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Commit ca572727 authored by jan Blunck's avatar jan Blunck Committed by Linus Torvalds
Browse files

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: default avatarJan Blunck <jblunck@suse.de>
Acked-by: default avatarJan Kara <jack@suse.cz>
Acked-by: default avatarAnders Larsen <al@alarsen.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b4d878e2

fs/autofs/root.c

+1 −0
Original line number Diff line number Diff line
@@ -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,

fs/freevxfs/vxfs_lookup.c

+2 −0
Original line number Diff line number Diff line
@@ -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,

};

fs/isofs/dir.c

+1 −0
Original line number Diff line number Diff line
@@ -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,

};

fs/ncpfs/dir.c

+1 −0
Original line number Diff line number Diff line
@@ -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,

fs/qnx4/dir.c

+1 −0
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ static int qnx4_readdir(struct file *filp, void *dirent, filldir_t filldir) 


const struct file_operations qnx4_dir_operations =

{

	.llseek		= generic_file_llseek,

	.read		= generic_read_dir,

	.readdir	= qnx4_readdir,

	.fsync		= simple_fsync,