jfs: fix readdir cookie incompatibility with NFSv4

commit 44512449c0ab368889dd13ae0031fba74ee7e1d2 upstream.

NFSv4 reserves readdir cookie values 0-2 for special entries (. and ..),
but jfs allows a value of 2 for a non-special entry. This incompatibility
can result in the nfs client reporting a readdir loop.

This patch doesn't change the value stored internally, but adds one to
the value exposed to the iterate method.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
[bwh: Backported to 3.2:
 - Adjust context
 - s/ctx->pos/filp->f_pos/]
Tested-by: Christian Kujau <lists@nerdbynature.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 23 insertions, 8 deletions

diff --git a/fs/jfs/jfs_dtree.c b/fs/jfs/jfs_dtree.c
index 0ddbeceafc62..c450fdb3d78d 100644
--- a/fs/jfs/jfs_dtree.c
+++ b/fs/jfs/jfs_dtree.c
@@ -3047,6 +3047,14 @@ int jfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 
                 dir_index = (u32) filp->f_pos;
 
+                /*
+                 * NFSv4 reserves cookies 1 and 2 for . and .. so we add
+                 * the value we return to the vfs is one greater than the
+                 * one we use internally.
+                 */
+                if (dir_index)
+                        dir_index--;
+
                 if (dir_index > 1) {
                         struct dir_table_slot dirtab_slot;
 
@@ -3086,7 +3094,7 @@ int jfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
                         if (p->header.flag & BT_INTERNAL) {
                                 jfs_err("jfs_readdir: bad index table");
                                 DT_PUTPAGE(mp);
-                                filp->f_pos = -1;
+                                filp->f_pos = DIREND;
                                 return 0;
                         }
                 } else {
@@ -3094,7 +3102,7 @@ int jfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
                                 /*
                                  * self "."
                                  */
-                                filp->f_pos = 0;
+                                filp->f_pos = 1;
                                 if (filldir(dirent, ".", 1, 0, ip->i_ino,
                                             DT_DIR))
                                         return 0;
@@ -3102,7 +3110,7 @@ int jfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
                         /*
                          * parent ".."
                          */
-                        filp->f_pos = 1;
+                        filp->f_pos = 2;
                         if (filldir(dirent, "..", 2, 1, PARENT(ip), DT_DIR))
                                 return 0;
 
@@ -3123,24 +3131,25 @@ int jfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
                 /*
                  * Legacy filesystem - OS/2 & Linux JFS < 0.3.6
                  *
-                 * pn = index = 0:      First entry "."
-                 * pn = 0; index = 1:   Second entry ".."
+                 * pn = 0; index = 1:   First entry "."
+                 * pn = 0; index = 2:   Second entry ".."
                  * pn > 0:              Real entries, pn=1 -> leftmost page
                  * pn = index = -1:     No more entries
                  */
                 dtpos = filp->f_pos;
-                if (dtpos == 0) {
+                if (dtpos < 2) {
                         /* build "." entry */
 
+                        filp->f_pos = 1;
                         if (filldir(dirent, ".", 1, filp->f_pos, ip->i_ino,
                                     DT_DIR))
                                 return 0;
-                        dtoffset->index = 1;
+                        dtoffset->index = 2;
                         filp->f_pos = dtpos;
                 }
 
                 if (dtoffset->pn == 0) {
-                        if (dtoffset->index == 1) {
+                        if (dtoffset->index == 2) {
                                 /* build ".." entry */
 
                                 if (filldir(dirent, "..", 2, filp->f_pos,
@@ -3233,6 +3242,12 @@ int jfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
                                         }
                                         jfs_dirent->position = unique_pos++;
                                 }
+                                /*
+                                 * We add 1 to the index because we may
+                                 * use a value of 2 internally, and NFSv4
+                                 * doesn't like that.
+                                 */
+                                jfs_dirent->position++;
                         } else {
                                 jfs_dirent->position = dtpos;
                                 len = min(d_namleft, DTLHDRDATALEN_LEGACY);