5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: J. Bruce Fields bfields@redhat.com
[ Upstream commit aba2072f452346d56a462718bcde93d697383148 ]
It's OK to grant a read delegation to a client that holds a write, as long as it's the only client holding the write.
We originally tried to do this in commit 94415b06eb8a ("nfsd4: a client's own opens needn't prevent delegations"), which had to be reverted in commit 6ee65a773096 ("Revert "nfsd4: a client's own opens needn't prevent delegations"").
Signed-off-by: J. Bruce Fields bfields@redhat.com Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/locks.c | 3 ++ fs/nfsd/nfs4state.c | 82 +++++++++++++++++++++++++++++++++++++-------- 2 files changed, 71 insertions(+), 14 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c index 873f97504bddf..101867933e4d3 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -1808,6 +1808,9 @@ check_conflicting_open(struct file *filp, const long arg, int flags)
if (flags & FL_LAYOUT) return 0; + if (flags & FL_DELEG) + /* We leave these checks to the caller */ + return 0;
if (arg == F_RDLCK) return inode_is_open_for_write(inode) ? -EAGAIN : 0; diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 9c8dacf0f2b86..fd0d6e81a2272 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -5030,6 +5030,65 @@ static struct file_lock *nfs4_alloc_init_lease(struct nfs4_delegation *dp, return fl; }
+static int nfsd4_check_conflicting_opens(struct nfs4_client *clp, + struct nfs4_file *fp) +{ + struct nfs4_ol_stateid *st; + struct file *f = fp->fi_deleg_file->nf_file; + struct inode *ino = locks_inode(f); + int writes; + + writes = atomic_read(&ino->i_writecount); + if (!writes) + return 0; + /* + * There could be multiple filehandles (hence multiple + * nfs4_files) referencing this file, but that's not too + * common; let's just give up in that case rather than + * trying to go look up all the clients using that other + * nfs4_file as well: + */ + if (fp->fi_aliased) + return -EAGAIN; + /* + * If there's a close in progress, make sure that we see it + * clear any fi_fds[] entries before we see it decrement + * i_writecount: + */ + smp_mb__after_atomic(); + + if (fp->fi_fds[O_WRONLY]) + writes--; + if (fp->fi_fds[O_RDWR]) + writes--; + if (writes > 0) + return -EAGAIN; /* There may be non-NFSv4 writers */ + /* + * It's possible there are non-NFSv4 write opens in progress, + * but if they haven't incremented i_writecount yet then they + * also haven't called break lease yet; so, they'll break this + * lease soon enough. So, all that's left to check for is NFSv4 + * opens: + */ + spin_lock(&fp->fi_lock); + list_for_each_entry(st, &fp->fi_stateids, st_perfile) { + if (st->st_openstp == NULL /* it's an open */ && + access_permit_write(st) && + st->st_stid.sc_client != clp) { + spin_unlock(&fp->fi_lock); + return -EAGAIN; + } + } + spin_unlock(&fp->fi_lock); + /* + * There's a small chance that we could be racing with another + * NFSv4 open. However, any open that hasn't added itself to + * the fi_stateids list also hasn't called break_lease yet; so, + * they'll break this lease soon enough. + */ + return 0; +} + static struct nfs4_delegation * nfs4_set_delegation(struct nfs4_client *clp, struct svc_fh *fh, struct nfs4_file *fp, struct nfs4_clnt_odstate *odstate) @@ -5049,9 +5108,12 @@ nfs4_set_delegation(struct nfs4_client *clp, struct svc_fh *fh,
nf = find_readable_file(fp); if (!nf) { - /* We should always have a readable file here */ - WARN_ON_ONCE(1); - return ERR_PTR(-EBADF); + /* + * We probably could attempt another open and get a read + * delegation, but for now, don't bother until the + * client actually sends us one. + */ + return ERR_PTR(-EAGAIN); } spin_lock(&state_lock); spin_lock(&fp->fi_lock); @@ -5086,6 +5148,9 @@ nfs4_set_delegation(struct nfs4_client *clp, struct svc_fh *fh, locks_free_lock(fl); if (status) goto out_clnt_odstate; + status = nfsd4_check_conflicting_opens(clp, fp); + if (status) + goto out_unlock;
spin_lock(&state_lock); spin_lock(&fp->fi_lock); @@ -5167,17 +5232,6 @@ nfs4_open_delegation(struct svc_fh *fh, struct nfsd4_open *open, goto out_no_deleg; if (!cb_up || !(oo->oo_flags & NFS4_OO_CONFIRMED)) goto out_no_deleg; - /* - * Also, if the file was opened for write or - * create, there's a good chance the client's - * about to write to it, resulting in an - * immediate recall (since we don't support - * write delegations): - */ - if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) - goto out_no_deleg; - if (open->op_create == NFS4_OPEN_CREATE) - goto out_no_deleg; break; default: goto out_no_deleg;