[PATCH] knfsd: nfs4: hold filp while reading or writing

We're trying to read and write from a struct file that we may not hold a
reference to any more (since a close could be processed as soon as we drop the
state lock).

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/nfsd/nfs4proc.c

@@ -45,6 +45,7 @@
 #include <linux/param.h>
 #include <linux/major.h>
 #include <linux/slab.h>
+#include <linux/file.h>
 
 #include <linux/sunrpc/svc.h>
 #include <linux/nfsd/nfsd.h>
@@ -477,26 +478,27 @@ static inline int
 nfsd4_read(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_read *read)
 {
 	int status;
-	struct file *filp = NULL;
 
 	/* no need to check permission - this will be done in nfsd_read() */
 
+	read->rd_filp = NULL;
 	if (read->rd_offset >= OFFSET_MAX)
 		return nfserr_inval;
 
 	nfs4_lock_state();
 	/* check stateid */
 	if ((status = nfs4_preprocess_stateid_op(current_fh, &read->rd_stateid,
-					CHECK_FH | RD_STATE, &filp))) {
+				CHECK_FH | RD_STATE, &read->rd_filp))) {
 		dprintk("NFSD: nfsd4_read: couldn't process stateid!\n");
 		goto out;
 	}
+	if (read->rd_filp)
+		get_file(read->rd_filp);
 	status = nfs_ok;
 out:
 	nfs4_unlock_state();
 	read->rd_rqstp = rqstp;
 	read->rd_fhp = current_fh;
-	read->rd_filp = filp;
 	return status;
 }
 
@@ -633,6 +635,8 @@ nfsd4_write(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_writ
 		dprintk("NFSD: nfsd4_write: couldn't process stateid!\n");
 		goto out;
 	}
+	if (filp)
+		get_file(filp);
 	nfs4_unlock_state();
 
 	write->wr_bytes_written = write->wr_buflen;
@@ -644,6 +648,8 @@ nfsd4_write(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_writ
 	status =  nfsd_write(rqstp, current_fh, filp, write->wr_offset,
 			write->wr_vec, write->wr_vlen, write->wr_buflen,
 			&write->wr_how_written);
+	if (filp)
+		fput(filp);
 
 	if (status == nfserr_symlink)
 		status = nfserr_inval;
@@ -932,6 +938,9 @@ encode_op:
 			nfs4_put_stateowner(replay_owner);
 			replay_owner = NULL;
 		}
+		/* XXX Ugh, we need to get rid of this kind of special case: */
+		if (op->opnum == OP_READ && op->u.read.rd_filp)
+			fput(op->u.read.rd_filp);
 	}
 
 out: