On Tue, Nov 04, 2014 at 03:38:28PM -0500, Trond Myklebust wrote:
> Hi Ben,
>
> On Tue, Nov 4, 2014 at 10:47 AM, Benjamin Coddington
> <bcodding@xxxxxxxxxx> wrote:
> > I have a customer that would like the client to use DATA_SYNC instead of
> > FILE_SYNC when writing a file with O_DSYNC. It looks like the client will
> > only use FILE_SYNC since:
> >
> > 87ed5eb44ad9338b1617 NFS: Don't use DATA_SYNC writes
> > http://marc.info/?l=git-commits-head&m=131180398113265&w=2
> >
> > I've been unable to dig up any other discussion on this, so I think it
> > has just been an overlooked point until now. I'm only starting to
> > figure out what would need to change for this, and I thought that while
> > I do that I'd ask the list if anyone thinks that serious implementation
> > issues might emerge if this were attempted.
>
> I'm not aware of any servers that make a real distinction between
> FILE_SYNC and DATA_SYNC. Has anybody done any performance measurements
> to show that it is worth the effort?
For a fully allocated file the difference between fdatasync and fsync
or O_DSYNC / O_SYNC can make a difference, this is especially notiable
on data base workloads that do lots of small I/O on fully preallocated
files.
Implementing this difference for the Linux NFS server also seem fairly
trivial, patch attached.
>From 61fee1aacf2f31b6fb1bb90d90f5e625994970f6 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@xxxxxx>
Date: Wed, 5 Nov 2014 09:50:35 +0100
Subject: nfsd: implement DATA_SYNC4 support
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/nfsd/nfs3proc.c | 4 ++--
fs/nfsd/nfs4proc.c | 7 +++----
fs/nfsd/nfsproc.c | 7 ++-----
fs/nfsd/vfs.c | 14 +++++++-------
fs/nfsd/vfs.h | 3 ++-
5 files changed, 16 insertions(+), 19 deletions(-)
diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 12f2aab..cc9622f 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -191,12 +191,12 @@ nfsd3_proc_write(struct svc_rqst *rqstp, struct nfsd3_writeargs *argp,
argp->stable? " stable" : "");
fh_copy(&resp->fh, &argp->fh);
- resp->committed = argp->stable;
nfserr = nfsd_write(rqstp, &resp->fh, NULL,
argp->offset,
rqstp->rq_vec, argp->vlen,
&cnt,
- &resp->committed);
+ argp->stable);
+ resp->committed = argp->stable;
resp->count = cnt;
RETURN_STATUS(nfserr);
}
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index c4a2adc..b11fd3b 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -998,15 +998,14 @@ nfsd4_write(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
}
cnt = write->wr_buflen;
- write->wr_how_written = write->wr_stable_how;
gen_boot_verifier(&write->wr_verifier, SVC_NET(rqstp));
nvecs = fill_in_write_vector(rqstp->rq_vec, write);
WARN_ON_ONCE(nvecs > ARRAY_SIZE(rqstp->rq_vec));
- status = nfsd_write(rqstp, &cstate->current_fh, filp,
- write->wr_offset, rqstp->rq_vec, nvecs,
- &cnt, &write->wr_how_written);
+ status = nfsd_write(rqstp, &cstate->current_fh, filp, write->wr_offset,
+ rqstp->rq_vec, nvecs, &cnt, write->wr_stable_how);
+ write->wr_how_written = write->wr_stable_how;
if (filp)
fput(filp);
diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index b868073..90caa00 100644
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -158,7 +158,6 @@ nfsd_proc_write(struct svc_rqst *rqstp, struct nfsd_writeargs *argp,
struct nfsd_attrstat *resp)
{
__be32 nfserr;
- int stable = 1;
unsigned long cnt = argp->len;
dprintk("nfsd: WRITE %s %d bytes at %d\n",
@@ -166,10 +165,8 @@ nfsd_proc_write(struct svc_rqst *rqstp, struct nfsd_writeargs *argp,
argp->len, argp->offset);
nfserr = nfsd_write(rqstp, fh_copy(&resp->fh, &argp->fh), NULL,
- argp->offset,
- rqstp->rq_vec, argp->vlen,
- &cnt,
- &stable);
+ argp->offset, rqstp->rq_vec, argp->vlen,
+ &cnt, NFS_FILE_SYNC);
return nfsd_return_attrs(nfserr, resp);
}
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 989129e..2ea8ff6 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -927,7 +927,7 @@ static int wait_for_concurrent_writes(struct file *file)
static __be32
nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
loff_t offset, struct kvec *vec, int vlen,
- unsigned long *cnt, int *stablep)
+ unsigned long *cnt, enum nfs3_stable_how stable)
{
struct svc_export *exp;
struct dentry *dentry;
@@ -935,7 +935,6 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
mm_segment_t oldfs;
__be32 err = 0;
int host_err;
- int stable = *stablep;
int use_wgather;
loff_t pos = offset;
unsigned int pflags = current->flags;
@@ -956,7 +955,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
use_wgather = (rqstp->rq_vers == 2) && EX_WGATHER(exp);
if (!EX_ISSYNC(exp))
- stable = 0;
+ stable = NFS_UNSTABLE;
/* Write the data. */
oldfs = get_fs(); set_fs(KERNEL_DS);
@@ -972,7 +971,8 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
if (use_wgather)
host_err = wait_for_concurrent_writes(file);
else
- host_err = vfs_fsync_range(file, offset, offset+*cnt, 0);
+ host_err = vfs_fsync_range(file, offset, offset+*cnt,
+ stable == NFS_DATA_SYNC);
}
out_nfserr:
@@ -1051,7 +1051,7 @@ __be32 nfsd_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
__be32
nfsd_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
loff_t offset, struct kvec *vec, int vlen, unsigned long *cnt,
- int *stablep)
+ enum nfs3_stable_how stable)
{
__be32 err = 0;
@@ -1061,7 +1061,7 @@ nfsd_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
if (err)
goto out;
err = nfsd_vfs_write(rqstp, fhp, file, offset, vec, vlen, cnt,
- stablep);
+ stable);
} else {
err = nfsd_open(rqstp, fhp, S_IFREG, NFSD_MAY_WRITE, &file);
if (err)
@@ -1069,7 +1069,7 @@ nfsd_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
if (cnt)
err = nfsd_vfs_write(rqstp, fhp, file, offset, vec, vlen,
- cnt, stablep);
+ cnt, stable);
nfsd_close(file);
}
out:
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index c2ff3f1..3cb8e55 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -81,7 +81,8 @@ __be32 nfsd_readv(struct file *, loff_t, struct kvec *, int,
__be32 nfsd_read(struct svc_rqst *, struct svc_fh *,
loff_t, struct kvec *, int, unsigned long *);
__be32 nfsd_write(struct svc_rqst *, struct svc_fh *,struct file *,
- loff_t, struct kvec *,int, unsigned long *, int *);
+ loff_t, struct kvec *,int, unsigned long *,
+ enum nfs3_stable_how);
__be32 nfsd_readlink(struct svc_rqst *, struct svc_fh *,
char *, int *);
__be32 nfsd_symlink(struct svc_rqst *, struct svc_fh *,
--
1.9.1
