Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:44104 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751968AbdIAQSK (ORCPT ); Fri, 1 Sep 2017 12:18:10 -0400 Date: Fri, 1 Sep 2017 12:18:09 -0400 From: "J. Bruce Fields" To: NeilBrown Cc: linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Trond Myklebust Subject: Re: [PATCH 2/3] fs: hide another detail of delegation logic Message-ID: <20170901161809.GA22140@parsley.fieldses.org> References: <1503697958-6122-1-git-send-email-bfields@redhat.com> <1503697958-6122-3-git-send-email-bfields@redhat.com> <878ti4i9pi.fsf@notabene.neil.brown.name> <20170829214026.GI8822@parsley.fieldses.org> <8760d5hol3.fsf@notabene.neil.brown.name> <20170830170938.GC24373@parsley.fieldses.org> <87wp5kfxi3.fsf@notabene.neil.brown.name> <20170831190531.GA8223@parsley.fieldses.org> <873787fhc5.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <873787fhc5.fsf@notabene.neil.brown.name> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, Sep 01, 2017 at 09:27:54AM +1000, NeilBrown wrote: > On Thu, Aug 31 2017, J. Bruce Fields wrote: > > Only nfsd fills in the "who" field of deleg_break_ctl. But non-nfsd > > users do need to pass a non-NULL delegated_inode. > > Yes, of course... Just to be clear, I've taken your suggestion to pass the nfs4_client instead of the request so we only have to do a comparison in callback. Among other things that should be a safe approach if we ever have non-nfs breakers that want to pass a "who". Patch appended below if you're curious. > So having been wrong about this code twice, I'm starting to get a feel > for what it does and why. I still wonder if there might be a better > approach though. > > You are changing the interface to pass a magic cookie with the meaning > "Don't bother breaking a delegation which matches this magic cookie". > Would it not be better to pass a delegation, and say "Don't bother > breaking this delegation". And if it were a WRITE delegation, that > could be optimised as "don't bother breaking any delegation, I have a > write delegation so I have exclusive access". > > Whenever we call a vfs_* function that will need to break delegations we > have already done the lookup and have the dentry and inode, so finding a > delegation shouldn't be prohibitive. > > nfsd would need to find that delegation, prevent further delegations > being handed out, and check that there aren't already conflicting > delegations. If there are conflicts, recall them. Once there are no > conflicting delegations, make the vfs_ request. The way that we currently serialize setting, unsetting, and breaking delegations is by locks on the delegated inodes which aren't taken till deeper in the vfs code. I guess you're suggesting adding a second mechanism to prevent delegations being given out on the inode. We could add an atomic counter taken by each nfsd breaker while it's in progress. Hrm. --b. > One downside of this is that nfsd delegations would be recalled before > any others, rather than doing them all in parallel. This could be > addressed by calling try_break_deleg() when recalling the nfsd > delegations. > > This approach seems to be half-way between your original attempt that > you described, which is racy, and the attempt you posted which adds the > callback that I don't particularly like. diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index fb15efcc4e08..b50a7492f47f 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -3825,7 +3825,7 @@ nfsd_break_deleg_cb(struct file_lock *fl) return ret; } -static struct nfs4_client *nfsd4_client_from_rqst(struct svc_rqst *rqst) +void *nfsd4_client_from_rqst(struct svc_rqst *rqst) { struct nfsd4_compoundres *resp; @@ -3843,19 +3843,14 @@ static struct nfs4_client *nfsd4_client_from_rqst(struct svc_rqst *rqst) static bool nfsd_breaker_owns_lease(void *who, struct file_lock *fl) { - struct svc_rqst *rqst = who; struct nfs4_client *cl; struct nfs4_delegation *dl; struct nfs4_file *fi = (struct nfs4_file *)fl->fl_owner; bool ret = true; - cl = nfsd4_client_from_rqst(rqst); - if (!cl) - return false; - spin_lock(&fi->fi_lock); list_for_each_entry(dl, &fi->fi_delegations, dl_perfile) { - if (dl->dl_stid.sc_client != cl) { + if (dl->dl_stid.sc_client != who) { ret = false; break; } diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h index b9c538ab7a59..f7819ce6c817 100644 --- a/fs/nfsd/nfsd.h +++ b/fs/nfsd/nfsd.h @@ -125,6 +125,7 @@ void nfs4_reset_lease(time_t leasetime); int nfs4_reset_recoverydir(char *recdir); char * nfs4_recoverydir(void); bool nfsd4_spo_must_allow(struct svc_rqst *rqstp); +void *nfsd4_client_from_rqst(struct svc_rqst *rqst); #else static inline int nfsd4_init_slabs(void) { return 0; } static inline void nfsd4_free_slabs(void) { } @@ -139,6 +140,7 @@ static inline bool nfsd4_spo_must_allow(struct svc_rqst *rqstp) { return false; } +void *nfsd4_client_from_rqst(struct svc_rqst *rqst) { return NULL; } #endif /* diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index fe62bc744143..fc9b9ad1d444 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -395,8 +395,8 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap, bool get_write_count; bool size_change = (iap->ia_valid & ATTR_SIZE); struct deleg_break_ctl deleg_break_ctl = { - .delegated_inode = DELEG_NO_WAIT, - .who = rqstp + .delegated_inode = DELEG_NO_WAIT, + .who = nfsd4_client_from_rqst(rqstp), }; if (iap->ia_valid & (ATTR_ATIME | ATTR_MTIME | ATTR_SIZE)) @@ -1559,7 +1559,7 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp, int host_err; struct deleg_break_ctl deleg_break_ctl = { .delegated_inode = DELEG_NO_WAIT, - .who = rqstp + .who = nfsd4_client_from_rqst(rqstp), }; err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_CREATE); @@ -1636,7 +1636,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen, int host_err; struct deleg_break_ctl deleg_break_ctl = { .delegated_inode = DELEG_NO_WAIT, - .who = rqstp + .who = nfsd4_client_from_rqst(rqstp), }; err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_REMOVE); @@ -1736,7 +1736,7 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int host_err; struct deleg_break_ctl deleg_break_ctl = { .delegated_inode = DELEG_NO_WAIT, - .who = rqstp + .who = nfsd4_client_from_rqst(rqstp), }; err = nfserr_acces;