On Thu, Aug 20, 2015 at 4:17 AM, Jeff Layton <jlayton@xxxxxxxxxxxxxxx> wrote:
> ...when there are open files to be closed.
>
> When knfsd does an fput(), it gets queued to a list and a workqueue job
> is then scheduled to do the actual __fput work. In the case of knfsd
> closing down the file prior to a REMOVE or RENAME, we really want to
> ensure that those files are closed prior to returning. When there are
> files to be closed, call flush_delayed_fput to ensure this.
>
> There are deadlock possibilities if you call flush_delayed_fput while
> holding locks, however. In the case of nfsd_rename, we don't even do the
> lookups of the dentries to be renamed until we've locked for rename.
>
> Once we've figured out what the target dentry is for a rename, check to
> see whether there are cached open files associated with it. If there
> are, then unwind all of the locking, close them all, and then reattempt
> the rename.
>
> Signed-off-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
> ---
> fs/file_table.c | 1 +
> fs/nfsd/filecache.c | 33 ++++++++++++++++++++++++++++++++-
> fs/nfsd/filecache.h | 1 +
> fs/nfsd/trace.h | 10 +++++++++-
> fs/nfsd/vfs.c | 47 +++++++++++++++++++++++++++++++++++++++--------
> 5 files changed, 82 insertions(+), 10 deletions(-)
>
> diff --git a/fs/file_table.c b/fs/file_table.c
> index 7f9d407c7595..33898e72618c 100644
> --- a/fs/file_table.c
> +++ b/fs/file_table.c
> @@ -257,6 +257,7 @@ void flush_delayed_fput(void)
> {
> delayed_fput(NULL);
> }
> +EXPORT_SYMBOL_GPL(flush_delayed_fput);
>
> static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
>
> diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
> index 4bd683f03b6e..b62942ba6e7b 100644
> --- a/fs/nfsd/filecache.c
> +++ b/fs/nfsd/filecache.c
> @@ -284,6 +284,34 @@ nfsd_file_find_locked(struct inode *inode, unsigned int may_flags,
> }
>
> /**
> + * nfsd_file_is_cached - are there any cached open files for this fh?
> + * @inode: inode of the file to check
> + *
> + * Scan the hashtable for open files that match this fh. Returns true if there
> + * are any, and false if not.
> + */
> +bool
> +nfsd_file_is_cached(struct inode *inode)
> +{
> + bool ret = false;
> + struct nfsd_file *nf;
> + unsigned int hashval = (unsigned int)hash_ptr(inode, NFSD_FILE_HASH_BITS);
> +
> + rcu_read_lock();
> + hlist_for_each_entry_rcu(nf, &nfsd_file_hashtbl[hashval].nfb_head,
> + nf_node) {
> + if (inode == nf->nf_inode) {
> + ret = true;
> + break;
> + }
> + }
> + rcu_read_unlock();
> + trace_nfsd_file_is_cached(hashval, inode, (int)ret);
> + return ret;
> +}
> +
> +
> +/**
> * nfsd_file_close_inode - attempt to forcibly close a nfsd_file
> * @inode: inode of the file to attempt to remove
> *
> @@ -305,7 +333,10 @@ nfsd_file_close_inode(struct inode *inode)
> }
> spin_unlock(&nfsd_file_hashtbl[hashval].nfb_lock);
> trace_nfsd_file_close_inode(hashval, inode, !list_empty(&dispose));
> - nfsd_file_dispose_list(&dispose);
> + if (!list_empty(&dispose)) {
> + nfsd_file_dispose_list(&dispose);
> + flush_delayed_fput();
It looks like flush_delayed_fput() is not exported symbol?
And if flush_delayed_fput() is acceptable, it looks like __fput_sync()
is a better fit, because knfsd would not try to do all the delayed
fput() work, just the dispose list...
Cheers,
Tao
> + }
> }
>
> __be32
> diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
> index 191cdb25aa66..4a873efb7953 100644
> --- a/fs/nfsd/filecache.h
> +++ b/fs/nfsd/filecache.h
> @@ -27,6 +27,7 @@ void nfsd_file_cache_shutdown(void);
> void nfsd_file_put(struct nfsd_file *nf);
> struct nfsd_file *nfsd_file_get(struct nfsd_file *nf);
> void nfsd_file_close_inode(struct inode *inode);
> +bool nfsd_file_is_cached(struct inode *inode);
> __be32 nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> unsigned int may_flags, struct nfsd_file **nfp);
> #endif /* _FS_NFSD_FILECACHE_H */
> diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> index 95af3b9c7b66..fc6d8ee51a00 100644
> --- a/fs/nfsd/trace.h
> +++ b/fs/nfsd/trace.h
> @@ -140,7 +140,7 @@ TRACE_EVENT(nfsd_file_acquire,
> be32_to_cpu(__entry->status))
> );
>
> -TRACE_EVENT(nfsd_file_close_inode,
> +DECLARE_EVENT_CLASS(nfsd_file_search_class,
> TP_PROTO(unsigned int hash, struct inode *inode, int found),
> TP_ARGS(hash, inode, found),
> TP_STRUCT__entry(
> @@ -156,6 +156,14 @@ TRACE_EVENT(nfsd_file_close_inode,
> TP_printk("hash=0x%x inode=0x%p found=%d", __entry->hash,
> __entry->inode, __entry->found)
> );
> +
> +#define DEFINE_NFSD_FILE_SEARCH_EVENT(name) \
> +DEFINE_EVENT(nfsd_file_search_class, name, \
> + TP_PROTO(unsigned int hash, struct inode *inode, int found), \
> + TP_ARGS(hash, inode, found))
> +
> +DEFINE_NFSD_FILE_SEARCH_EVENT(nfsd_file_close_inode);
> +DEFINE_NFSD_FILE_SEARCH_EVENT(nfsd_file_is_cached);
> #endif /* _NFSD_TRACE_H */
>
> #undef TRACE_INCLUDE_PATH
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 98d3b9d96480..4cc78a4ec694 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -1592,6 +1592,17 @@ nfsd_close_cached_files(struct dentry *dentry)
> nfsd_file_close_inode(inode);
> }
>
> +static bool
> +nfsd_has_cached_files(struct dentry *dentry)
> +{
> + bool ret = false;
> + struct inode *inode = d_inode(dentry);
> +
> + if (inode && S_ISREG(inode->i_mode))
> + ret = nfsd_file_is_cached(inode);
> + return ret;
> +}
> +
> /*
> * Rename a file
> * N.B. After this call _both_ ffhp and tfhp need an fh_put
> @@ -1604,6 +1615,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
> struct inode *fdir, *tdir;
> __be32 err;
> int host_err;
> + bool has_cached = false;
>
> err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_REMOVE);
> if (err)
> @@ -1622,6 +1634,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
> if (!flen || isdotent(fname, flen) || !tlen || isdotent(tname, tlen))
> goto out;
>
> +retry:
> host_err = fh_want_write(ffhp);
> if (host_err) {
> err = nfserrno(host_err);
> @@ -1661,12 +1674,16 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
> if (ffhp->fh_export->ex_path.dentry != tfhp->fh_export->ex_path.dentry)
> goto out_dput_new;
>
> - nfsd_close_cached_files(ndentry);
> - host_err = vfs_rename(fdir, odentry, tdir, ndentry, NULL, 0);
> - if (!host_err) {
> - host_err = commit_metadata(tfhp);
> - if (!host_err)
> - host_err = commit_metadata(ffhp);
> + if (nfsd_has_cached_files(ndentry)) {
> + has_cached = true;
> + goto out_dput_old;
> + } else {
> + host_err = vfs_rename(fdir, odentry, tdir, ndentry, NULL, 0);
> + if (!host_err) {
> + host_err = commit_metadata(tfhp);
> + if (!host_err)
> + host_err = commit_metadata(ffhp);
> + }
> }
> out_dput_new:
> dput(ndentry);
> @@ -1679,12 +1696,26 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
> * as that would do the wrong thing if the two directories
> * were the same, so again we do it by hand.
> */
> - fill_post_wcc(ffhp);
> - fill_post_wcc(tfhp);
> + if (!has_cached) {
> + fill_post_wcc(ffhp);
> + fill_post_wcc(tfhp);
> + }
> unlock_rename(tdentry, fdentry);
> ffhp->fh_locked = tfhp->fh_locked = 0;
> fh_drop_write(ffhp);
>
> + /*
> + * If the target dentry has cached open files, then we need to try to
> + * close them prior to doing the rename. Flushing delayed fput
> + * shouldn't be done with locks held however, so we delay it until this
> + * point and then reattempt the whole shebang.
> + */
> + if (has_cached) {
> + has_cached = false;
> + nfsd_close_cached_files(ndentry);
> + dput(ndentry);
> + goto retry;
> + }
> out:
> return err;
> }
> --
> 2.4.3
>
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