There are cases with NFSv3 where the client doesn't actually care about
WCC attributes in replies. If the server is mainly acting as a DS for
flexfiles, then the client just throws out those attributes anyway.
Also, in the case where the client is primarily doing direct I/O, post
op attributes aren't terribly useful
Another reason to allow turning these off is that NFS will flush all
buffered writes prior to issuing a GETATTR, and it also takes the
i_mutex in its ->getattr operation.
If we're doing a vfs_getattr after most RPCs, then we can end up
deadlocking or (at best) prematurely flushing buffered writes, which
kills performance.
This patch adds a new export option -- "nowcc" that disables the return
of WCC attributes in NFSv3 replies. I also have a userland patch that
adds support for the same option to nfs-utils that I'll send along as
well.
Signed-off-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
---
fs/nfsd/export.c | 1 +
fs/nfsd/nfs3xdr.c | 5 ++++-
fs/nfsd/nfsfh.c | 4 ++++
fs/nfsd/nfsfh.h | 5 ++++-
include/uapi/linux/nfsd/export.h | 3 ++-
5 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index b4d84b579f20..97258009ce1e 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -1092,6 +1092,7 @@ static struct flags {
{ NFSEXP_NOAUTHNLM, {"insecure_locks", ""}},
{ NFSEXP_V4ROOT, {"v4root", ""}},
{ NFSEXP_PNFS, {"pnfs", ""}},
+ { NFSEXP_NOWCC, {"nowcc", ""}},
{ 0, {"", ""}}
};
diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 01dcd494f781..c30c8c604e2a 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -203,7 +203,7 @@ static __be32 *
encode_post_op_attr(struct svc_rqst *rqstp, __be32 *p, struct svc_fh *fhp)
{
struct dentry *dentry = fhp->fh_dentry;
- if (dentry && d_really_is_positive(dentry)) {
+ if (!fhp->fh_no_wcc && dentry && d_really_is_positive(dentry)) {
__be32 err;
struct kstat stat;
@@ -256,6 +256,9 @@ void fill_post_wcc(struct svc_fh *fhp)
{
__be32 err;
+ if (fhp->fh_no_wcc)
+ return;
+
if (fhp->fh_post_saved)
printk("nfsd: inode locked twice during operation.\n");
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 350041a40fe5..32093b7dce55 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -267,6 +267,9 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
fhp->fh_dentry = dentry;
fhp->fh_export = exp;
+ if (exp->ex_flags & NFSEXP_NOWCC && rqstp->rq_vers == 3)
+ fhp->fh_no_wcc = true;
+
return 0;
out:
exp_put(exp);
@@ -641,6 +644,7 @@ fh_put(struct svc_fh *fhp)
exp_put(exp);
fhp->fh_export = NULL;
}
+ fhp->fh_no_wcc = false;
return;
}
diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
index 1e90dad4926b..9ddead4d98f8 100644
--- a/fs/nfsd/nfsfh.h
+++ b/fs/nfsd/nfsfh.h
@@ -32,6 +32,7 @@ typedef struct svc_fh {
unsigned char fh_locked; /* inode locked by us */
unsigned char fh_want_write; /* remount protection taken */
+ bool fh_no_wcc; /* no wcc data needed */
#ifdef CONFIG_NFSD_V3
unsigned char fh_post_saved; /* post-op attrs saved */
@@ -51,7 +52,6 @@ typedef struct svc_fh {
struct kstat fh_post_attr; /* full attrs after operation */
u64 fh_post_change; /* nfsv4 change; see above */
#endif /* CONFIG_NFSD_V3 */
-
} svc_fh;
enum nfsd_fsid {
@@ -225,6 +225,9 @@ fill_pre_wcc(struct svc_fh *fhp)
{
struct inode *inode;
+ if (fhp->fh_no_wcc)
+ return;
+
inode = d_inode(fhp->fh_dentry);
if (!fhp->fh_pre_saved) {
fhp->fh_pre_mtime = inode->i_mtime;
diff --git a/include/uapi/linux/nfsd/export.h b/include/uapi/linux/nfsd/export.h
index 0df7bd5d2fb1..4c132290f414 100644
--- a/include/uapi/linux/nfsd/export.h
+++ b/include/uapi/linux/nfsd/export.h
@@ -51,9 +51,10 @@
*/
#define NFSEXP_V4ROOT 0x10000
#define NFSEXP_PNFS 0x20000
+#define NFSEXP_NOWCC 0x40000
/* All flags that we claim to support. (Note we don't support NOACL.) */
-#define NFSEXP_ALLFLAGS 0x3FE7F
+#define NFSEXP_ALLFLAGS 0x7FE7F
/* The flags that may vary depending on security flavor: */
#define NFSEXP_SECINFO_FLAGS (NFSEXP_READONLY | NFSEXP_ROOTSQUASH \
--
2.4.3
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