Short write in nfsd becomes a full write to the client

commit 31dec2538e45e9fff2007ea1f4c6bae9f78db724 upstream.

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>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 4d617ea28cfc0b699868275db4cd95202e23f989..988530d15a8b6bdc324af9ae5e8ef0e8fb7ec68e 100644 (file)
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -201,6 +201,7 @@ 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),
@@ -213,9 +214,9 @@ 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);
 }
 

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index e5b51ffafc6c2c2300fb61f3fb0c0036e0762115..fddc656c081aa96e2d5580faa2a265198d5bf5d0 100644 (file)
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -685,6 +685,7 @@ 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() */
 
@@ -703,7 +704,7 @@ 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;
@@ -711,10 +712,12 @@ 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;

diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index 0766f95d236a23cf73f247bea43e4d0b28c61844..20c63b27f20b1a4514d7635dc7eb71190d7e3b40 100644 (file)
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -179,6 +179,7 @@ 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),
@@ -187,7 +188,7 @@ 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);
 }

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 18060bed5267451c005345ef19f5a270ee5143aa..8b38bcf7a49bc0d042f00fb6f9fd6ef58076c951 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -957,7 +957,7 @@ 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;
@@ -971,7 +971,7 @@ 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
 
@@ -1003,7 +1003,7 @@ 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);
        }
 
@@ -1048,9 +1048,10 @@ 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;
@@ -1092,7 +1093,7 @@ 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;

diff --git a/include/linux/nfsd/nfsd.h b/include/linux/nfsd/nfsd.h
index 108f47e5fd9511796516d758dca90b1232321bea..9af9bcaedcd3ee29785372da4e1a825079e0b1a6 100644 (file)
--- a/include/linux/nfsd/nfsd.h
+++ b/include/linux/nfsd/nfsd.h
@@ -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 *,