Short write in nfsd becomes a full write to the client
If a filesystem being written to via NFS returns a short write count
(as opposed to an error) to nfsd, nfsd treats that as a success for
the entire write, rather than the short count that actually succeeded.
For example, given a 8192 byte write, if the underlying filesystem
only writes 4096 bytes, nfsd will ack back to the nfs client that all
8192 bytes were written. The nfs client does have retry logic for
short writes, but this is never called as the client is told the
complete write succeeded.
There are probably other ways it could happen, but in my case it
happened with a fuse (filesystem in userspace) filesystem which can
rather easily have a partial write.
Here is a patch to properly return the short write count to the
client.
Signed-off-by: David Shaw <dshaw@jabberwocky.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 579ce8c..7c9fe83 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -203,6 +203,7 @@
struct nfsd3_writeres *resp)
{
__be32 nfserr;
+ unsigned long cnt = argp->len;
dprintk("nfsd: WRITE(3) %s %d bytes at %ld%s\n",
SVCFH_fmt(&argp->fh),
@@ -215,9 +216,9 @@
nfserr = nfsd_write(rqstp, &resp->fh, NULL,
argp->offset,
rqstp->rq_vec, argp->vlen,
- argp->len,
+ &cnt,
&resp->committed);
- resp->count = argp->count;
+ resp->count = cnt;
RETURN_STATUS(nfserr);
}
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 77f584f..283d77a 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -682,6 +682,7 @@
struct file *filp = NULL;
u32 *p;
__be32 status = nfs_ok;
+ unsigned long cnt;
/* no need to check permission - this will be done in nfsd_write() */
@@ -700,7 +701,7 @@
return status;
}
- write->wr_bytes_written = write->wr_buflen;
+ cnt = write->wr_buflen;
write->wr_how_written = write->wr_stable_how;
p = (u32 *)write->wr_verifier.data;
*p++ = nfssvc_boot.tv_sec;
@@ -708,10 +709,12 @@
status = nfsd_write(rqstp, &cstate->current_fh, filp,
write->wr_offset, rqstp->rq_vec, write->wr_vlen,
- write->wr_buflen, &write->wr_how_written);
+ &cnt, &write->wr_how_written);
if (filp)
fput(filp);
+ write->wr_bytes_written = cnt;
+
if (status == nfserr_symlink)
status = nfserr_inval;
return status;
diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index 6f7f263..e298e26 100644
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -180,6 +180,7 @@
{
__be32 nfserr;
int stable = 1;
+ unsigned long cnt = argp->len;
dprintk("nfsd: WRITE %s %d bytes at %d\n",
SVCFH_fmt(&argp->fh),
@@ -188,7 +189,7 @@
nfserr = nfsd_write(rqstp, fh_copy(&resp->fh, &argp->fh), NULL,
argp->offset,
rqstp->rq_vec, argp->vlen,
- argp->len,
+ &cnt,
&stable);
return nfsd_return_attrs(nfserr, resp);
}
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 0c07629..54404d7 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -960,7 +960,7 @@
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, int *stablep)
{
struct svc_export *exp;
struct dentry *dentry;
@@ -974,7 +974,7 @@
err = nfserr_perm;
if ((fhp->fh_export->ex_flags & NFSEXP_MSNFS) &&
- (!lock_may_write(file->f_path.dentry->d_inode, offset, cnt)))
+ (!lock_may_write(file->f_path.dentry->d_inode, offset, *cnt)))
goto out;
#endif
@@ -1006,7 +1006,7 @@
host_err = vfs_writev(file, (struct iovec __user *)vec, vlen, &offset);
set_fs(oldfs);
if (host_err >= 0) {
- nfsdstats.io_write += cnt;
+ nfsdstats.io_write += host_err;
fsnotify_modify(file->f_path.dentry);
}
@@ -1051,9 +1051,10 @@
}
dprintk("nfsd: write complete host_err=%d\n", host_err);
- if (host_err >= 0)
+ if (host_err >= 0) {
err = 0;
- else
+ *cnt = host_err;
+ } else
err = nfserrno(host_err);
out:
return err;
@@ -1095,7 +1096,7 @@
*/
__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,
+ loff_t offset, struct kvec *vec, int vlen, unsigned long *cnt,
int *stablep)
{
__be32 err = 0;
diff --git a/include/linux/nfsd/nfsd.h b/include/linux/nfsd/nfsd.h
index 16f7b40..54beda1 100644
--- a/include/linux/nfsd/nfsd.h
+++ b/include/linux/nfsd/nfsd.h
@@ -105,7 +105,7 @@
__be32 nfsd_read(struct svc_rqst *, struct svc_fh *, struct file *,
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 *, int *);
__be32 nfsd_readlink(struct svc_rqst *, struct svc_fh *,
char *, int *);
__be32 nfsd_symlink(struct svc_rqst *, struct svc_fh *,