From ca572727dbb945e443564029a495157fd2e72995 Mon Sep 17 00:00:00 2001
From: jan Blunck <jblunck@suse.de>
Date: Wed, 26 May 2010 14:44:53 -0700
Subject: fs/: do not fallback to default_llseek() when readdir() uses BKL

Do not use the fallback default_llseek() if the readdir operation of the
filesystem still uses the big kernel lock.

Since llseek() modifies
file->f_pos of the directory directly it may need locking to not confuse
readdir which usually uses file->f_pos directly as well

Since the special characteristics of the BKL (unlocked on schedule) are
not necessary in this case, the inode mutex can be used for locking as
provided by generic_file_llseek().  This is only possible since all
filesystems, except reiserfs, either use a directory as a flat file or
with disk address offsets.  Reiserfs on the other hand uses a 32bit hash
off the filename as the offset so generic_file_llseek() can get used as
well since the hash is always smaller than sb->s_maxbytes (= (512 << 32) -
blocksize).

Signed-off-by: Jan Blunck <jblunck@suse.de>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Anders Larsen <al@alarsen.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/autofs/root.c b/fs/autofs/root.c
index 8713c7c..9a0520b 100644
--- a/fs/autofs/root.c
+++ b/fs/autofs/root.c
@@ -28,6 +28,7 @@ static int autofs_root_mkdir(struct inode *,struct dentry *,int);
 static int autofs_root_ioctl(struct inode *, struct file *,unsigned int,unsigned long);
 
 const struct file_operations autofs_root_operations = {
+	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
 	.readdir	= autofs_root_readdir,
 	.ioctl		= autofs_root_ioctl,
diff --git a/fs/freevxfs/vxfs_lookup.c b/fs/freevxfs/vxfs_lookup.c
index aee049c..0ec7bb2 100644
--- a/fs/freevxfs/vxfs_lookup.c
+++ b/fs/freevxfs/vxfs_lookup.c
@@ -57,6 +57,8 @@ const struct inode_operations vxfs_dir_inode_ops = {
 };
 
 const struct file_operations vxfs_dir_operations = {
+	.llseek =		generic_file_llseek,
+	.read =			generic_read_dir,
 	.readdir =		vxfs_readdir,
 };
 
diff --git a/fs/isofs/dir.c b/fs/isofs/dir.c
index b9ab69b..e0aca9a 100644
--- a/fs/isofs/dir.c
+++ b/fs/isofs/dir.c
@@ -272,6 +272,7 @@ static int isofs_readdir(struct file *filp,
 
 const struct file_operations isofs_dir_operations =
 {
+	.llseek = generic_file_llseek,
 	.read = generic_read_dir,
 	.readdir = isofs_readdir,
 };
diff --git a/fs/ncpfs/dir.c b/fs/ncpfs/dir.c
index 92dde6f..9578cbe 100644
--- a/fs/ncpfs/dir.c
+++ b/fs/ncpfs/dir.c
@@ -49,6 +49,7 @@ extern int ncp_symlink(struct inode *, struct dentry *, const char *);
 		      
 const struct file_operations ncp_dir_operations =
 {
+	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
 	.readdir	= ncp_readdir,
 	.unlocked_ioctl	= ncp_ioctl,
diff --git a/fs/qnx4/dir.c b/fs/qnx4/dir.c
index 6f30c3d..3d3fd46 100644
--- a/fs/qnx4/dir.c
+++ b/fs/qnx4/dir.c
@@ -77,6 +77,7 @@ out:
 
 const struct file_operations qnx4_dir_operations =
 {
+	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
 	.readdir	= qnx4_readdir,
 	.fsync		= simple_fsync,
diff --git a/fs/reiserfs/dir.c b/fs/reiserfs/dir.c
index 0793044..4455fbe 100644
--- a/fs/reiserfs/dir.c
+++ b/fs/reiserfs/dir.c
@@ -18,6 +18,7 @@ static int reiserfs_dir_fsync(struct file *filp, struct dentry *dentry,
 			      int datasync);
 
 const struct file_operations reiserfs_dir_operations = {
+	.llseek = generic_file_llseek,
 	.read = generic_read_dir,
 	.readdir = reiserfs_readdir,
 	.fsync = reiserfs_dir_fsync,
diff --git a/fs/smbfs/dir.c b/fs/smbfs/dir.c
index 6c97842..00a70ca 100644
--- a/fs/smbfs/dir.c
+++ b/fs/smbfs/dir.c
@@ -37,6 +37,7 @@ static int smb_link(struct dentry *, struct inode *, struct dentry *);
 
 const struct file_operations smb_dir_operations =
 {
+	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
 	.readdir	= smb_readdir,
 	.unlocked_ioctl	= smb_ioctl,
diff --git a/fs/udf/dir.c b/fs/udf/dir.c
index 3a84455..1660c81 100644
--- a/fs/udf/dir.c
+++ b/fs/udf/dir.c
@@ -207,6 +207,7 @@ static int udf_readdir(struct file *filp, void *dirent, filldir_t filldir)
 
 /* readdir and lookup functions */
 const struct file_operations udf_dir_operations = {
+	.llseek			= generic_file_llseek,
 	.read			= generic_read_dir,
 	.readdir		= udf_readdir,
 	.unlocked_ioctl		= udf_ioctl,
-- 
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