exportfs: Return the minimum required handle size

The exportfs encode handle function should return the minimum required
handle size. This helps user to find out the handle size by passing 0
handle size in the first step and then redoing to the call again with
the returned handle size value.

Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

12 files changed, 59 insertions, 18 deletions

diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
index ff27d7a477b2..b4ffad859adb 100644
--- a/fs/btrfs/export.c
+++ b/fs/btrfs/export.c
@@ -21,9 +21,13 @@ static int btrfs_encode_fh(struct dentry *dentry, u32 *fh, int *max_len,
         int len = *max_len;
         int type;
 
-        if ((len < BTRFS_FID_SIZE_NON_CONNECTABLE) ||
-            (connectable && len < BTRFS_FID_SIZE_CONNECTABLE))
+        if (connectable && (len < BTRFS_FID_SIZE_CONNECTABLE)) {
+                *max_len = BTRFS_FID_SIZE_CONNECTABLE;
                 return 255;
+        } else if (len < BTRFS_FID_SIZE_NON_CONNECTABLE) {
+                *max_len = BTRFS_FID_SIZE_NON_CONNECTABLE;
+                return 255;
+        }
 
         len  = BTRFS_FID_SIZE_NON_CONNECTABLE;
         type = FILEID_BTRFS_WITHOUT_PARENT;
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 4b6825740dd5..cfe55731b6dc 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -320,9 +320,14 @@ static int export_encode_fh(struct dentry *dentry, struct fid *fid,
         struct inode * inode = dentry->d_inode;
         int len = *max_len;
         int type = FILEID_INO32_GEN;
-        
-        if (len < 2 || (connectable && len < 4))
+
+        if (connectable && (len < 4)) {
+                *max_len = 4;
+                return 255;
+        } else if (len < 2) {
+                *max_len = 2;
                 return 255;
+        }
 
         len = 2;
         fid->i32.ino = inode->i_ino;
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 86753fe10bd1..0e277ec4b612 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -757,8 +757,10 @@ fat_encode_fh(struct dentry *de, __u32 *fh, int *lenp, int connectable)
         struct inode *inode =  de->d_inode;
         u32 ipos_h, ipos_m, ipos_l;
 
-        if (len < 5)
+        if (len < 5) {
+                *lenp = 5;
                 return 255; /* no room */
+        }
 
         ipos_h = MSDOS_I(inode)->i_pos >> 8;
         ipos_m = (MSDOS_I(inode)->i_pos & 0xf0) << 24;
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 9e3f68cc1bd1..051b1a084528 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -637,8 +637,10 @@ static int fuse_encode_fh(struct dentry *dentry, u32 *fh, int *max_len,
         u64 nodeid;
         u32 generation;
 
-        if (*max_len < len)
+        if (*max_len < len) {
+                *max_len = len;
                 return  255;
+        }
 
         nodeid = get_fuse_inode(inode)->nodeid;
         generation = inode->i_generation;
diff --git a/fs/gfs2/export.c b/fs/gfs2/export.c
index 9023db8184f9..b5a5e60df0d5 100644
--- a/fs/gfs2/export.c
+++ b/fs/gfs2/export.c
@@ -36,9 +36,13 @@ static int gfs2_encode_fh(struct dentry *dentry, __u32 *p, int *len,
         struct super_block *sb = inode->i_sb;
         struct gfs2_inode *ip = GFS2_I(inode);
 
-        if (*len < GFS2_SMALL_FH_SIZE ||
-            (connectable && *len < GFS2_LARGE_FH_SIZE))
+        if (connectable && (*len < GFS2_LARGE_FH_SIZE)) {
+                *len = GFS2_LARGE_FH_SIZE;
                 return 255;
+        } else if (*len < GFS2_SMALL_FH_SIZE) {
+                *len = GFS2_SMALL_FH_SIZE;
+                return 255;
+        }
 
         fh[0] = cpu_to_be32(ip->i_no_formal_ino >> 32);
         fh[1] = cpu_to_be32(ip->i_no_formal_ino & 0xFFFFFFFF);
diff --git a/fs/isofs/export.c b/fs/isofs/export.c
index ed752cb38474..dd4687ff30d0 100644
--- a/fs/isofs/export.c
+++ b/fs/isofs/export.c
@@ -124,9 +124,13 @@ isofs_export_encode_fh(struct dentry *dentry,
          * offset of the inode and the upper 16 bits of fh32[1] to
          * hold the offset of the parent.
          */
-
-        if (len < 3 || (connectable && len < 5))
+        if (connectable && (len < 5)) {
+                *max_len = 5;
+                return 255;
+        } else if (len < 3) {
+                *max_len = 3;
                 return 255;
+        }
 
         len = 3;
         fh32[0] = ei->i_iget5_block;
diff --git a/fs/ocfs2/export.c b/fs/ocfs2/export.c
index 5dbc3062b4fd..254652a9b542 100644
--- a/fs/ocfs2/export.c
+++ b/fs/ocfs2/export.c
@@ -197,8 +197,12 @@ static int ocfs2_encode_fh(struct dentry *dentry, u32 *fh_in, int *max_len,
                    dentry->d_name.len, dentry->d_name.name,
                    fh, len, connectable);
 
-        if (len < 3 || (connectable && len < 6)) {
-                mlog(ML_ERROR, "fh buffer is too small for encoding\n");
+        if (connectable && (len < 6)) {
+                *max_len = 6;
+                type = 255;
+                goto bail;
+        } else if (len < 3) {
+                *max_len = 3;
                 type = 255;
                 goto bail;
         }
diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
index 0bae036831e2..1bba24bad820 100644
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -1593,8 +1593,13 @@ int reiserfs_encode_fh(struct dentry *dentry, __u32 * data, int *lenp,
         struct inode *inode = dentry->d_inode;
         int maxlen = *lenp;
 
-        if (maxlen < 3)
+        if (need_parent && (maxlen < 5)) {
+                *lenp = 5;
                 return 255;
+        } else if (maxlen < 3) {
+                *lenp = 3;
+                return 255;
+        }
 
         data[0] = inode->i_ino;
         data[1] = le32_to_cpu(INODE_PKEY(inode)->k_dir_id);
diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index b7c338d5e9df..f1dce848ef96 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -1286,8 +1286,13 @@ static int udf_encode_fh(struct dentry *de, __u32 *fh, int *lenp,
         struct fid *fid = (struct fid *)fh;
         int type = FILEID_UDF_WITHOUT_PARENT;
 
-        if (len < 3 || (connectable && len < 5))
+        if (connectable && (len < 5)) {
+                *lenp = 5;
+                return 255;
+        } else if (len < 3) {
+                *lenp = 3;
                 return 255;
+        }
 
         *lenp = 3;
         fid->udf.block = location.logicalBlockNum;
diff --git a/fs/xfs/linux-2.6/xfs_export.c b/fs/xfs/linux-2.6/xfs_export.c
index fc0114da7fdd..f4f878fc0083 100644
--- a/fs/xfs/linux-2.6/xfs_export.c
+++ b/fs/xfs/linux-2.6/xfs_export.c
@@ -89,8 +89,10 @@ xfs_fs_encode_fh(
          * seven combinations work.  The real answer is "don't use v2".
          */
         len = xfs_fileid_length(fileid_type);
-        if (*max_len < len)
+        if (*max_len < len) {
+                *max_len = len;
                 return 255;
+        }
         *max_len = len;
 
         switch (fileid_type) {
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index 28028988c862..65afdfd31b7b 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -121,8 +121,10 @@ struct fid {
  *    set, the encode_fh() should store sufficient information so that a good
  *    attempt can be made to find not only the file but also it's place in the
  *    filesystem.   This typically means storing a reference to de->d_parent in
- *    the filehandle fragment.  encode_fh() should return the number of bytes
- *    stored or a negative error code such as %-ENOSPC
+ *    the filehandle fragment.  encode_fh() should return the fileid_type on
+ *    success and on error returns 255 (if the space needed to encode fh is
+ *    greater than @max_len*4 bytes). On error @max_len contains the minimum
+ *    size(in 4 byte unit) needed to encode the file handle.
  *
  * fh_to_dentry:
  *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
diff --git a/mm/shmem.c b/mm/shmem.c
index 5ee67c990602..3437b65d6d6e 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2144,8 +2144,10 @@ static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
 {
         struct inode *inode = dentry->d_inode;
 
-        if (*len < 3)
+        if (*len < 3) {
+                *len = 3;
                 return 255;
+        }
 
         if (inode_unhashed(inode)) {
                 /* Unfortunately insert_inode_hash is not idempotent,