On Tue, 2010-12-21 at 23:00 -0500, Fred Isaman wrote:
> This is to prepare the way for sensible io draining. Instead of just
> removing the lseg from the list, we instead clear the VALID flag
> (preventing new io from grabbing references to the lseg) and remove
> the reference holding it in the list. Thus the lseg will be removed
> once any io in progress completes and any references still held are
> dropped.
>
> Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxx>
> ---
> fs/nfs/inode.c | 2 +-
> fs/nfs/pnfs.c | 121 ++++++++++++++++++++++++++++++++++++-------------------
> fs/nfs/pnfs.h | 8 +++-
> 3 files changed, 87 insertions(+), 44 deletions(-)
>
> diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
> index e67e31c..43a69da 100644
> --- a/fs/nfs/inode.c
> +++ b/fs/nfs/inode.c
> -/* Called without i_lock held, as the free_lseg call may sleep */
> -static void
> -destroy_lseg(struct kref *kref)
> +static void free_lseg(struct pnfs_layout_segment *lseg)
> {
> - struct pnfs_layout_segment *lseg =
> - container_of(kref, struct pnfs_layout_segment, pls_refcount);
> struct inode *ino = lseg->pls_layout->plh_inode;
>
> - dprintk("--> %s\n", __func__);
> + BUG_ON(atomic_read(&lseg->pls_refcount) != 0);
> NFS_SERVER(ino)->pnfs_curr_ld->free_lseg(lseg);
> /* Matched by get_layout_hdr in pnfs_insert_layout */
> put_layout_hdr(ino);
> }
<snip>
> static void
> -pnfs_free_lseg_list(struct list_head *tmp_list)
> +pnfs_free_lseg_list(struct list_head *free_me)
> {
> - struct pnfs_layout_segment *lseg;
> + struct pnfs_layout_segment *lseg, *tmp;
>
> - while (!list_empty(tmp_list)) {
> - lseg = list_entry(tmp_list->next, struct pnfs_layout_segment,
> - pls_list);
> - dprintk("%s calling put_lseg on %p\n", __func__, lseg);
> - list_del(&lseg->pls_list);
> - put_lseg(lseg);
> - }
> + list_for_each_entry_safe(lseg, tmp, free_me, pls_list)
> + free_lseg(lseg);
> + INIT_LIST_HEAD(free_me);
> }
The above looks very dubious to me. Why is this change needed, and what
guarantees do we have that free_lseg() will do the right thing w.r.t.
removing stuff from the list?
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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