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>

8 files changed, 9 insertions, 0 deletions

diff --git a/fs/autofs/root.c b/fs/autofs/root.c
index 8713c7cfbc79..9a0520b50663 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 aee049cb9f84..0ec7bb2c95c6 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 b9ab69b3a482..e0aca9a0ac68 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 92dde6f8d893..9578cbe0cd58 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 6f30c3d5bcbf..3d3fd4692133 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 07930449a958..4455fbe269a3 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 6c978428892d..00a70cab1f36 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 3a84455c2a77..1660c81ffa3d 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,