[PATCH] bdev: use correct mapping's i_sem

From: viro@parcelfarce.linux.theplanet.co.uk <viro@parcelfarce.linux.theplanet.co.uk>

In a bunch of places we used file->f_dentry->d_inode->i_sem to protect
fdatasync et.al.  Replaced with corrent file->f_mapping->host->i_sem - the
object we are protecting is address_space, so we want an exclusion that would
work for redirected ->i_mapping.  For normal files (not coda, not bdev) it's
all the same, of course - there we have

 	file->f_mapping->host == file->f_dentry->d_inode

and change above is an equivalent transfromation.

fs/buffer.c

@@ -314,8 +314,7 @@ int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
 asmlinkage long sys_fsync(unsigned int fd)
 {
 	struct file * file;
-	struct dentry * dentry;
-	struct inode * inode;
+	struct address_space *mapping;
 	int ret, err;
 
 	ret = -EBADF;
@@ -323,8 +322,7 @@ asmlinkage long sys_fsync(unsigned int fd)
 	if (!file)
 		goto out;
 
-	dentry = file->f_dentry;
-	inode = dentry->d_inode;
+	mapping = file->f_mapping;
 
 	ret = -EINVAL;
 	if (!file->f_op || !file->f_op->fsync) {
@@ -333,17 +331,17 @@ asmlinkage long sys_fsync(unsigned int fd)
 	}
 
 	/* We need to protect against concurrent writers.. */
-	down(&inode->i_sem);
+	down(&mapping->host->i_sem);
 	current->flags |= PF_SYNCWRITE;
-	ret = filemap_fdatawrite(inode->i_mapping);
-	err = file->f_op->fsync(file, dentry, 0);
+	ret = filemap_fdatawrite(mapping);
+	err = file->f_op->fsync(file, file->f_dentry, 0);
 	if (!ret)
 		ret = err;
-	err = filemap_fdatawait(inode->i_mapping);
+	err = filemap_fdatawait(mapping);
 	if (!ret)
 		ret = err;
 	current->flags &= ~PF_SYNCWRITE;
-	up(&inode->i_sem);
+	up(&mapping->host->i_sem);
 
 out_putf:
 	fput(file);
@@ -354,8 +352,7 @@ asmlinkage long sys_fsync(unsigned int fd)
 asmlinkage long sys_fdatasync(unsigned int fd)
 {
 	struct file * file;
-	struct dentry * dentry;
-	struct inode * inode;
+	struct address_space *mapping;
 	int ret, err;
 
 	ret = -EBADF;
@@ -363,24 +360,23 @@ asmlinkage long sys_fdatasync(unsigned int fd)
 	if (!file)
 		goto out;
 
-	dentry = file->f_dentry;
-	inode = dentry->d_inode;
-
 	ret = -EINVAL;
 	if (!file->f_op || !file->f_op->fsync)
 		goto out_putf;
 
-	down(&inode->i_sem);
+	mapping = file->f_mapping;
+
+	down(&mapping->host->i_sem);
 	current->flags |= PF_SYNCWRITE;
-	ret = filemap_fdatawrite(inode->i_mapping);
-	err = file->f_op->fsync(file, dentry, 1);
+	ret = filemap_fdatawrite(mapping);
+	err = file->f_op->fsync(file, file->f_dentry, 1);
 	if (!ret)
 		ret = err;
-	err = filemap_fdatawait(inode->i_mapping);
+	err = filemap_fdatawait(mapping);
 	if (!ret)
 		ret = err;
 	current->flags &= ~PF_SYNCWRITE;
-	up(&inode->i_sem);
+	up(&mapping->host->i_sem);
 
 out_putf:
 	fput(file);

fs/nfs/file.c

@@ -266,7 +266,7 @@ nfs_file_write(struct kiocb *iocb, const char *buf, size_t count, loff_t pos)
 int
 nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
 {
-	struct inode * inode = filp->f_dentry->d_inode;
+	struct inode * inode = filp->f_mapping->host;
 	int	status = 0;
 	int	status2;
 
@@ -309,13 +309,13 @@ nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
 	 * Flush all pending writes before doing anything
 	 * with locks..
 	 */
-	status = filemap_fdatawrite(inode->i_mapping);
+	status = filemap_fdatawrite(filp->f_mapping);
 	down(&inode->i_sem);
 	status2 = nfs_wb_all(inode);
 	if (!status)
 		status = status2;
 	up(&inode->i_sem);
-	status2 = filemap_fdatawait(inode->i_mapping);
+	status2 = filemap_fdatawait(filp->f_mapping);
 	if (!status)
 		status = status2;
 	if (status < 0)
@@ -335,11 +335,11 @@ nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
 	 */
  out_ok:
 	if ((IS_SETLK(cmd) || IS_SETLKW(cmd)) && fl->fl_type != F_UNLCK) {
-		filemap_fdatawrite(inode->i_mapping);
+		filemap_fdatawrite(filp->f_mapping);
 		down(&inode->i_sem);
 		nfs_wb_all(inode);      /* we may have slept */
 		up(&inode->i_sem);
-		filemap_fdatawait(inode->i_mapping);
+		filemap_fdatawait(filp->f_mapping);
 		nfs_zap_caches(inode);
 	}
 	return status;

mm/filemap.c

@@ -1970,7 +1970,7 @@ EXPORT_SYMBOL(generic_file_readv);
 ssize_t generic_file_writev(struct file *file, const struct iovec *iov,
 			unsigned long nr_segs, loff_t * ppos) 
 {
-	struct inode *inode = file->f_dentry->d_inode;
+	struct inode *inode = file->f_mapping->host;
 	ssize_t ret;
 
 	down(&inode->i_sem);

mm/msync.c

@@ -146,20 +146,20 @@ static int msync_interval(struct vm_area_struct * vma,
 		ret = filemap_sync(vma, start, end-start, flags);
 
 		if (!ret && (flags & MS_SYNC)) {
-			struct inode *inode = file->f_dentry->d_inode;
+			struct address_space *mapping = file->f_mapping;
 			int err;
 
-			down(&inode->i_sem);
-			ret = filemap_fdatawrite(inode->i_mapping);
+			down(&mapping->host->i_sem);
+			ret = filemap_fdatawrite(mapping);
 			if (file->f_op && file->f_op->fsync) {
 				err = file->f_op->fsync(file,file->f_dentry,1);
 				if (err && !ret)
 					ret = err;
 			}
-			err = filemap_fdatawait(inode->i_mapping);
+			err = filemap_fdatawait(mapping);
 			if (!ret)
 				ret = err;
-			up(&inode->i_sem);
+			up(&mapping->host->i_sem);
 		}
 	}
 	return ret;