NFSD: restrict PF_LESS_THROTTLE to loop-back requests.
Subsystems (3)
cover NFSD: restrict PF_LESS_THROTTLE to loop-back requests.
As PF_LESS_THROTTLE now has a slightly broader meaning it makes sense to restrict it to only the times it is actually needed - when write requests come from the local host.
Thanks,
NeilBrown
---
NeilBrown (2):
SUNRPC: track whether a request is coming from a loop-back interface.
nfsd: Only set PF_LESS_THROTTLE when really needed.
fs/nfsd/nfssvc.c | 6 ------ fs/nfsd/vfs.c | 12 ++++++++++++ include/linux/sunrpc/svc.h | 1 + include/linux/sunrpc/svc_xprt.h | 1 + net/sunrpc/sunrpc.h | 13 +++++++++++++ net/sunrpc/svcsock.c | 5 +++++ 6 files changed, 32 insertions(+), 6 deletions(-)
Signature · 1 line
Signature
PATCH 1/2 SUNRPC: track whether a request is coming from a loop-back interface.
If an incoming NFS request is coming from the local host, then nfsd will need to perform some special handling. So detect that possibility and make the source visible in rq_local.
--- include/linux/sunrpc/svc.h | 1 + include/linux/sunrpc/svc_xprt.h | 1 + net/sunrpc/sunrpc.h | 13 +++++++++++++ net/sunrpc/svcsock.c | 5 +++++ 4 files changed, 20 insertions(+)
include/linux/sunrpc/svc.h +1 -0
@@ -254,6 +254,7 @@ struct svc_rqst {u32 rq_prot;/* IP protocol */ unsigned short rq_secure : 1; /* secure port */ + unsigned short rq_local : 1; /* local request */void * rq_argp;/* decoded arguments */ void * rq_resp;/* xdr'd results */
include/linux/sunrpc/svc_xprt.h +1 -0
@@ -63,6 +63,7 @@ struct svc_xprt {#define XPT_DETACHED 10/* detached from tempsocks list */ #define XPT_LISTENER 11/* listening endpoint */ #define XPT_CACHE_AUTH 12/* cache auth info */ +#define XPT_LOCAL 13/* connection from loopback interface */ struct svc_serv *xpt_server;/* service for transport */ atomic_t xpt_reserved;/* space on outq that is rsvd */
net/sunrpc/sunrpc.h +13 -0
@@ -43,6 +43,19 @@ static inline int rpc_reply_expected(struct rpc_task *task) (task->tk_msg.rpc_proc->p_decode !=NULL ); } +static inline int sock_is_loopback (struct sock *sk) +{ +struct dst_entry *dst; +int loopback =0 ; +rcu_read_lock (); + dst =rcu_dereference (sk->sk_dst_cache); +if (dst && dst->dev && + (dst->dev->features &NETIF_F_LOOPBACK )) + loopback =1 ; +rcu_read_unlock (); +return loopback; +} +int svc_send_common (struct socket *sock,struct xdr_buf *xdr,struct page *headpage,unsigned long headoffset,struct page *tailpage,unsigned long tailoffset);
net/sunrpc/svcsock.c +5 -0
@@ -867,6 +867,10 @@ static struct svc_xprt *svc_tcp_accept(struct svc_xprt *xprt) }svc_xprt_set_local (&newsvsk->sk_xprt, sin, slen); +if (sock_is_loopback (newsock->sk)) +set_bit (XPT_LOCAL , &newsvsk->sk_xprt.xpt_flags); +else +clear_bit (XPT_LOCAL , &newsvsk->sk_xprt.xpt_flags);if (serv->sv_stats) serv->sv_stats->nettcpconn++;
@@ -1112,6 +1116,7 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp) rqstp->rq_xprt_ctxt =NULL ; rqstp->rq_prot =IPPROTO_TCP ; + rqstp->rq_local = !!test_bit (XPT_LOCAL , &svsk->sk_xprt.xpt_flags); p = (__be32 *)rqstp->rq_arg.head[0 ].iov_base; calldir = p[1 ];
PATCH 2/2 nfsd: Only set PF_LESS_THROTTLE when really needed.
In reply to NeilBrownPF_LESS_THROTTLE has a very specific use case: to avoid deadlocks and live-locks while writing to the page cache in a loop-back NFS mount situation.
It therefore makes sense to *only* set PF_LESS_THROTTLE in this situation.
We now know when a request came from the local-host so it could be a loop-back mount. We already know when we are handling write requests, and when we are doing anything else.
So combine those two to allow nfsd to still be throttled (like any other process) in every situation except when it is known to be problematic.
--- fs/nfsd/nfssvc.c | 6 ------ fs/nfsd/vfs.c | 12 ++++++++++++ 2 files changed, 12 insertions(+), 6 deletions(-)
fs/nfsd/nfssvc.c +0 -6
@@ -591,12 +591,6 @@ nfsd(void *vrqstp) nfsdstats.th_cnt++;mutex_unlock (&nfsd_mutex); -/* -* We want less throttling in balance_dirty_pages() so that nfs to -* localhost doesn't cause nfsd to lock up due to all the client's -* dirty pages. -*/ - current->flags |=PF_LESS_THROTTLE ;set_freezable ();/*
fs/nfsd/vfs.c +12 -0
@@ -922,6 +922,16 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,int stable = *stablep;int use_wgather;loff_t pos = offset; +unsigned int pflags = current->flags; + +if (rqstp->rq_local) +/* +* We want less throttling in balance_dirty_pages() +* and shrink_inactive_list() so that nfs to +* localhost doesn't cause nfsd to lock up due to all +* the client's dirty pages or its congested queue. +*/ + current->flags |=PF_LESS_THROTTLE ; dentry = file->f_path.dentry; inode = dentry->d_inode;
@@ -959,6 +969,8 @@ out_nfserr: err =0 ; else err =nfserrno (host_err); +if (rqstp->rq_local) +tsk_restore_flags (current, pflags,PF_LESS_THROTTLE );return err; }
Quoted 3 lines · NeilBrown
As
PF_LESS_THROTTLEnow has a slightly broader meaning it makes sense to restrict it to only the times it is actually needed - when write requests come from the local host.
Both look good to me, thanks. Applying for 3.16.
--b.
Quoted 22 lines
Thanks,
NeilBrown---
NeilBrown (2):
SUNRPC: track whether a request is coming from a loop-back interface.
nfsd: Only setPF_LESS_THROTTLEwhen really needed.fs/nfsd/nfssvc.c | 6 ------ fs/nfsd/vfs.c | 12 ++++++++++++ include/linux/sunrpc/svc.h | 1 + include/linux/sunrpc/svc_xprt.h | 1 + net/sunrpc/sunrpc.h | 13 +++++++++++++ net/sunrpc/svcsock.c | 5 +++++ 6 files changed, 32 insertions(+), 6 deletions(-)Signature · 1 line
Signature