On Jun. 14, 2010, 21:46 -0400, Fred Isaman <iisaman@xxxxxxxxxx> wrote:
> The check on list empty before destroying a layout has always bothered me.
> Get rid of it by having lsegs take a reference on their backpointer.
OK, that should work and be somewhat cleaner than what we have today.
Please see notes below...
>
> Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxx>
> ---
> fs/nfs/pnfs.c | 36 +++++++++++++++++++++++++-----------
> 1 files changed, 25 insertions(+), 11 deletions(-)
>
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index 924e6fd..21192b6 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -348,19 +348,27 @@ put_layout(struct pnfs_layout_type *lo)
> BUG_ON_UNLOCKED_LO(lo);
> BUG_ON(lo->refcount <= 0);
>
> - if (--lo->refcount == 0 && list_empty(&lo->segs)) {
> + lo->refcount--;
> +
> + if (lo->refcount > 1)
> + return;
> +
> + /* Make sure is removed from inode list */
> + clp = NFS_SERVER(&nfsi->vfs_inode)->nfs_client;
> + spin_lock(&clp->cl_lock);
> + if (!list_empty(&lo->lo_layouts)) {
> + list_del_init(&lo->lo_layouts);
> + lo->refcount--;
> + }
> + spin_unlock(&clp->cl_lock);
This is awkward.
If we're already doing this overhaul the right thing to do
is separate out listing/unlisting of the layout on the clp list
so that the lo is added to the clp list when its lo->segs list
goes from empty to not empty (and in this case get_layout can be called
as you did as there's a reference from the clp to the lo)
and when its segs list empties it should be unlisted and
put_layout(), then if its refcount will go back to 0
it can be destroyed.
> +
> + if (lo->refcount == 0) {
In this case I'd like to add a
WARN_ON(!list_empty(&lo->segs))
to make sure that the refcounting agrees with the list manipulation.
Thanks!
Benny
> struct layoutdriver_io_operations *io_ops =
> PNFS_LD_IO_OPS(lo);
>
> dprintk("%s: freeing layout %p\n", __func__, lo->ld_data);
> io_ops->free_layout(lo->ld_data);
> lo->ld_data = NULL;
> -
> - /* Unlist the layout. */
> - clp = NFS_SERVER(&nfsi->vfs_inode)->nfs_client;
> - spin_lock(&clp->cl_lock);
> - list_del_init(&lo->lo_layouts);
> - spin_unlock(&clp->cl_lock);
> }
> }
>
> @@ -404,6 +412,7 @@ init_lseg(struct pnfs_layout_type *lo, struct pnfs_layout_segment *lseg)
> kref_init(&lseg->kref);
> lseg->valid = true;
> lseg->layout = lo;
> + get_layout(lo);
> }
>
> static void
> @@ -413,6 +422,7 @@ destroy_lseg(struct kref *kref)
> container_of(kref, struct pnfs_layout_segment, kref);
>
> dprintk("--> %s\n", __func__);
> + put_layout(lseg->layout);
> PNFS_LD_IO_OPS(lseg->layout)->free_lseg(lseg);
> }
>
> @@ -897,9 +907,10 @@ alloc_init_layout(struct inode *ino)
> void *ld_data;
> struct pnfs_layout_type *lo;
> struct layoutdriver_io_operations *io_ops;
> + struct nfs_inode *nfsi = NFS_I(ino);
>
> io_ops = NFS_SERVER(ino)->pnfs_curr_ld->ld_io_ops;
> - lo = &NFS_I(ino)->layout;
> + lo = &nfsi->layout;
> ld_data = io_ops->alloc_layout(ino);
> if (!ld_data) {
> printk(KERN_ERR
> @@ -908,11 +919,13 @@ alloc_init_layout(struct inode *ino)
> return NULL;
> }
>
> + spin_lock(&nfsi->lo_lock);
> BUG_ON(lo->ld_data != NULL);
> lo->ld_data = ld_data;
> memset(&lo->stateid, 0, NFS4_STATEID_SIZE);
> lo->refcount = 1;
> lo->roc_iomode = 0;
> + spin_unlock(&nfsi->lo_lock);
> return lo;
> }
>
> @@ -970,8 +983,10 @@ get_lock_alloc_layout(struct inode *ino)
> spin_lock(&nfsi->lo_lock);
>
> spin_lock(&clp->cl_lock);
> - if (list_empty(&lo->lo_layouts))
> + if (list_empty(&lo->lo_layouts)) {
> list_add_tail(&lo->lo_layouts, &clp->cl_layouts);
> + get_layout(lo);
> + }
> spin_unlock(&clp->cl_lock);
> } else
> lo = ERR_PTR(-ENOMEM);
> @@ -1259,14 +1274,13 @@ pnfs_layout_process(struct nfs4_pnfs_layoutget *lgp)
> goto out;
> }
>
> + spin_lock(&nfsi->lo_lock);
> init_lseg(lo, lseg);
> lseg->range = res->lseg;
> if (lgp->lsegpp) {
> get_lseg(lseg);
> *lgp->lsegpp = lseg;
> }
> -
> - spin_lock(&nfsi->lo_lock);
> pnfs_insert_layout(lo, lseg);
>
> if (res->return_on_close) {
--
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