On Oct 8, 2014, at 4:46 PM, Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> wrote:
> You cannot call pnfs_put_lseg_async() more than once per lseg, so it
> is really an inappropriate way to deal with a refcount issue.
You’re absolutely right!
> Instead, replace it with a function that decrements the refcount, and
> puts the final 'free' operation (which is incompatible with locks) on
> the work queue.
Thanks, this looks like the right solution.
The good news is that nobody should have been hitting this, as the only file layout
server (that I know of) does stable writes, thus doesn’t use the commit path.
-dros
>
> Cc: Weston Andros Adamson <dros@xxxxxxxxxxxxxxx>
> Fixes: e6cf82d1830f: pnfs: add pnfs_put_lseg_async
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> fs/nfs/filelayout/filelayout.c | 2 +-
> fs/nfs/pnfs.c | 33 +++++++++++++++++++++++++++------
> fs/nfs/pnfs.h | 6 +-----
> 3 files changed, 29 insertions(+), 12 deletions(-)
>
> diff --git a/fs/nfs/filelayout/filelayout.c b/fs/nfs/filelayout/filelayout.c
> index abc5056999d6..46fab1cb455a 100644
> --- a/fs/nfs/filelayout/filelayout.c
> +++ b/fs/nfs/filelayout/filelayout.c
> @@ -1031,7 +1031,7 @@ filelayout_clear_request_commit(struct nfs_page *req,
> }
> out:
> nfs_request_remove_commit_list(req, cinfo);
> - pnfs_put_lseg_async(freeme);
> + pnfs_put_lseg_locked(freeme);
> }
>
> static void
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index 76de7f568119..0a5dda4d85c2 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -361,22 +361,43 @@ pnfs_put_lseg(struct pnfs_layout_segment *lseg)
> }
> EXPORT_SYMBOL_GPL(pnfs_put_lseg);
>
> -static void pnfs_put_lseg_async_work(struct work_struct *work)
> +static void pnfs_free_lseg_async_work(struct work_struct *work)
> {
> struct pnfs_layout_segment *lseg;
> + struct pnfs_layout_hdr *lo;
>
> lseg = container_of(work, struct pnfs_layout_segment, pls_work);
> + lo = lseg->pls_layout;
>
> - pnfs_put_lseg(lseg);
> + pnfs_free_lseg(lseg);
> + pnfs_put_layout_hdr(lo);
> }
>
> -void
> -pnfs_put_lseg_async(struct pnfs_layout_segment *lseg)
> +static void pnfs_free_lseg_async(struct pnfs_layout_segment *lseg)
> {
> - INIT_WORK(&lseg->pls_work, pnfs_put_lseg_async_work);
> + INIT_WORK(&lseg->pls_work, pnfs_free_lseg_async_work);
> schedule_work(&lseg->pls_work);
> }
> -EXPORT_SYMBOL_GPL(pnfs_put_lseg_async);
> +
> +void
> +pnfs_put_lseg_locked(struct pnfs_layout_segment *lseg)
> +{
> + if (!lseg)
> + return;
> +
> + assert_spin_locked(&lseg->pls_layout->plh_inode->i_lock);
> +
> + dprintk("%s: lseg %p ref %d valid %d\n", __func__, lseg,
> + atomic_read(&lseg->pls_refcount),
> + test_bit(NFS_LSEG_VALID, &lseg->pls_flags));
> + if (atomic_dec_and_test(&lseg->pls_refcount)) {
> + struct pnfs_layout_hdr *lo = lseg->pls_layout;
> + pnfs_get_layout_hdr(lo);
> + pnfs_layout_remove_lseg(lo, lseg);
> + pnfs_free_lseg_async(lseg);
> + }
> +}
> +EXPORT_SYMBOL_GPL(pnfs_put_lseg_locked);
>
> static u64
> end_offset(u64 start, u64 len)
> diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
> index 509a710148ba..9ae5b765b073 100644
> --- a/fs/nfs/pnfs.h
> +++ b/fs/nfs/pnfs.h
> @@ -190,7 +190,7 @@ extern int nfs4_proc_layoutreturn(struct nfs4_layoutreturn *lrp);
> /* pnfs.c */
> void pnfs_get_layout_hdr(struct pnfs_layout_hdr *lo);
> void pnfs_put_lseg(struct pnfs_layout_segment *lseg);
> -void pnfs_put_lseg_async(struct pnfs_layout_segment *lseg);
> +void pnfs_put_lseg_locked(struct pnfs_layout_segment *lseg);
>
> void set_pnfs_layoutdriver(struct nfs_server *, const struct nfs_fh *, u32);
> void unset_pnfs_layoutdriver(struct nfs_server *);
> @@ -445,10 +445,6 @@ static inline void pnfs_put_lseg(struct pnfs_layout_segment *lseg)
> {
> }
>
> -static inline void pnfs_put_lseg_async(struct pnfs_layout_segment *lseg)
> -{
> -}
> -
> static inline int pnfs_return_layout(struct inode *ino)
> {
> return 0;
> --
> 1.9.3
>
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