[PATCH] 2.5.4-pre1: further llseek cleanup (1/3)

This is the first of three patches implementing further llseek cleanup,
against 2.5.4-pre1.

The 'push locking into llseek methods' patch was integrated into 2.5.3.
The networking filesystems, however, do not protect i_size and can not
rely on the inode semaphore used in generic_file_llseek.

This patch implements a remote_llseek method, which is basically the
pre-2.5.3 version of generic_file_llseek.  Locking is done via the BKL.
When we have a saner locking system in place, we can push it into this
function in lieu.

Ncpfs, nfs, and smbfs have been converted to use this new llseek.

Note this is updated over the previous posted patch.

	Robert Love

fs/ncpfs/file.c

@@ -281,7 +281,7 @@ static int ncp_release(struct inode *inode, struct file *file) {
 
 struct file_operations ncp_file_operations =
 {
-	llseek:		generic_file_llseek,
+	llseek:		remote_llseek,
 	read:		ncp_file_read,
 	write:		ncp_file_write,
 	ioctl:		ncp_ioctl,

fs/nfs/file.c

@@ -41,7 +41,7 @@ static int  nfs_file_flush(struct file *);
 static int  nfs_fsync(struct file *, struct dentry *dentry, int datasync);
 
 struct file_operations nfs_file_operations = {
-	llseek:		generic_file_llseek,
+	llseek:		remote_llseek,
 	read:		nfs_file_read,
 	write:		nfs_file_write,
 	mmap:		nfs_file_mmap,

fs/read_write.c

@@ -51,6 +51,31 @@ loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
 	return retval;
 }
 
+loff_t remote_llseek(struct file *file, loff_t offset, int origin)
+{
+	long long retval;
+
+	lock_kernel();
+	switch (origin) {
+		case 2:
+			offset += file->f_dentry->d_inode->i_size;
+			break;
+		case 1:
+			offset += file->f_pos;
+	}
+	retval = -EINVAL;
+	if (offset>=0 && offset<=file->f_dentry->d_inode->i_sb->s_maxbytes) {
+		if (offset != file->f_pos) {
+			file->f_pos = offset;
+			file->f_reada = 0;
+			file->f_version = ++event;
+		}
+		retval = offset;
+	}
+	unlock_kernel();
+	return retval;
+}
+
 loff_t no_llseek(struct file *file, loff_t offset, int origin)
 {
 	return -ESPIPE;

fs/smbfs/file.c

@@ -381,7 +381,7 @@ smb_file_permission(struct inode *inode, int mask)
 
 struct file_operations smb_file_operations =
 {
-	llseek:		generic_file_llseek,
+	llseek:		remote_llseek,
 	read:		smb_file_read,
 	write:		smb_file_write,
 	ioctl:		smb_ioctl,

include/linux/fs.h

@@ -1461,6 +1461,7 @@ extern ssize_t generic_file_write(struct file *, const char *, size_t, loff_t *)
 extern void do_generic_file_read(struct file *, loff_t *, read_descriptor_t *, read_actor_t);
 extern loff_t no_llseek(struct file *file, loff_t offset, int origin);
 extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);
+extern loff_t remote_llseek(struct file *file, loff_t offset, int origin);
 extern ssize_t generic_read_dir(struct file *, char *, size_t, loff_t *);
 extern int generic_file_open(struct inode * inode, struct file * filp);
 

kernel/ksyms.c

@@ -251,6 +251,7 @@ EXPORT_SYMBOL(vfs_rename);
 EXPORT_SYMBOL(vfs_statfs);
 EXPORT_SYMBOL(generic_read_dir);
 EXPORT_SYMBOL(generic_file_llseek);
+EXPORT_SYMBOL(remote_llseek);
 EXPORT_SYMBOL(no_llseek);
 EXPORT_SYMBOL(__pollwait);
 EXPORT_SYMBOL(poll_freewait);