nfsd: vfs_llseek() with 32 or 64 bit offsets (hashes)

Use 32-bit or 64-bit llseek() hashes for directory offsets depending on
the NFS version. NFSv2 gets 32-bit hashes only.

NOTE: This patch got rather complex as Christoph asked to set the
filp->f_mode flag in the open call or immediatly after dentry_open()
in nfsd_open() to avoid races.
Personally I still do not see a reason for that and in my opinion
FMODE_32BITHASH/FMODE_64BITHASH flags could be set nfsd_readdir(), as it
follows directly after nfsd_open() without a chance of races.

Signed-off-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Acked-by: J. Bruce Fields<bfields@redhat.com>

2 files changed, 15 insertions, 2 deletions

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index a6db4cb874d5..7423d712eb8c 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -796,9 +796,15 @@ nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
                             flags, current_cred());
         if (IS_ERR(*filp))
                 host_err = PTR_ERR(*filp);
-        else
+        else {
                 host_err = ima_file_check(*filp, may_flags);
 
+                if (may_flags & NFSD_MAY_64BIT_COOKIE)
+                        (*filp)->f_mode |= FMODE_64BITHASH;
+                else
+                        (*filp)->f_mode |= FMODE_32BITHASH;
+        }
+
 out_nfserr:
         err = nfserrno(host_err);
 out:
@@ -2022,8 +2028,13 @@ nfsd_readdir(struct svc_rqst *rqstp, struct svc_fh *fhp, loff_t *offsetp,
         __be32          err;
         struct file     *file;
         loff_t          offset = *offsetp;
+        int             may_flags = NFSD_MAY_READ;
+
+        /* NFSv2 only supports 32 bit cookies */
+        if (rqstp->rq_vers > 2)
+                may_flags |= NFSD_MAY_64BIT_COOKIE;
 
-        err = nfsd_open(rqstp, fhp, S_IFDIR, NFSD_MAY_READ, &file);
+        err = nfsd_open(rqstp, fhp, S_IFDIR, may_flags, &file);
         if (err)
                 goto out;
 
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index 1dcd238e11a0..ec0611b2b738 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -27,6 +27,8 @@
 #define NFSD_MAY_BYPASS_GSS             0x400
 #define NFSD_MAY_READ_IF_EXEC           0x800
 
+#define NFSD_MAY_64BIT_COOKIE           0x1000 /* 64 bit readdir cookies for >= NFSv3 */
+
 #define NFSD_MAY_CREATE         (NFSD_MAY_EXEC|NFSD_MAY_WRITE)
 #define NFSD_MAY_REMOVE         (NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC)