Return-Path: Received: from mail-yk0-f175.google.com ([209.85.160.175]:35849 "EHLO mail-yk0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752193AbbHULVX (ORCPT ); Fri, 21 Aug 2015 07:21:23 -0400 Received: by ykfw73 with SMTP id w73so66655681ykf.3 for ; Fri, 21 Aug 2015 04:21:22 -0700 (PDT) Date: Fri, 21 Aug 2015 07:21:18 -0400 From: Jeff Layton To: Peng Tao Cc: Bruce Fields , Linux NFS Mailing List , Christoph Hellwig , Kinglong Mee Subject: Re: [PATCH v3 15/20] nfsd: call flush_delayed_fput from nfsd_file_close_fh Message-ID: <20150821072118.6c3a65b2@tlielax.poochiereds.net> In-Reply-To: References: <1440069440-27454-1-git-send-email-jeff.layton@primarydata.com> <1440069440-27454-16-git-send-email-jeff.layton@primarydata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, 20 Aug 2015 19:18:25 -0700 Peng Tao wrote: > On Thu, Aug 20, 2015 at 6:01 PM, Peng Tao wrote: > > On Thu, Aug 20, 2015 at 4:17 AM, Jeff Layton 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 > >> --- > >> 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... > oh, just saw that flush_delayed_fput() is exported in this patch! > sorry for the noise. But I still think __fput_sync() might be a better > fit, despite the assertion there... I'm fine with settling with > flush_delayed_fput() though since calling __fput_sync() from a kernel > thread might get more objections. > > Cheers, > Tao > I looked at __fput_sync when I first rolled this patch, but it's a little less convenient to use. __fput_sync is a synchronous analogue to fput -- so you have to ensure that you use it instead of fput. To make that work here, we'd need a separate set of destruction routines that uses __fput_sync instead of fput. Certainly we can do that if necessary, but I don't think it's really worth it. The downside of course is that we might end up with this thread doing a little extra __fput work if there happened to be other things queued onto the delayed_fput_list, but I'm not too concerned about that. > > > > 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 > >> > >> -- > >> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > >> the body of a message to majordomo@vger.kernel.org > >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- Jeff Layton