Commit cf5b4059 authored by Trond Myklebust's avatar Trond Myklebust Committed by Anna Schumaker
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NFSv4: Fix races between open and dentry revalidation 



We want to make sure that we revalidate the dentry if and only if
we've done an OPEN by filename.
In order to avoid races with remote changes to the directory on the
server, we want to save the verifier before calling OPEN. The exception
is if the server returned a delegation with our OPEN, as we then
know that the filename can't have changed on the server.

Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
Reviewed-by: default avatarBenjamin Coddington <bcodding@gmail.com>
Tested-by: default avatarBenjamin Coddington <bcodding@gmail.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent a1147b82

fs/nfs/nfs4file.c

+0 −1
Original line number Diff line number Diff line
@@ -87,7 +87,6 @@ nfs4_file_open(struct inode *inode, struct file *filp) 
	if (inode != d_inode(dentry))

		goto out_drop;



	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));

	nfs_file_set_open_context(filp, ctx);

	nfs_fscache_open_file(inode, filp);

	err = 0;

fs/nfs/nfs4proc.c

+16 −2
Original line number Diff line number Diff line
@@ -2974,10 +2974,13 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata, 
	struct dentry *dentry;

	struct nfs4_state *state;

	fmode_t acc_mode = _nfs4_ctx_to_accessmode(ctx);

	struct inode *dir = d_inode(opendata->dir);

	unsigned long dir_verifier;

	unsigned int seq;

	int ret;



	seq = raw_seqcount_begin(&sp->so_reclaim_seqcount);

	dir_verifier = nfs_save_change_attribute(dir);



	ret = _nfs4_proc_open(opendata, ctx);

	if (ret != 0)
@@ -3005,8 +3008,19 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata, 
			dput(ctx->dentry);

			ctx->dentry = dentry = alias;

		}

		nfs_set_verifier(dentry,

				nfs_save_change_attribute(d_inode(opendata->dir)));

	}



	switch(opendata->o_arg.claim) {

	default:

		break;

	case NFS4_OPEN_CLAIM_NULL:

	case NFS4_OPEN_CLAIM_DELEGATE_CUR:

	case NFS4_OPEN_CLAIM_DELEGATE_PREV:

		if (!opendata->rpc_done)

			break;

		if (opendata->o_res.delegation_type != 0)

			dir_verifier = nfs_save_change_attribute(dir);

		nfs_set_verifier(dentry, dir_verifier);

	}



	/* Parse layoutget results before we check for access */

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