The branch main has been updated by rmacklem:
URL:
https://cgit.FreeBSD.org/src/commit/?id=5e5ca4c8fc53d31bf71e182e08c4ccd8290428c7
commit 5e5ca4c8fc53d31bf71e182e08c4ccd8290428c7
Author: Rick Macklem <rmack...@freebsd.org>
AuthorDate: 2021-06-09 15:00:43 +0000
Commit: Rick Macklem <rmack...@freebsd.org>
CommitDate: 2021-06-09 15:00:43 +0000
nfscl: Add a "has acquired a delegation" flag for delegations
A problem was reported via email, where a large (130000+) accumulation
of NFSv4 opens on an NFSv4 mount caused significant lock contention
on the mutex used to protect the client mount's open/lock state.
Although the root cause for the accumulation of opens was not
resolved, it is obvious that the NFSv4 client is not designed to
handle 100000+ opens efficiently.
For a common case where delegations are not being issued by the
NFSv4 server, the code acquires the mutex lock for open/lock state,
finds the delegation list empty and just unlocks the mutex and returns.
This patch adds an NFS mount point flag that is set when a delegation
is issued for the mount. Then the patched code checks for this flag
before acquiring the open/lock mutex, avoiding the need to acquire
the lock for the case where delegations are not being issued by the
NFSv4 server.
This change appears to be performance neutral for a small number
of opens, but should reduce lock contention for a large number of opens
for the common case where server is not issuing delegations.
This commit should not affect the high level semantics of delegation
handling.
MFC after: 2 weeks
---
sys/fs/nfsclient/nfs_clstate.c | 44 +++++++++++++++++++++++++++++++++++++++---
sys/fs/nfsclient/nfsmount.h | 1 +
2 files changed, 42 insertions(+), 3 deletions(-)
diff --git a/sys/fs/nfsclient/nfs_clstate.c b/sys/fs/nfsclient/nfs_clstate.c
index 5e4ac2ae9d4d..0659e77289e9 100644
--- a/sys/fs/nfsclient/nfs_clstate.c
+++ b/sys/fs/nfsclient/nfs_clstate.c
@@ -438,20 +438,32 @@ nfscl_deleg(mount_t mp, struct nfsclclient *clp, u_int8_t
*nfhp,
int fhlen, struct ucred *cred, NFSPROC_T *p, struct nfscldeleg **dpp)
{
struct nfscldeleg *dp = *dpp, *tdp;
+ struct nfsmount *nmp;
+ KASSERT(mp != NULL, ("nfscl_deleg: mp NULL"));
+ nmp = VFSTONFS(mp);
/*
* First, if we have received a Read delegation for a file on a
* read/write file system, just return it, because they aren't
* useful, imho.
*/
- if (mp != NULL && dp != NULL && !NFSMNT_RDONLY(mp) &&
+ if (dp != NULL && !NFSMNT_RDONLY(mp) &&
(dp->nfsdl_flags & NFSCLDL_READ)) {
- (void) nfscl_trydelegreturn(dp, cred, VFSTONFS(mp), p);
+ nfscl_trydelegreturn(dp, cred, nmp, p);
free(dp, M_NFSCLDELEG);
*dpp = NULL;
return (0);
}
+ /*
+ * Since a delegation might be added to the mount,
+ * set NFSMNTP_DELEGISSUED now. If a delegation already
+ * exagain ists, setting this flag is harmless.
+ */
+ NFSLOCKMNT(nmp);
+ nmp->nm_privflag |= NFSMNTP_DELEGISSUED;
+ NFSUNLOCKMNT(nmp);
+
/* Look for the correct deleg, based upon FH */
NFSLOCKCLSTATE();
tdp = nfscl_finddeleg(clp, nfhp, fhlen);
@@ -3356,12 +3368,20 @@ nfscl_delegreturnvp(vnode_t vp, NFSPROC_T *p)
struct nfscldeleg *dp;
struct ucred *cred;
struct nfsnode *np;
+ struct nfsmount *nmp;
+ nmp = VFSTONFS(vp->v_mount);
+ NFSLOCKMNT(nmp);
+ if ((nmp->nm_privflag & NFSMNTP_DELEGISSUED) == 0) {
+ NFSUNLOCKMNT(nmp);
+ return;
+ }
+ NFSUNLOCKMNT(nmp);
np = VTONFS(vp);
cred = newnfs_getcred();
dp = NULL;
NFSLOCKCLSTATE();
- clp = VFSTONFS(vp->v_mount)->nm_clp;
+ clp = nmp->nm_clp;
if (clp != NULL)
dp = nfscl_finddeleg(clp, np->n_fhp->nfh_fh,
np->n_fhp->nfh_len);
@@ -4500,6 +4520,12 @@ nfscl_nodeleg(vnode_t vp, int writedeleg)
nmp = VFSTONFS(vp->v_mount);
if (!NFSHASNFSV4(nmp))
return (1);
+ NFSLOCKMNT(nmp);
+ if ((nmp->nm_privflag & NFSMNTP_DELEGISSUED) == 0) {
+ NFSUNLOCKMNT(nmp);
+ return (1);
+ }
+ NFSUNLOCKMNT(nmp);
NFSLOCKCLSTATE();
clp = nfscl_findcl(nmp);
if (clp == NULL) {
@@ -4856,6 +4882,12 @@ nfscl_delegmodtime(vnode_t vp)
nmp = VFSTONFS(vp->v_mount);
if (!NFSHASNFSV4(nmp))
return;
+ NFSLOCKMNT(nmp);
+ if ((nmp->nm_privflag & NFSMNTP_DELEGISSUED) == 0) {
+ NFSUNLOCKMNT(nmp);
+ return;
+ }
+ NFSUNLOCKMNT(nmp);
NFSLOCKCLSTATE();
clp = nfscl_findcl(nmp);
if (clp == NULL) {
@@ -4885,6 +4917,12 @@ nfscl_deleggetmodtime(vnode_t vp, struct timespec *mtime)
nmp = VFSTONFS(vp->v_mount);
if (!NFSHASNFSV4(nmp))
return;
+ NFSLOCKMNT(nmp);
+ if ((nmp->nm_privflag & NFSMNTP_DELEGISSUED) == 0) {
+ NFSUNLOCKMNT(nmp);
+ return;
+ }
+ NFSUNLOCKMNT(nmp);
NFSLOCKCLSTATE();
clp = nfscl_findcl(nmp);
if (clp == NULL) {
diff --git a/sys/fs/nfsclient/nfsmount.h b/sys/fs/nfsclient/nfsmount.h
index 57adcd8f2fca..f8ea8c9a1418 100644
--- a/sys/fs/nfsclient/nfsmount.h
+++ b/sys/fs/nfsclient/nfsmount.h
@@ -115,6 +115,7 @@ struct nfsmount {
#define NFSMNTP_NOXATTR 0x00000080
#define NFSMNTP_NOADVISE 0x00000100
#define NFSMNTP_NOALLOCATE 0x00000200
+#define NFSMNTP_DELEGISSUED 0x00000400
/* New mount flags only used by the kernel via nmount(2). */
#define NFSMNT_TLS 0x00000001
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