc_lock();
> + if (!fl)
> + return -ENOMEM;
> +
> + locks_init_lock(fl);
> + error = lease_init(filp, arg, fl);
> + if (error) {
> + locks_free_lock(fl);
> return error;
> + }
>
> lock_flocks();
> -
> - error = __vfs_setlease(filp, arg, &flp);
> + error = __vfs_setlease(filp, arg, &fl);
> if (error || arg == F_UNLCK)
> goto out_unlock;
>
> - error = fasync_helper(fd, filp, 1, &flp->fl_fasync);
> + error = fasync_helper(fd, filp, 1, &fl->fl_fasync);
> if (error < 0) {
> /* remove lease just inserted by setlease */
> - flp->fl_type = F_UNLCK | F_INPROGRESS;
> - flp->fl_break_time = jiffies - 10;
> + fl->fl_type = F_UNLCK | F_INPROGRESS;
> + fl->fl_break_time = jiffies - 10;
> time_out_leases(inode);
> goto out_unlock;
> }
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 9019e8e..56347e0 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -2614,7 +2614,7 @@ nfs4_open_delegation(struct svc_fh *fh, struct nfsd4_open *open, struct nfs4_sta
> struct nfs4_delegation *dp;
> struct nfs4_stateowner *sop = stp->st_stateowner;
> int cb_up = atomic_read(&sop->so_client->cl_cb_set);
> - struct file_lock fl, *flp = &fl;
> + struct file_lock *fl;
> int status, flag = 0;
>
> flag = NFS4_OPEN_DELEGATE_NONE;
> @@ -2648,20 +2648,24 @@ nfs4_open_delegation(struct svc_fh *fh, struct nfsd4_open *open, struct nfs4_sta
> flag = NFS4_OPEN_DELEGATE_NONE;
> goto out;
> }
> - locks_init_lock(&fl);
> - fl.fl_lmops = &nfsd_lease_mng_ops;
> - fl.fl_flags = FL_LEASE;
> - fl.fl_type = flag == NFS4_OPEN_DELEGATE_READ? F_RDLCK: F_WRLCK;
> - fl.fl_end = OFFSET_MAX;
> - fl.fl_owner = (fl_owner_t)dp;
> - fl.fl_file = find_readable_file(stp->st_file);
> - BUG_ON(!fl.fl_file);
> - fl.fl_pid = current->tgid;
> + status = -ENOMEM;
> + fl = locks_alloc_lock();
> + if (!fl)
> + goto out;
> + locks_init_lock(fl);
> + fl->fl_lmops = &nfsd_lease_mng_ops;
> + fl->fl_flags = FL_LEASE;
> + fl->fl_type = flag == NFS4_OPEN_DELEGATE_READ? F_RDLCK: F_WRLCK;
> + fl->fl_end = OFFSET_MAX;
> + fl->fl_owner = (fl_owner_t)dp;
> + fl->fl_file = find_readable_file(stp->st_file);
> + BUG_ON(!fl->fl_file);
> + fl->fl_pid = current->tgid;
>
> /* vfs_setlease checks to see if delegation should be handed out.
> * the lock_manager callbacks fl_mylease and fl_change are used
> */
> - if ((status = vfs_setlease(fl.fl_file, fl.fl_type, &flp))) {
> + if ((status = vfs_setlease(fl->fl_file, fl->fl_type, &fl))) {
> dprintk("NFSD: setlease failed [%d], no delegation\n", status);
> unhash_delegation(dp);
> flag = NFS4_OPEN_DELEGATE_NONE;