Commit 31dec253 authored by David Shaw's avatar David Shaw Committed by J. Bruce Fields
Browse files

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: default avatarDavid Shaw <dshaw@jabberwocky.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
parent 1e685ec2

fs/nfsd/nfs3proc.c

+3 −2
Original line number Diff line number Diff line
@@ -203,6 +203,7 @@ nfsd3_proc_write(struct svc_rqst *rqstp, struct nfsd3_writeargs *argp, 
					 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 @@ nfsd3_proc_write(struct svc_rqst *rqstp, struct nfsd3_writeargs *argp, 
	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);

}

fs/nfsd/nfs4proc.c

+5 −2
Original line number Diff line number Diff line
@@ -682,6 +682,7 @@ nfsd4_write(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, 
	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 @@ nfsd4_write(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, 
		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 @@ nfsd4_write(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, 


	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;

fs/nfsd/nfsproc.c

+2 −1
Original line number Diff line number Diff line
@@ -180,6 +180,7 @@ nfsd_proc_write(struct svc_rqst *rqstp, struct nfsd_writeargs *argp, 
{

	__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 @@ nfsd_proc_write(struct svc_rqst *rqstp, struct nfsd_writeargs *argp, 
	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);

}

fs/nfsd/vfs.c

+7 −6
Original line number Diff line number Diff line
@@ -960,7 +960,7 @@ static void kill_suid(struct dentry *dentry) 
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 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file, 
	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 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file, 
	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 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file, 
	}



	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 @@ out: 
 */

__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;

include/linux/nfsd/nfsd.h

+1 −1
Original line number Diff line number Diff line
@@ -105,7 +105,7 @@ void nfsd_close(struct file *); 
__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 *,

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